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Sample records for changing redox conditions

  1. Modeling CO2 sediment-water flux variations connected with changes of redox conditions

    NASA Astrophysics Data System (ADS)

    Yakushev, Evgeniy; Protsenko, Elizaveta

    2013-04-01

    Changes of bottom redox conditions from oxic to hypoxic, suboxic and anoxic affect rates of sediment-water fluxes of chemical parameters, i.e. oxygen, nutrient (including carbon), redox metals. Chemosynthetic organic matter production in suboxic and anoxic conditions additionally affects transformation of carbon. This work aimed in estimation of a potential influence of changes of the bottom redox conditions on the sediment -water fluxes of carbon. We use a 1-dimensional C-N-P-Si-O-S-Mn-Fe vertical transport-reaction model describing both the sediments and bottom boundary layers coupled with biogeochemical block simulating changeable redox conditions, and the carbonate system processes block. A biogeochemical block is based on ROLM (RedOx Layer Model), that was constructed to simulate basic features of the water column biogeochemical structure changes in oxic, anoxic and changeable conditions (Yakushev et al., 2007). Organic matter formation and decay, reduction and oxidation of species of nitrogen, sulfur, manganese, iron, and the transformation of phosphorus species are parameterized in the model. The model includes blocks for phytoplankton, zooplankton, aerobic autotrophic and heterotrophic bacteria and anaerobic autotrophic and heterotrophic bacteria. In this study we additionally parameterized transformation of Si and C and forms of alkalinity. We simulate changes in the bottom boundary layer pH in different redox conditions under the same leakage scenario.

  2. 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.

  3. Redox Conditions and Related Color Change in Eastern Equatorial Pacific Sediments: IODP Site U1334

    NASA Astrophysics Data System (ADS)

    Kordesch, W. E.; Gussone, N. C.; Hathorne, E. C.; Kimoto, K.; Delaney, M. L.

    2011-12-01

    This study was prompted by a 65 m thick brown-green color change in deep-sea sediments of IODP Site U1334 (0-38 Ma, 4799 m water depth) that corresponds to its equatorial crossing (caused by the Northward movement of the pacific plate). Green sediment is a visual indicator of reducing conditions in sediment due to enhanced organic matter deposition and burial. Here we use geochemical redox indicators to characterize the effect of equatorial upwelling on bottom water. The modern redox signal is captured in porewater profiles (nitrate, manganese, iron, sulfate) while trace metal Enrichment Factors (EF) in bulk sediment (manganese, uranium, molybdenum, rhenium) normalized to the detrital component (titanium) record redox state at burial. To measure export productivity we also measure biogenic barium. Porewater profiles reveal suboxic diagenesis; profiles follow the expected sequence of nitrate, manganese oxide, and iron oxide reduction with increasing depth. Constant sulfate (~28 μM) implies anoxia has not occurred. Bulk sediment Mn EF are enriched (EF > 1) throughout the record (Mn EF = 15-200) while U and Mo enrichment corresponds to green color and equatorial proximity (U EF = 4-19; Mo EF = 0-7). Constant Mn enrichment implies continuous oxygenation. Uranium and Mo enrichment near the equator represents suboxic conditions also seen in the porewater. Low Re concentrations (below detection) provide additional evidence against anoxia. A comparison of Mn EF from total digestions to samples treated with an additional reductive cleaning step distinguishes between Mn-oxides and Mn-carbonates, indicating oxygenated and reducing conditions respectively. Mn-carbonate occurrence agrees with U and Mo EF; conditions were more reducing near the equator. Bio-Ba shows significant variability over this interval (22-99 mmol g-1). Our geochemical results indicate that bottom waters became suboxic at the equator as a result of equatorial upwelling-influenced increases in organic

  4. 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

  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. Trace Metal Evidence for Changes in Redox Conditions Across Transitions From Terrigenous Clay to Diatomaceous Sediment, Saanich Inlet, B.C.

    NASA Astrophysics Data System (ADS)

    Morford, J. L.; Russell, A. D.; Emerson, S.

    2001-05-01

    Redox-sensitive metals can be used to discern subtle changes in redox conditions, beyond those evident from the visual sedimentary record. We measured the concentrations of redox sensitive metals (Mn, V, Mo, U, Cd and Re) in sediments from ODP Leg 169S hole 1033B in Saanich Inlet, British Columbia, to determine changes in redox conditions associated with the onset of laminated sediments at 12.5 kyr. The most striking result is a maximum in authigenic Re (19 ppb) along with detrital levels of Mo at the glacial terrigenous clay-diatomaceous sediment transition. In contrast, the underlying glacial terrigenous clay, which extends throughout the bottom section of the core, is chemically similar to detrital values from either measured metal concentrations in Cowichan River particulates or average shale literature values. These data suggest a period of oxic bottom waters but reducing pore waters. This could be due to the dramatic transformation of Saanich Inlet during the late deglaciation from an open bay to an inlet, which restricted circulation and slowed bottom water oxygen renewal. A peak and gradual increase in authigenic Mn in younger sediments suggests that increasingly oxic conditions followed the authigenic enrichment in Re. These conditions could be connected to the Younger Dryas cooling period, which was coincident with an increase in well-oxygenated upwelled waters on the west coast of North America that form the bottom waters of Saanich Inlet. Metal concentrations in a gray clay bed at approximately 11 kyr are similar to their concentrations in glacial terrigenous clay, implying that they have a common source. Authigenic enrichments of Re with little authigenic Mo and Cd suggest that before the deposition of the clay section bottom waters were oxic but pore waters were reducing. Laminations, higher authigenic Mo and Cd, and slightly lower Re/Mo ratios above the clay layer suggest anoxic conditions. These results are consistent with increased stratification

  10. 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

  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. Changes of redox activity during the development of rape.

    PubMed

    Filek, Maria; Mirek, Magdalena; Długolecka, Monika

    2006-01-01

    Redox activity was measured in vegetative and generative apical parts (5 mm of the stem) and youngest leaves of winter (cv. "G6rczański") and spring (cv. "Młochowski") rape. Both genotypes were cultured under the same growth conditions (17/15 degrees C day/night, 16 h photo-period), but winter rape was additionally vernalized (5/2 degrees C day/night, 56 days) in order to induce the generative development. The cyclic voltammetric method was used to measure the redox potential of samples in the presence of Fe3+ ions. Changes in the redox activity were compared with changes in riboflavin content and activities of antioxidative enzymes: superoxide dismutase (SOD) and catalase (CAT). The higher level of Fe3+ ions and riboflavin detected in generative apices and leaves of winter and spring varieties indicated that electrons (and their donors) were present at a lower level in these organs in comparison with the vegetative ones. On the contrary, SOD and CAT activity were lower in generative than in vegetative organs. This confirms changes in the redox balance and involvement of oxygen radicals in the generative development of rape plants. The similarity of the measured parameters between winter and spring varieties indicates that the observed changes are independent of the way of generative induction (vernalization). Riboflavin can serve as one of the electron carriers between other oxidation-reduction substances.

  13. 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

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

    NASA Astrophysics Data System (ADS)

    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.

  15. 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.

  16. INFLUENCE OF PH AND REDOX CONDITIONS ON COPPER LEACHING

    EPA Science Inventory

    Leaching behavior of metals from a mineral processing waste at varying pH and redox conditions was studies. Effect of combinations of pH and Eh on leaching of copper is described. Leaching of copper was found to be dependent on both pH and Eh. Higher concentrations of Cu were ...

  17. 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

  18. 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.

  19. 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

  20. 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.

  1. 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

  2. Evolution of Redox Conditions and Groundwater Composition in Recharge-Discharge Environments on the Canadian Shield

    NASA Astrophysics Data System (ADS)

    Gascoyne, M.

    1997-03-01

    The composition of groundwater in fractured crystalline rocks of the Canadian Shield evolves along flow paths from recharge to discharge in response to interactions with bedrock and fracture-filling minerals, and by dissolution of soluble (Cl-rich) salts in the rock matrix. The groundwater redox potential changes from oxidizing to reducing conditions due, initially, to rapid consumption of dissolved oxygen by organics in the upper ˜100 m of bedrock and, subsequently, to interaction with rock minerals. Measured Eh values of deep groundwater in the granitic Lac du Bonnet batholith in southeastern Manitoba indicate that the Fe(II)/Fe(III) couple controls groundwater redox potential. This conclusion is supported by other geochemical characteristics, such as absence of CH4, H2S, H2, NO3 and abundance of SO4. These observations are important in selecting a suitable site for disposal of nuclear fuel wastes. Further evidence of the evolution of redox conditions is given by variations in uranium concentration, which range from about 1,000μg/L in dilute near-surface groundwater to <1 μg/L in some deep, saline groundwaters. Groundwater at about 400 m depth in a recharge area on the Lac du Bonnet batholith contains significantly more uranium than groundwater farther along the flow path or near-surface in discharge areas. Uranium concentration is a useful and sensitive indicator of redox conditions.

  3. 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

  4. 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.

  5. 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.

  6. 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

  7. 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

  8. Hypothetical Modeling of Redox Conditions Within a Complex Ground-Water Flow Field in a Glacial Setting

    USGS Publications Warehouse

    Feinstein, Daniel T.; Thomas, Mary Ann

    2009-01-01

    This report describes a modeling approach for studying how redox conditions evolve under the influence of a complex ground-water flow field. The distribution of redox conditions within a flow system is of interest because of the intrinsic susceptibility of an aquifer to redox-sensitive, naturally occurring contaminants - such as arsenic - as well as anthropogenic contaminants - such as chlorinated solvents. The MODFLOW-MT3D-RT3D suite of code was applied to a glacial valley-fill aquifer to demonstrate a method for testing the interaction of flow patterns, sources of reactive organic carbon, and availability of electron acceptors in controlling redox conditions. Modeling results show how three hypothetical distributions of organic carbon influence the development of redox conditions in a water-supply aquifer. The distribution of strongly reduced water depends on the balance between the rate of redox reactions and the capability of different parts of the flow system to transmit oxygenated water. The method can take account of changes in the flow system induced by pumping that result in a new distribution of reduced water.

  9. 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.

  10. Measuring redox changes in vivo in leaves: prospects and technical challenges.

    PubMed

    Mullineaux, Philip M; Lawson, Tracy

    2008-01-01

    In leaves, the functioning of many key proteins under conditions promoting oxidative stress depends to a large extent on the redox potential of the glutathione couple. Routine measurements of the glutathione pool in leaves are destructive and labor-intensive processes that tend to underestimate the redox state. Therefore, a challenge for plant scientists is to develop a tool capable of measuring the redox state of the glutathione couple spatially (at different levels of resolution) and temporally in tissues and subcellular compartments in vivo. This chapter highlights the possibilities of using redox-sensitive green fluorescence proteins (roGFPs) as real-time redox reporters for use in intact plants and focuses on practical assessments of using such bioindicators in different leaf cell types subjected to environmental change. The advantages and shortcomings of different GFP variants are discussed along with the choice of system for leaves and possible approaches to overcoming some of the problems. We consider roGFP1-12 as an ideal candidate for developing a redox reporter system in whole plants because it has several advantages over the other variants, with dual excitation peaks allowing a ratiometric approach, insensitivity to pH and halide ions, increased response times for real-time measurements, and appropriate emission wavelengths for use in leaves. We conclude that when using roGFP1-12 with specific cell promotors, it would be possible to target distinct cell compartments and tissues and monitor changes in glutathione redox state to determine the effects of reactive oxygen species on specific cellular components.

  11. Evaluation of TCDD biodegradability under different redox conditions.

    PubMed

    Kao, C M; Chen, S C; Liu, J K; Wu, M J

    2001-09-01

    Polychlorinated dibenzo-p-dioxins have been generated as unwanted by-products in many industrial processes. Although their widespread distribution in different environmental compartments has been recognized, little is known about their fate in the ultimate environment sinks. The highly stable dioxin isomer 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) has been called the most toxic compound known to man. In this laboratory microcosm study, TCDD bioavailability was evaluated under five reduction/oxidation (redox) conditions including aerobic biodegradation, aerobic cometabolism, methanogenesis, iron reduction, and reductive dechlorination. Activated sludge and aquifer sediments from a TCDD and a pentachlorophenol (PCP) contaminated site were used as the inocula. Acetate, sludge cake, and cane molasses were used as the primary substrates (carbon sources) in cometabolism and reductive dechlorination microcosms. After a 90-day incubation period, microcosms constructed under reductive dechlorination conditions were the only treatment showing promising remediation results. The highest TCDD degradation rate [up to 86% of TCDD removal (with an initial concentration of 96 microg/kg of soil)] was observed in the microcosms with anaerobic activated sludge as the microbial inocula and sludge cakes as the primary substrates. Except for reductive dechlorination microcosms, no significant TCDD removal was observed in the microcosms prepared under other conditions. Thus, application of an effective primary substrate to enhance the reductive dechlorination process is a feasible method for TCDD bioremediation. Bioremediation expense can be significantly reduced by the supplement of some less expensive alternative substrates (e.g., sludge cakes, cane molasses). Results would be useful in designing a scale-up in situ or on-site bioremediation system such as bioslurry reactor for field application.

  12. Tracing Abiotic Redox Reaction Pathways From Changes in Loess Magnetism

    NASA Astrophysics Data System (ADS)

    Lagroix, F.; Guyodo, Y. J.

    2009-12-01

    Loess magnetism has thrived over the last thirty years and has produced valuable paleoclimate records and provided many insights into past climate on continental surfaces. One major hurdle remaining is the quantification of loess magnetism to climate or environment connection(s). Previous studies by others have revealed a relationship in top soils developing over loess in China, the Russian Steppe and the Midwest US between the enhanced magnetism, with respect to the underlying parent loess, and present day rainfall. However from one area to another the relationship differs and therefore whether the relationship observed in for the topsoil at a given site holds for the underlying paleosols is uncertain and difficult to verify. Our efforts are focused here on tracing the abiotic redox reaction pathways of natural samples of parent loess and of its overlying topsoil and underlying paleosol from changes in their magnetic behavior at low-temperature. By forcing the natural samples to their limits, i.e., most oxidized and most reduced states, under controlled laboratory conditions, our goal is to determine the range of alteration and its impact on the bulk magnetic properties. Moreover, by cycling from one end-member state to the other, the pathway of alteration is traced and whether this pathway is reversible or hysteretic is revealed. Our approach is voluntarily simplistic, involving a limited number of variables. Experiments are all conducted at 250°C and in air for oxidizing experiments or a mixture of carbon monoxide (20 %) and carbon dioxide (80 %) for reduction experiments. Starting sample type is the only variable that changes introducing increasing complexity as we go from the parent loess to the paleosol to the topsoil samples with, for example, increasing amounts of organic matter and clays.

  13. 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.

  14. 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.

  15. Modeling basic features of biogeochemical structure of water column, bottom boundary layer and benthic boundary layer in changeable redox conditions

    NASA Astrophysics Data System (ADS)

    Yakushev, Evgeniy

    2013-04-01

    Climate Change affects oxygen depletion and leads to spreading of the bottom areas with hypoxic and anoxic conditions in the coastal areas of the seas and inland waters. This work aimed in estimation of a role of changes of redox conditions in the biogeochemical structure there. We use a 1-dimensional C-N-P-Si-O-S-Mn-Fe vertical transport-reaction model describing the water column, bottom boundary layer and benthic boundary layer with biogeochemical block simulating redox conditions changeability. A biogeochemical block is based on ROLM (RedOx Layer Model), that was constructed to simulate basic features of the water column biogeochemical structure changes in oxic, anoxic and changeable conditions (Yakushev et al., 2007). Organic matter formation and decay, reduction and oxidation of species of nitrogen, sulfur, manganese, iron, and the transformation of phosphorus species are parameterized in the model. ROLM includes a simplified ecological model with phytoplankton, zooplankton, aerobic autotrophic and heterotrophic bacteria, anaerobic autotrophic and heterotrophic bacteria. We simulate changes in the parameters distributions and fluxes connected with the vertical displacement of redox interface from the sediments to the water.

  16. 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.

  17. Neptunium redox behavior and solubility in J-13 conditions

    SciTech Connect

    Efurd, D.W.; Runde, W.; Tait, C.D.

    1997-08-01

    In order to confirm that the redox reaction Np(V) to Np(IV) may occur, studies are being conducted including exposure of Np(V) to solutions of known E{sub h} vs pH, temperature. Analytic results from ongoing solubility experiments from undersaturation, using Np solids formed in previous oversaturation experiments, are reported.

  18. 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).

  19. 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,

  20. 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).

  1. Field scale heterogeneity of redox conditions in till-upscaling to a catchment nitrate model

    NASA Astrophysics Data System (ADS)

    Hansen, J. R.; Ernstsen, V.; Refsgaard, J. C.; Hansen, S.

    2008-11-01

    Point scale studies in different settings of glacial geology show a large local variation of redox conditions. There is a need to develop an upscaling methodology for catchment scale models. This paper describes a study of field-scale heterogeneity of redox-interfaces in a till aquitard within an area of 600 × 600 m. The results showed significant variation of the depths to the redox-interface and thickness of the aquitard. Nitrate was present above the redox-interface but reduced to non-detectable levels a few metres below the interface. An upscaling approach for an area of 92 km2 is proposed. Two models are proposed to predict the depth to the redox-interface in the aquitard and the resulting nitrate recharge concentrations to an underlying aquifer. The first model assumes that the depth to the redox-interface reflects the hydraulic head in the aquitard, and the second model assumes that the depth of the redox-interface is randomly distributed according to a log-normal probability distribution function. The upscaling approach using the random redox model estimated recharge concentrations comparable to the observed concentration in the underlying aquifer. The presented upscaling approach is applicable in distributed catchment models where sub-grid variability cannot be represented by the large grids.

  2. 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. PMID:26711280

  3. 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.

  4. 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...

  5. Experimental evidence of biomineralisation for three benthic foraminiferal species under different redox conditions: implications for paleo-redox proxies interpretation

    NASA Astrophysics Data System (ADS)

    Nardelli, Maria Pia; Barras, Christine; Metzger, Edouard; Filipsson, Helena; Jorissen, Frans; Geslin, Emmanuelle

    2014-05-01

    Foraminifera are among the most used group of organisms for paleoceanographic and paleoenvironmental reconstructions thanks to their ability to fossilize and the preservation potential in marine sediments. Calibrations of foraminiferal-based proxies are therefore of crucial importance for precise reconstructions together with uncertainty estimates of paleoenvironments; experimental approaches are increasingly used to deepen the understanding of biological and ecological aspects of biomineralization that can influence shell geochemistry. Some of the most important and still unanswered questions are: under which circumstances can foraminiferal biomineralization take place? Can their shells record different oxygenation levels and redox fronts migrations at the sediment-water interface? The hypothesis of their ability to biomineralise even in absence of oxygen was investigated in an experimental study. Calcein-labeled specimens of three benthic foraminiferal species, Ammonia tepida, Bulimina marginata and Cassidulina laevigata were introduced in different sediment layers of reconstituted cores (up to 10 cm depth). The sediment layers were separated by 100 µm mesh-size nets preventing specimen migrations. We could therefore evaluate the ability of the species to calcify at different redox fronts in the sediment. The results show that all species were able to calcify within 2 months in hypoxic. Two of them (Ammonia tepida and Bulimina marginata) are also able to calcify in completely anoxic conditions. The result suggests that foraminifera could register in their calcareous shells the migration of redox fronts associated to bottom-water oxygen depletions and anoxic events. With the help of microanalytical tools it will potentially be possible to reconstruct past oxygen levels with much higher accuracy and precision and to obtain proxies of completely anoxic conditions.

  6. 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. PMID:27380074

  7. 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

  8. 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

  9. 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

  10. Sediment trace metals as a recorder of bottom water redox conditions in the Baltic Sea over the Holocene

    NASA Astrophysics Data System (ADS)

    Slomp, C. P.; Jilbert, T.; van Riel, K. P. G. L.; Mort, H. P.; Conley, D. J.; Gustafsson, B. G.

    2012-04-01

    Increased inputs of nutrients from waste water and fertilizer have driven enhanced algal growth in the surface waters of the Baltic Sea over the past century. The sinking of this organic matter to the seafloor and subsequent decay has led to an oxygen demand in the bottom water that outpaces oxygen supply. Water column records indicate that this has resulted in a major redox shift in bottom water conditions from oxic to sulfidic (euxinic) in the late 1970's and early 1980's. Here, we show that this redox shift is recorded in sediment trace metal records throughout the Baltic Proper. We demonstrate that while rhenium (Re) tracks suboxia, molybdenum (Mo) is an accurate indicator of euxinia in the Baltic Sea. We subsequently use sediment Mo data for two long cores to assess changes in redox conditions over the Holocene. At one site, our results confirm earlier work showing three distinct periods of bottom water euxinia, namely during modern and medieval times and the early Holocene. The second site, in contrast, was euxinic throughout most of the Holocene. We suggest that the variable trends in redox observed at the first site are representative for most of the Baltic Proper and long-term bottom water euxinia in the Baltic Sea is limited to several small restricted basins.

  11. Arsenic distribution and speciation near rice roots influenced by iron plaques and redox conditions of the soil matrix.

    PubMed

    Yamaguchi, Noriko; Ohkura, Toshiaki; Takahashi, Yoshio; Maejima, Yuji; Arao, Tomohito

    2014-01-01

    Elevated arsenic (As) concentrations in rice and the soil solution result from changes in soil redox conditions, influenced by the water management practices during rice cultivation. Microscale changes in redox conditions from rhizosphere to soil matrix affect the As speciation and Fe plaque deposition. In order to focus on the rhizosphere environment, we observed microscale distribution and speciation of As around the rhizosphere of paddy rice with X-ray fluorescence mapping and X-ray absorption spectroscopy. When the soil matrix was anaerobic during rice growth, Fe-plaque did not cover the entire root, and As(III) was the dominant arsenic species in the soil matrix and rhizosphere. Draining before harvest led the conditions to shift to aerobic. Oxidation of As(III) to As(V) occurred faster in the Fe-plaque than the soil matrix. Arsenic was scavenged by iron mottles originating from Fe-plaque around the roots. The ratio of As(V) to As(III) decreased toward the outer-rim of the subsurface Fe mottles where the soil matrix was not completely aerated. These results provide direct evidence that speciation of As near rice roots depends on spatial and temporal redox variations in the soil matrix. PMID:24384039

  12. Electrode effects on temporal changes in electrolyte pH and redox potential for water treatment

    PubMed Central

    Ciblak, Ali; Mao, Xuhui; Padilla, Ingrid; Vesper, Dorothy; Alshawabkeh, Iyad; Alshawabkeh, Akram N.

    2012-01-01

    The performance of electrochemical remediation methods could be optimized by controlling the physicochemical conditions of the electrochemical redox system. The effects of anode type (reactive or inert), current density and electrolyte composition on the temporal changes in pH and redox potential of the electrolyte were evaluated in divided and mixed electrolytes. Two types of electrodes were used: iron as a reactive electrode and mixed metal oxide coated titanium (MMO) as an inert electrode. Electric currents of 15, 30, 45 and 60 mA (37.5 mA L−1, 75 mA L−1, 112.5 mA L−1 and 150 mA L−1) were applied. Solutions of NaCl, Na2SO4 and NaHCO3 were selected to mimic different wastewater or groundwater composition. Iron anodes resulted in highly reducing electrolyte conditions compared to inert anodes. Electrolyte pH was dependent on electrode type, electrolyte composition and current density. The pH of mixed-electrolyte was stable when MMO electrodes were used. When iron electrodes were used, the pH of electrolyte with relatively low current density (37.5 mA L−1) did not show significant changes but the pH increased sharply for relatively high current density (150 mA L−1). Sulfate solution showed more basic and relatively more reducing electrolyte condition compared to bicarbonate and chloride solution. The study shows that a highly reducing environment could be achieved using iron anodes in divided or mixed electrolytes and the pH and redox potential could be optimized by using appropriate current and polarity reversal. PMID:22416866

  13. Electrode effects on temporal changes in electrolyte pH and redox potential for water treatment.

    PubMed

    Ciblak, Ali; Mao, Xuhui; Padilla, Ingrid; Vesper, Dorothy; Alshawabkeh, Iyad; Alshawabkeh, Akram N

    2012-01-01

    The performance of electrochemical remediation methods could be optimized by controlling the physicochemical conditions of the electrochemical redox system. The effects of anode type (reactive or inert), current density and electrolyte composition on the temporal changes in pH and redox potential of the electrolyte were evaluated in divided and mixed electrolytes. Two types of electrodes were used: iron as a reactive electrode and mixed metal oxide coated titanium (MMO) as an inert electrode. Electric currents of 15, 30, 45 and 60 mA (37.5 mA L(-1), 75 mA L(-1), 112.5 mA L(-1) and 150 mA L(-1)) were applied. Solutions of NaCl, Na(2)SO(4) and NaHCO(3) were selected to mimic different wastewater or groundwater compositions. Iron anodes resulted in highly reducing electrolyte conditions compared to inert anodes. Electrolyte pH was dependent on electrode type, electrolyte composition and current density. The pH of mixed-electrolyte was stable when MMO electrodes were used. When iron electrodes were used, the pH of electrolyte with relatively low current density (37.5 mA L(-1)) did not show significant changes but the pH increased sharply for relatively high current density (150 mA L(-1)). Sulfate solution showed more basic and relatively more reducing electrolyte conditions compared to bicarbonate and chloride solution. The study shows that a highly reducing environment could be achieved using iron anodes in divided or mixed electrolytes and the pH and redox potential could be optimized using appropriate current and polarity reversal.

  14. 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

  15. 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

  16. Effect of redox conditions on pharmaceutical loss during biological wastewater treatment using sequencing batch reactors.

    PubMed

    Stadler, Lauren B; Su, Lijuan; Moline, Christopher J; Ernstoff, Alexi S; Aga, Diana S; Love, Nancy G

    2015-01-23

    We lack a clear understanding of how wastewater treatment plant (WWTP) process parameters, such as redox environment, impact pharmaceutical fate. WWTPs increasingly install more advanced aeration control systems to save energy and achieve better nutrient removal performance. The impact of redox condition, and specifically the use of microaerobic (low dissolved oxygen) treatment, is poorly understood. In this study, the fate of a mixture of pharmaceuticals and several of their transformation products present in the primary effluent of a local WWTP was assessed in sequencing batch reactors operated under different redox conditions: fully aerobic, anoxic/aerobic, and microaerobic (DO concentration ≈0.3mg/L). Among the pharmaceuticals that were tracked during this study (atenolol, trimethoprim, sulfamethoxazole, desvenlafaxine, venlafaxine, and phenytoin), overall loss varied between them and between redox environments. Losses of atenolol and trimethoprim were highest in the aerobic reactor; sulfamethoxazole loss was highest in the microaerobic reactors; and phenytoin was recalcitrant in all reactors. Transformation products of sulfamethoxazole and desvenlafaxine resulted in the reformation of their parent compounds during treatment. The results suggest that transformation products must be accounted for when assessing removal efficiencies and that redox environment influences the degree of pharmaceutical loss.

  17. 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. PMID:26408978

  18. Groundwater redox conditions and conductivity in a contaminant plume from geoelectrical investigations

    NASA Astrophysics Data System (ADS)

    Naudet, V.; Revil, A.; Rizzo, E.; Bottero, J.-Y.; Bégassat, P.

    Accurate mapping of the electrical conductivity and of the redox potential of the groundwater is important in delineating the shape of a contaminant plume. A map of redox potential in an aquifer is indicative of biodegradation of organic matter and of concentrations of redox-active components; a map of electrical conductivity provides information on the mineralisation of the groundwater. Both maps can be used to optimise the position of pumping wells for remediation. The self-potential method (SP) and electrical resistivity tomography (ERT) have been applied to the contaminant plume associated with the Entressen landfill in south-east France. The self-potential depends on groundwater flow (electrokinetic contribution) and redox conditions ("electro-redox" contribution). Using the variation of the piezometric head in the aquifer, the electrokinetic contribution is removed from the SP signals. A good linear correlation (R2=0.85) is obtained between the residual SP data and the redox potential values measured in monitoring wells. This relationship is used to draw a redox potential map of the overall contaminated site. The electrical conductivity of the subsoil is obtained from 3D-ERT analysis. A good linear correlation (R2=0.91) is observed between the electrical conductivity of the aquifer determined from the 3D-ERT image and the conductivity of the groundwater measured in boreholes. This indicates that the formation factor is nearly homogeneous in the shallow aquifer at the scale of the ERT. From this correlation, a map of the pore water conductivity of the aquifer is obtained.

  19. Iron-mediated Oxidation Induces Conformational Changes within the Redox-sensing Protein HbpS*

    PubMed Central

    de Orué Lucana, Darío Ortiz; Roscher, Mareike; Honigmann, Alf; Schwarz, Julia

    2010-01-01

    HbpS is an extracellular oligomeric protein, which has been shown to act in concert with the two-component system SenS-SenR during the sensing of redox stress. HbpS can bind and degrade heme under oxidative stress conditions, leading to a free iron ion. The liberated iron is subsequently coordinated on the protein surface. Furthermore, HbpS has been shown to modulate the phosphorylation state of the sensor kinase SenS as, in the absence of oxidative stress conditions, HbpS inhibits SenS autophosphorylation whereas the presence of heme or iron ions and redox-stressing agents enhances it. Using HbpS wild type and mutants as well as different biochemical and biophysical approaches, we show that iron-mediated oxidative stress induces both secondary structure and overall intrinsic conformational changes within HbpS. We demonstrate in addition that HbpS is oxidatively modified, leading to the generation of highly reactive carbonyl groups and tyrosine-tyrosine bonds. Further examination of the crystal structure and subsequent mutational analyses allowed the identification of the tyrosine residue participating in dityrosine formation, which occurs between two monomers within the octomeric assembly. Therefore, it is proposed that oxidative modifications causing structural and conformational changes are responsible for the control of SenS and hence of the HbpS-SenS-SenR signaling cascade. PMID:20571030

  20. Physical and functional sensitivity of zinc finger transcription factors to redox change.

    PubMed Central

    Wu, X; Bishopric, N H; Discher, D J; Murphy, B J; Webster, K A

    1996-01-01

    Redox regulation of DNA-binding proteins through the reversible oxidation of key cysteine sulfhydryl groups has been demonstrated to occur in vitro for a range of transcription factors. The direct redox regulation of DNA binding has not been described in vivo, possibly because most protein thiol groups are strongly buffered against oxidation by the highly reduced intracellular environment mediated by glutathione, thioredoxin, and associated pathways. For this reason, only accessible protein thiol groups with high thiol-disulfide oxidation potentials are likely to be responsive to intracellular redox changes. In this article, we demonstrate that zinc finger DNA-binding proteins, in particular members of the Sp-1 family, appear to contain such redox-sensitive -SH groups. These proteins displayed a higher sensitivity to redox regulation than other redox-responsive factors both in vitro and in vivo. This effect was reflected in the hyperoxidative repression of transcription from promoters with essential Sp-1 binding sites, including the simian virus 40 early region, glycolytic enzyme, and dihydrofolate reductase genes. Promoter analyses implicated the Sp-1 sites in this repression. Non-Sp-1-dependent redox-regulated genes including metallothionein and heme oxygenase were induced by the same hyperoxic stress. The studies demonstrate that cellular redox changes can directly regulate gene expression in vivo by determining the level of occupancy of strategically positioned GC-binding sites. PMID:8622648

  1. Comparison of redox and gene expression changes during vegetative/generative transition in the crowns and leaves of chromosome 5A substitution lines of wheat under low-temperature condition.

    PubMed

    Boldizsár, Ákos; Carrera, Dániel Á; Gulyás, Zsolt; Vashegyi, Ildikó; Novák, Aliz; Kalapos, Balázs; Pál, Magda; Galiba, Gábor; Kocsy, Gábor

    2016-02-01

    The aim of our experiments was to investigate the effect of chromosome 5A on the thiol-dependent redox environment and on the transcription of cold- and vernalization-related genes during the vegetative/generative transition in crowns and leaves of wheat. Chinese Spring, a moderately freezing-tolerant variety, and its more and less tolerant substitution lines - [CS(Ch5A)] and [CS(Tsp5A)], respectively - with different combinations of vernalization alleles were compared. At low temperature, the amount of cystine and glutathione disulphide and the related redox potentials increased in the crowns but not in the leaves. In the crowns of the substitution lines, the concentration and redox state of thiols were different only at the vegetative and double ridge (start of the generative transition) stages. The expression of the vernalization-related VRN1 gene increased significantly during the transition both in the crowns and leaves. The transcription of the freezing tolerance-related CBF14, COR14b and COR39 genes markedly increased in both organs after 2 weeks at 4 °C when the seedlings were still in the vegetative stage. This increment was greater in CS(Ch5A) than in CS(Tsp5A). The Ch5A chromosome in CS genetic background enhanced the expression of CBF regulon even in the generative phase in crown that is the key organ for overwintering and freezing tolerance. At certain developmental stages, both the thiol and the transcript levels differed significantly in the two substitution lines.

  2. 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. PMID:15607183

  3. Enhanced PCE dechlorination by biobarrier systems under different redox conditions.

    PubMed

    Kao, C M; Chen, Y L; Chen, S C; Yeh, T Y; Wu, W S

    2003-12-01

    The industrial solvent tetrachloroethylene (PCE) is among the most ubiquitous chlorinated compounds found in groundwater contamination. The objective of this study was to evaluate the (1) feasibility of enhancing PCE biodegradation using cane molasses and sludge cakes as the primary substrates under methanogenic and iron reducing conditions, and (2) potential of installation a sludge cake/cane molasses biobarrier to clean up PCE-contaminated aquifers. The biodegradability of sludge cake (from secondary wastewater treatment system) and cane molasses was tested using bioavailability experiments. Results show that biodegradable materials were released from sludge cake/cane molasses and utilized by microbial consortia. Based on the chemical oxygen demand (COD) tests, approximately 28 and 248 mg of biodegradable COD can be released from 1g of sludge cake and 1g of cane molasses under anaerobic conditions, which have the potential to convert 70 and 620 mg of PCE to ethylene (ETH), respectively. Reductive dechlorination was evaluated using microcosms containing primary substrates (sludge cake/cane molasses) and inocula (aquifer sediments). Results indicate that sludge cake and cane molasses can serve as the diffusion sources of primary substrates, and enhance the reductive dechlorination of PCE under methanogenic processes. However, results from this study were not sufficient enough to show that reductive dechlorination of PCE would occur under iron-reducing conditions. This indicates that more studies need to be performed to further evaluate the role of iron reduction on the PCE dechlorination. Results reveal that it is feasible and applicable to install a sludge cake or cane molasses biobarrier to clean up PCE contaminated aquifers. From an engineering point of view, the sludge cake/cane molasses biobarrier has the potential to become an environmentally and economically acceptable technology for PCE bioremediation.

  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. 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.

  6. 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

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

    PubMed

    Birkner, Nancy; Navrotsky, Alexandra

    2014-04-29

    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.

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

    PubMed

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

    2014-11-15

    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(Mn(4+),Mn(2+))8O16), or sulfate). For each condition, the role of phosphate was studied by repeated additions for up to 290days. 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. PMID:24795042

  9. 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.

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

    PubMed

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

    2014-11-15

    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(Mn(4+),Mn(2+))8O16), or sulfate). For each condition, the role of phosphate was studied by repeated additions for up to 290days. 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.

  11. 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.

  12. Genetic backgrounds and redox conditions influence morphological characteristics and cell differentiation of osteoclasts in mice.

    PubMed

    Narahara, Shun; Matsushima, Haruna; Sakai, Eiko; Fukuma, Yutaka; Nishishita, Kazuhisa; Okamoto, Kuniaki; Tsukuba, Takayuki

    2012-04-01

    Osteoclasts (OCLs) are multinucleated giant cells and are formed by the fusion of mononuclear progenitors of monocyte/macrophage lineage. It is known that macrophages derived from different genetic backgrounds exhibit quite distinct characteristics of immune responses. However, it is unknown whether OCLs from different genetic backgrounds show distinct characteristics. In this study, we showed that bone-marrow macrophages (BMMs) derived from C57BL/6, BALB/c and ddY mice exhibited considerably distinct morphological characteristics and cell differentiation into OCLs. The differentiation of BMMs into OCLs was comparatively quicker in the C57BL/6 and ddY mice, while that of BALB/c mice was rather slow. Morphologically, ddY OCLs showed a giant cell with a round shape, C57BL/6 OCLs were of a moderate size with many protrusions and BALB/c OCLs had the smallest size with fewer nuclei. The intracellular signaling of differentiation and expression levels of marker proteins of OCLs were different in the respective strains. Treatment of BMMs from the three different strains with the reducing agent N-acetylcysteine (NAC) or with the oxidation agent hydrogen peroxide (H(2)O(2)) induced changes in the shape and sizes of the cells and caused distinct patterns of cell differentiation and survival. Thus, genetic backgrounds and redox conditions regulate the morphological characteristics and cell differentiation of OCLs.

  13. Effects of redox conditions on the mineral form of uranium in hydrothermal deposits

    SciTech Connect

    Zavarzin, A.V.

    1981-09-01

    Mineral formation at a hydrothermal uranium deposit almost always occurs in several stages. The minerals produced in the uranium-ore stage are usually localized in aureoles of altered rocks along fault lines produced in the preceding stage. The minerals of the ore stage are also exposed to later solutions, which are often not in equilibrium with the minerals. As a result, the uranium minerals partly dissolve and new mineral species are produced. Data on the composition, formation sequence, and location of the various parageneses of uranium minerals sometimes make it possible to judge the chemistry of the process, particularly the variations in redox conditions. In this paper, the mineral form of uranium is related to the redox conditions of deposition for mineral associations in three ore fields. (JMT)

  14. 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.

  15. 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.

  16. Glutamate-induced metabolic changes influence the cytoplasmic redox state of hippocampal neurons.

    PubMed

    Porras, Omar H; Stutzin, Andrés

    2011-07-22

    Brain cell metabolism is intimately associated with intracellular oxidation-reduction (redox) balance. Glutamatergic transmission is accompanied with changes in substrate preference in neurons. Therefore, we studied cytoplasmatic redox changes in hippocampal neurons in culture exposed to glutamate. Neurons were transfected with HyPer, a genetically encoded redox biosensor for hydrogen peroxide which allows real-time imaging of the redox state. The rate of fluorescence decay, corresponding to the reduction of the biosensor was found to be augmented by low doses of glutamate (10 μM) as well as by pharmacological stimulation of NMDA glutamate receptors. Acute chelation of extracellular Ca(2+) abolished the glutamate-induced effect observed on HyPer fluorescence. Additional experiments indicated that mitochondrial function and hence energetic substrate availability commands the redox state of neurons and is required for the glutamate effect observed on the biosensor signal. Furthermore, our results implicated astrocytic metabolism in the changes of neuronal redox state observed with glutamate. PMID:21708127

  17. Microbial impacts on the geochemistry evolution in a nuclear waste repository -Laboratory experiment of microbially mediated redox changes-

    NASA Astrophysics Data System (ADS)

    Nagaoka, T.

    2010-12-01

    It is important to investigate geochemical evolution around nuclear waste repositories, because geochemical conditions could affect radionuclide migration. Therefore, a laboratory jar experiment was conducted with subsurface sediments, in order to assess the response of the geochemical and microbial communities toward redox processes. The redox process was induced by exposure to air and discontinuation to sediment suspension, which simulated the process occurring during operation of nuclear waste repositories, i.e., tunnel excavation, transport of waste containers, and final backfilling. During the experiments, redox potential, dissolved oxygen, and pH in the suspension were measured, and the concentrations of dissolved ions concentration (e.g., NO3-, SO42- and organic acid), HCl-extractable iron, and also head space gasses (e.g., CO2, CH4) in the jar were analyzed. Moreover, microbial DNA was extracted from the suspension, and PCR-DGGE analysis was performed to analyze the response of microbial communities toward the geochemical changes. As a results, after discontinuation of air exposure with lactate amendment, redox potentials decreased from ca. +300 mV to -430 m V (vs. Ag/AgCl), and the sequential terminal electron-accepting process (TEAPs) was observed with the reactions of aerobic respiration, nitrate reduction, iron reduction, sulfate reduction, and methanogenesis. The related species of the microbes along with TEAPs, e.g., Pseudomonas sp. for nitrate reduction and Desulfovibrio sp. for sulfate reduction, was also detected. These results indicated that the microbial activities would affect the geochemical changes in nuclear repositories.

  18. TRP Channels as Sensors and Signal Integrators of Redox Status Changes

    PubMed Central

    Takahashi, Nobuaki; Mori, Yasuo

    2011-01-01

    Proteins are capable of sensing the redox status of cells. Cysteine residues, which react with oxidants, reductants, and electrophiles, have been increasingly recognized as the mediators of this redox sensitivity. Cation channels encoded by the transient receptor potential (trp) gene superfamily are characterized by a wide variety of activation triggers that act from outside and inside the cell. Recent studies have revealed that a class of TRP channels is sensitive to changes in redox status and is notably susceptible to modifications of cysteine residues, such as oxidation, electrophilic reaction, and S-nitrosylation of sulfhydryls. In this review, we focus on TRP channels, which directly sense redox status, and discuss the biological significance of cysteine modifications and the consequences of this chemical reaction for physiological responses. PMID:22016736

  19. 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. PMID:25749501

  20. Acute restraint stress induces rapid and prolonged changes in erythrocyte and hippocampal redox status.

    PubMed

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

    2013-11-01

    The onset and consequential changes in reduction-oxidation (redox) status that take place in response to short-term stress have not been well defined. This study utilized erythrocytes and neural tissue from male Wistar rats to demonstrate the rapid redox alterations that occur following an acute restraining stress. Serial blood samples collected from catheterized animals were used to measure prolactin, corticosterone, glucose, general oxidative status, and glutathione/glutathione disulfide ratios. Restraint increased prolactin concentration by approximately 300% at 30 min and rapidly returned to baseline values by 120 min of stress. Baseline blood glucose and corticosterone increased during stress exposure by approximately 25% and 150% respectively. Over the experimental period, the erythrocytic oxidative status of restrained animals increased by approximately 10% per hour which persisted after stress exposure, while changes in the glutathione redox couple were not observed until 120 min following the onset of stress. Application of restraint stress increased hippocampal oxidative status by approximately 17% while no change was observed in the amygdala. It was concluded that while endocrine and metabolic markers of stress rapidly increase and habituate to stress exposure, redox status continues to change following stress in both peripheral and neural tissue. Studies with longer post-restraint times and the inclusion of several brain regions should further elucidate the consequential redox changes induced by acute restraint stress.

  1. Manganese-oxide-coated redox bars as an indicator of reducing conditions in soils.

    PubMed

    Dorau, Kristof; Mansfeldt, Tim

    2015-03-01

    Identification of reducing conditions in soils is of concern not only for pedogenesis but also for nutrient and pollutant dynamics. We manufactured manganese (Mn)-oxide-coated polyvinyl chloride bars and proved their suitability for the identification of reducing soil conditions. Birnessite was synthesized and coated onto white polyvinyl chloride bars. The dark brown coatings were homogenous and durable. As revealed by microcosm devices with adjusted redox potentials (E), under oxidizing conditions (E ∼450 mV at pH 7) there was no Mn-oxide removal. Reductive dissolution of Mn-oxides, which is expressed by the removal of the coatings, started under weakly reducing conditions (E ∼175 mV) and was more intensive under moderately reducing conditions (∼80 mV). According to thermodynamics, the removal of Mn-oxide coatings (225 mm d) exceeded the removal of iron (Fe)-oxide coatings (118 mm d) in soil column experiments. This was confirmed in a soil with a shallow and strongly fluctuating water table where both types of redox bars were inserted. Consequently, it was possible to identify reducing conditions in soils using Mn-oxide-coated bars. We recommend this methodology for short-term monitoring because tri- and tetravalent Mn is the preferred electron acceptor compared with trivalent Fe, and this additionally offers the possibility of distinguishing between weakly and moderately reducing conditions. If dissolved Fe is abundant in soils, the possibility of nonenzymatic reduction of Mn has to be taken into account.

  2. Requirement of ArcA for redox regulation in Escherichia coli under microaerobic but not anaerobic or aerobic conditions.

    PubMed

    Alexeeva, Svetlana; Hellingwerf, Klaas J; Teixeira de Mattos, M Joost

    2003-01-01

    In Escherichia coli, the two-component regulatory ArcAB system functions as a major control system for the regulation of expression of genes encoding enzymes involved in both aerobic and anaerobic catabolic pathways. Previously, we have described the physiological response of wild-type E. coli to changes in oxygen availability through the complete range from anaerobiosis to full aerobiosis (S. Alexeeva, B. de Kort, G. Sawers, K. J. Hellingwerf, and M. J. Teixeira de Mattos, J. Bacteriol. 182:4934-4940, 2000, and S. Alexeeva, K. J. Hellingwerf, and M. J. Teixeira de Mattos, J. Bacteriol. 184:1402-1406, 2002). Here, we address the question of the contribution of the ArcAB-dependent transcriptional regulation to this response. Wild-type E. coli and a mutant lacking the ArcA regulator were grown in glucose-limited chemostat cultures at controlled levels of oxygen availability ranging from full aerobiosis to complete anaerobiosis. A flux analysis of the distribution of catabolic fluxes over parallel pathways was carried out, and the intracellular redox state (as reflected by the NADH/NAD ratio) was monitored for all steady states. Deletion of ArcA neither significantly altered the in vivo activity of the pyruvate dehydrogenase complex and pyruvate formate lyase nor significantly affected catabolism under fully aerobic and fully anaerobic conditions. In contrast, profound effects of the absence of ArcA were seen under conditions of oxygen-restricted growth: increased respiration, an altered electron flux distribution over the cytochrome o- and d-terminal oxidases, and a significant change in the intracellular redox state were observed. Thus, the ArcA regulator was found to exert major control on flux distribution, and it is concluded that the ArcAB system should be considered a microaerobic redox regulator.

  3. 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.

  4. Post-depositional stability of long-chain alkenones under contrasting redox conditions

    NASA Astrophysics Data System (ADS)

    Prahl, F. G.; de Lange, G. J.; Lyle, M.; Sparrow, M. A.

    1989-10-01

    PRYMNESIOPHYTE algae, which include the coccolithophorid species Emiliania huxleyi1, are the recognized biological source of a series of long-chain (C37, c38, 39, unsaturated methyl and ethyl ketones2 widely observed in marine sediments3. Studies of E. huxleyi in culture have demonstrated that these biomarkers are attractive geochemical tools for palaeoceanographic study. No-tably, unsaturation patterns within the alkenone series change regularly with growth temperature 3-5 and the total alkenone abundance in the living plant cell is relatively constant, accounting for 5-10% of the total cellular organic carbon5. If these com-pounds are relatively well-preserved in sediments, profiles of alkenone unsaturation patterns and total alkenone concentration with depth in dated deep-sea cores6-8 provide a temporal record of sea surface temperatures and the productivity of an important group of marine phytoplankton3-5. Here we analyse the long-chain alkenone composition of sediment samples from above and below an oxidation front in an ungraded turbidite layer9 deposited 140 +/-12 kyr BP in the Madeira Abyssal Plain10, to evaluate the post-depositional stability of these biomarkers under contrasting redox conditions. The results demonstrate that >85% of the total amount of these compounds is degraded over ~8 kyr as a consequence of diffusion-controlled oxidation10. Remarkably, such extensive degradative loss has little effect on the unsaturation pattern of the residual biomarker series. Thus, we find that long-chain alkenones provide reliable indicators of sea surface temperature in the ocean. The total abundance of these biomarkers in sediments, however, is controlled not only by prymnesiophyte productivity, but also by their degree of exposure to oxidative degradation in the sedimentary process.

  5. The effect of redox conditions and bioirrigation on nitrogen isotope fractionation in marine sediments

    NASA Astrophysics Data System (ADS)

    Rooze, J.; Meile, C.

    2016-07-01

    Nitrogen isotopic signatures of sources and sinks of fixed nitrogen (N) can be used to constrain marine nitrogen budgets. However, the reported fractionation during benthic N2 production varies substantially. To assess the range and mechanisms responsible for such observations, we conducted a model study to evaluate the extent to which nitrification, denitrification, and anaerobic ammonium oxidation contribute to the isotopic composition of in situ N2 production. Different hydrodynamic regimes were taken into account, ranging from bioirrigation to diffusion-dominated transport. The benthic redox conditions were found to control the N isotope effect, which under reducing conditions is driven by fractionation during nitrification and anaerobic ammonium oxidation and under oxidizing conditions by fractionation during denitrification. Environmental parameters, such as the mineralization rate, the bioirrigation intensity, and chemical composition of the overlying water affect the benthic redox zonation and therefore also the benthic N isotope effect. The N isotope effect of benthic N2 production was computed for a wide range of bioirrigation intensities and mineralization rates, and found to be approximately -3‰ for commonly encountered conditions. This value is similar to previous estimates of the global N isotope effect of benthic N2 production, and further constrains the relative importance of water column vs. benthic N2 production.

  6. Tracking changes in ocean redox during the PETM using stable chromium isotopes

    NASA Astrophysics Data System (ADS)

    Dixon, S. K.; Parkinson, I. J.; Sexton, P.; Fehr, M.; James, R. H.; Peacock, C.

    2012-12-01

    Climate models predict a decline in oceanic dissolved oxygen under global warming conditions and observations suggest the expansion of tropical oxygen minimum zones is already underway1, with concern over the trend for future seawater oxygen levels. Therefore, previous deoxygenation events in the geological record may provide insight into the dynamics of changing oxygen levels in the Earth's oceans. One such event, is the Palaeocene-Eocene Thermal Maximum (PETM) at ~55Ma which represents a period of rapid global warming. Multiple lines of evidence suggest that at least on a local scale, near bottom anoxia occurred during the event2,3 and further understanding of changing redox conditions during this period may provide insight into future sea level oxygenation. To track seawater oxygenation during the PETM, we are utilising stable Cr isotope composition of marine carbonates, a new palaeo-redox proxy, which has shown potential when applied to modern and ancient carbonates 4,5. We present δ53Cr, trace element and REE data of foraminiferal ooze deposits over the PETM interval. Samples were taken from the North East Atlantic DSDP site 401, which preserves an exceptional and complete carbonate sequence over the interval, at a time when ocean acidification lead to massive sea floor carbonate dissolution6. Foraminifera were taken from the 63 - 150μm size fraction and planktic count data indicate that the relative proportions of dominant species do not change significantly over the event7. Systematic changes occur in REEs, Cr concentration and δ53Cr coincident with the onset of the negative δ13C excursion. The Cr concentrations of the carbonates decrease into the event, which suggests the sea level Cr concentration has fallen. We interpret this to reflect falling oxygen concentration in the seawater, leading to a decrease in aqueous Cr (VI) via precipitation of Cr out of the water column in the form of insoluble Cr (III) hydroxide. Additionally, we will demonstrate how

  7. 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

  8. 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.

  9. Topsoil morphology indicates bio-effective redox conditions in Venice salt marshes

    NASA Astrophysics Data System (ADS)

    Lang, Friederike; von der Lippe, Moritz; Schimpel, Susanne; Scozzafava-Jaeger, Tiberio; Straub, Wolfgang

    2010-03-01

    Visual traces of iron reduction and oxidation are linked to the redox status of soils and have been used to characterise the quality of agricultural soils. We tested whether this feature could also be used to explain the spatial pattern of the natural vegetation of tidal habitats. If so, an easy assessment of the effect of rising sea level on tidal ecosystems would be possible. Our study was conducted at the salt marshes of the northern lagoon of Venice, which are strongly threatened by erosion and rising sea level and are part of the world heritage "Venice and its lagoon". We analysed the abundance of plant species at 255 sampling points along a land-sea gradient. In addition, we surveyed the redox morphology (presence/absence of red iron oxide mottles in the greyish topsoil horizons) of the soils and the presence of disturbances. We used indicator species analysis, correlation trees and multivariate regression trees to analyse relations between soil properties and plant species distribution. Plant species with known sensitivity to anaerobic conditions (e.g. Halimione portulacoides) were identified as indicators for oxic soils (showing iron oxide mottles within a greyish soil matrix). Plant species that tolerate a low redox potential (e.g. Spartina maritima) were identified as indicators for anoxic soils (greyish matrix without oxide mottles). Correlation trees and multivariate regression trees indicate the dominant role of the redox morphology of the soils in plant species distribution. In addition, the distance from the mainland and the presence of disturbances were identified as tree-splitting variables. The small-scale variation of oxygen availability plays a key role for the biodiversity of salt marsh ecosystems. Our results suggest that the redox morphology of salt marsh soils indicates the plant availability of oxygen. Thus, the consideration of this indicator may enable an understanding of the heterogeneity of biological processes in oxygen-limited systems

  10. 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.

  11. 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.

  12. Inhibition of the differentiation of human myeloid cell lines by redox changes induced through glutathione depletion.

    PubMed Central

    Esposito, F; Agosti, V; Morrone, G; Morra, F; Cuomo, C; Russo, T; Venuta, S; Cimino, F

    1994-01-01

    We have investigated the effect of redox changes in vivo on the differentiation of two human myeloid cell lines, HL-60 and KG-1. The glutathione-depleting agent diethyl maleate (DEM) prevented the development of differentiated features in response to phorbol esters, including adherence of the cells to plastic surfaces and repression of the myeloperoxidase and CD34 genes. Moreover, DEM abolished phorbol 12-myristate 13-acetate-induced activation of the transcription factors AP-1 and Egr-1, suggesting that inhibition of differentiation may be due, at least in part, to redox modifications of these proteins. Images Figure 1 Figure 2 Figure 3 Figure 4 PMID:7519845

  13. Effect of Redox Conditions on MTBE Biodegradation in Surface-Water Systems

    NASA Astrophysics Data System (ADS)

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

    2002-12-01

    Microbial degradation of methyl t-butyl ether (MTBE) was observed in surface-water-sediment microcosms under anaerobic conditions. However, the efficiency and products of anaerobic MTBE biodegradation were strongly dependent on the predominant redox conditions. In the presence of substantial methanogenic activity, MTBE biodegradation was nominal and involved reduction of MTBE to the toxic product, t-butanol (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. The results of this study indicate that microorganisms inhabiting the bed 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.

  14. Influence of pH and Redox Conditions on Copper Leaching

    SciTech Connect

    Kavanaugh, Rathi; Al-Abed, Souhail R.; Purandare, Jaydeep; Allen, Derrick

    2004-03-31

    The Toxicity Characteristic Leaching Procedure (TCLP) is a regulatory leach test in the RCRA programs. It was developed to determine the leaching potential of landfilled waste in order to assess the hazards associated with the leachates. The test was developed to study concentration of hazardous materials in leachates, under a mismanagement scenario, when they are co-disposed with municipal waste. The test uses leaching of waste at either of two acidic pH values i.e., 2.8 and 4.93. While low pH leachant can extract many metals, some metals soluble at higher pH values are either underestimated or totally unaccounted for. The method also has limitations for application to different waste matrices. The procedure does not take into account the effect of redox conditions on leaching. Leaching studies are, therefore, being conducted to determine the effect of combinations of Eh and pH on the leaching potential of mineral and organic wastes. The goal of this study is to propose alternate methods applicable for a variety of waste matrices. The presentation will discuss the effects of combinations of pH and redox conditions on the leaching behavior of copper from a mineral processing waste.

  15. Diagenetic transformation of dissolved organic nitrogen compounds under contrasting sedimentary redox conditions in the Black Sea.

    PubMed

    Schmidt, Frauke; Koch, Boris P; Elvert, Marcus; Schmidt, Gunnar; Witt, Matthias; Hinrichs, Kai-Uwe

    2011-06-15

    Remineralization of organic matter in reactive marine sediments releases nutrients and dissolved organic matter (DOM) into the ocean. Here we focused on the molecular-level characterization of DOM by high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) in sediment pore waters and bottom waters from contrasting redox regimes in the northern Black Sea with particular emphasis on nitrogen-bearing compounds to derive an improved understanding of the molecular transformations involved in nitrogen release. The number of nitrogen-bearing molecules is generally higher in pore waters than in bottom waters. This suggests intensified degradation of nitrogen-bearing precursor molecules such as proteins in anoxic sediments: No significant difference was observed between sediments deposited under oxic vs anoxic conditions (average O/C ratios of 0.55) suggesting that the different organic matter quality induced by contrasting redox conditions does not impact protein diagenesis in the subseafloor. Compounds in the pore waters were on average larger, less oxygenated, and had a higher number of unsaturations. Applying a mathematical model, we could show that the assemblages of nitrogen-bearing molecular formulas are potential products of proteinaceous material that was transformed by the following reactions: (a) hydrolysis and deamination, both reducing the molecular size and nitrogen content of the products and intermediates; (b) oxidation and hydration of the intermediates; and (c) methylation and dehydration.

  16. 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.

  17. In situ Raman study of redox state changes of mitochondrial cytochromes in a perfused rat heart.

    PubMed

    Brazhe, Nadezda A; Treiman, Marek; Faricelli, Barbara; Vestergaard, Jakob H; Sosnovtseva, Olga

    2013-01-01

    We developed a Raman spectroscopy-based approach for simultaneous study of redox changes in c-and b-type cytochromes and for a semiquantitative estimation of the amount of oxygenated myoglobin in a perfused rat heart. Excitation at 532 nm was used to obtain Raman scattering of the myocardial surface of the isolated heart at normal and hypoxic conditions. Raman spectra of the heart under normal pO2 demonstrate unique peaks attributable to reduced c-and b-type cytochromes and oxymyoglobin (oMb). The cytochrome peaks decreased in intensity upon FCCP treatment, as predicted from uncoupling mitochondrial respiration. Conversely, transient hypoxia causes the reversible increase in the intensity of peaks assigned to cytochromes c and c1, reflecting electron stacking proximal to cytochrome oxidase due to the lack of terminal electron acceptor O2. Intensities of peaks assigned to oxy- and deoxyhemoglobin were used for the semiquantitative estimation of oMb deoxygenation that was found to be of approximately 50[Formula: see text] under hypoxia conditions.

  18. Effect of Oxygen and Redox Potential on Glucose Fermentation in Thermotoga maritima under Controlled Physicochemical Conditions

    PubMed Central

    Lakhal, Raja; Auria, Richard; Davidson, Sylvain; Ollivier, Bernard; Dolla, Alain; Hamdi, Moktar; Combet-Blanc, Yannick

    2010-01-01

    Batch cultures of Thermotoga maritima were performed in a bioreactor equipped with instruments adapted for experiments performed at 80°C to mimic the fluctuating oxidative conditions in the hot ecosystems it inhabits. When grown anaerobically on glucose, T. maritima was shown to significantly decrease the redox potential (Eh) of the culture medium down to about −480 mV, as long as glucose was available. Addition of oxygen into T. maritima cultures during the stationary growth phase led to a drastic reduction in glucose consumption rate. However, although oxygen was toxic, our experiment unambiguously proved that T. maritima was able to consume it during a 12-hour exposure period. Furthermore, a shift in glucose metabolism towards lactate production was observed under oxidative conditions. PMID:21461371

  19. 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

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

    PubMed

    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. PMID:22115096

  1. 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.

  2. Impact of redox conditions on metolachlor and metribuzin degradation in Mississippi flood plain soils.

    PubMed

    Mulbach, C K; Porthouse, J D; Jugsujinda, A; DeLaune, R D; Johnson, A B

    2000-11-01

    The effect of soil redox conditions on the degradation of metolachlor and metribuzin in two Mississippi soils (Forrestdale silty clay loam and Loring silt loam) were examined in the laboratory. Herbicides were added to soil in microcosms and incubated either under oxidized (aerobic) or reduced (anaerobic) conditions. Metolachlor and metribuzin degradation under aerobic condition in the Forrestdale soil proceeded at rates of 8.83 ngd(-1) and 25 ngd(-1), respectively. Anaerobic degradation rates for the two herbicides in the Forestdale soil were 8.44 ngd(-1) and 32.5 ngd(-1), respectively. Degradation rates for the Loring soil under aerobic condition were 24.8 ngd(-1) and 12.0 ngd(-1) for metolachlor and metribuzin, respectively. Metolachlor and metribuzin degradation rates under anaerobic conditions in the Loring soil were 20.9 ngd(-1) and 5.35 ngd(-1). Metribuzin degraded faster (12.0 ngd(-1)) in the Loring soil under aerobic conditions as compared to anaerobic conditions (5.35 ngd(-1)).

  3. Redox-linked conformational changes of a multiheme cytochrome from Geobacter sulfurreducens

    SciTech Connect

    Morgado, Leonor; Bruix, Marta; Londer, Yuri Y.; Pokkuluri, P. Raj; Schiffer, Marianne; Salgueiro, Carlos A. . E-mail: csalgueiro@dq.fct.unl.pt

    2007-08-17

    Multiheme c-type cytochromes from members of the Desulfovibrionacea and Geobactereacea families play crucial roles in the bioenergetics of these microorganisms. Thermodynamic studies using NMR and visible spectroscopic techniques on tetraheme cytochromes c {sub 3} isolated from Desulfovibrio spp. and more recently on a triheme cytochrome from Geobacter sulfurreducens showed that the properties of each redox centre are modulated by the neighbouring redox centres enabling these proteins to perform energy transduction and thus contributing to cellular energy conservation. Electron/proton transfer coupling relies on redox-linked conformational changes that were addressed for some multiheme cytochromes from the comparison of protein structure of fully reduced and fully oxidised forms. In this work, we identify for the first time in a multiheme cytochrome the simultaneous presence of two different conformations in solution. This was achieved by probing the different oxidation stages of a triheme cytochrome isolated from G. sulfurreducens using 2D-NMR techniques. The results presented here will be the foundations to evaluate the modulation of the redox centres properties by conformational changes that occur during the reoxidation of a multiheme protein.

  4. Kinetics and yields of bacteriochlorophyll fluorescence: redox and conformation changes in reaction center of Rhodobacter sphaeroides.

    PubMed

    Maróti, Péter

    2008-09-01

    Induction of the bacteriochlorophyll fluorescence under rectangular shape of intense laser diode illumination (1 W cm(-2), 808 nm) was measured over wide time range from 10 microseconds to 4 s in whole cells, chromatophore and isolated reaction center protein of wild type and carotenoid-less mutant (R-26.1) of purple photosynthetic bacterium Rhodobacter sphaeroides. While the antenna-containing species showed large and positive variable fluorescence (Fv) to initial fluorescence (F0) (Fv/F0 approximately 4.5 in whole cells), the isolated RC had negative change (Fv/F0 approximately -0.6) during photochemistry. In chromatophore from R-26.1, only seven times higher rate was measured than in isolated reaction center under identical experimental conditions. The enhancement effect of large antenna on the rate of photochemistry in chromatophore was partially compensated by the favorable pigment absorption properties in isolated RC. The transition from membrane bound to isolated form of the reaction center was probed by titration of zwitterionic detergent LDAO in chromatophore, and at 0.03% LDAO concentration, sharp change of the variable fluorescence was observed. The sudden drop was explained by the formation of LDAO micelles. After the photochemical phase, additional change of fluorescence yield could be observed in isolated RC considered as manifestation of long-living conformations of the trapped redox states of the protein characterized by non-exponential kinetics. Strong support was provided for use of the fluorescence induction to track structural and conformation changes at their earliest phases in chromatophores and isolated reaction centers.

  5. 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

  6. Glyco-redox, a link between oxidative stress and changes of glycans: Lessons from research on glutathione, reactive oxygen and nitrogen species to glycobiology.

    PubMed

    Taniguchi, Naoyuki; Kizuka, Yasuhiko; Takamatsu, Shinji; Miyoshi, Eiji; Gao, Congxiao; Suzuki, Keiichiro; Kitazume, Shinobu; Ohtsubo, Kazuaki

    2016-04-01

    Reduction-oxidation (redox) response is one of the most important biological phenomena. The concept introduced by Helmut Sies encouraged many researchers to examine oxidative stress under pathophysiological conditions. Our group has been interested in redox regulation under oxidative stress as well as glycobiology in relation to disease. Current studies by our group and other groups indicate that functional and structural changes of glycans are regulated by redox responses resulting from the generation of reactive oxygen species (ROS) or reactive nitrogen species (RNS) in various diseases including cancer, diabetes, neurodegenerative disease such as Parkinson disease, Alzheimer's disease and amyotrophic lateral sclerosis (ALS), and chronic obstructive pulmonary disease (COPD), even though very few investigators appear to be aware of these facts. Here we propose that the field "glyco-redox" will open the door to a more comprehensive understanding of the mechanism associated with diseases in relation to glycan changes under oxidative stress. A tight link between structural and functional changes of glycans and redox system under oxidative stress will lead to the recognition and interest of these aspects by many scientists. Helmut's contribution in this field facilitated our future perspectives in glycobiology.

  7. Role of biotransformation, sorption and mineralization of (14)C-labelled sulfamethoxazole under different redox conditions.

    PubMed

    Alvarino, T; Nastold, P; Suarez, S; Omil, F; Corvini, P F X; Bouju, H

    2016-01-15

    (14)C-sulfamethoxazole biotransformation, sorption and mineralization was studied with heterotrophic and autotrophic biomass under aerobic and anoxic conditions, as well as with anaerobic biomass. The (14)C-radiolabelled residues distribution in the solid, liquid and gas phases was closely monitored along a total incubation time of 190 h. Biotransformation was the main removal mechanism, mineralization and sorption remaining below 5% in all the cases, although the presence of a carbon source exerted a positive effect on the mineralization rate by the aerobic heterotrophic bacteria. In fact, an influence of the type of primary substrate and the redox potential was observed in all cases on the biotransformation and mineralization rates, since an enhancement of the removal rate was observed when an external carbon source was used as a primary substrate under aerobic conditions, while a negligible effect was observed under nitrifying conditions. In the liquid phases collected from all assays, up to three additional peaks corresponding to (14)C-radiolabelled residues were detected. The highest concentration was observed under anaerobic conditions, where two radioactive metabolites were detected representing each around 15% of the total applied radioactivity after 180 h incubation. One of the metabolites detected under anoxic and anaerobic conditions, is probably resulting from ring cleavage of the isoxazole ring. PMID:26546766

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. Assessment of redox changes to hydrogen peroxide-sensitive proteins during EGF signaling.

    PubMed

    Cuddihy, Sarah L; Winterbourn, Christine C; Hampton, Mark B

    2011-07-01

    Hydrogen peroxide acts as a second messenger in growth factor signaling where it can oxidize and modify the function of redox-sensitive proteins. While selective thiol oxidation has been measured, there has been no global assessment of protein oxidation following growth factor activation. Significant changes to the abundant and widely distributed redox sensitive thiol proteins were observed in A431 epidermoid carcinoma cells exposed to hydrogen peroxide, but no changes were observed following treatment with epidermal growth factor (EGF). This included members of the peroxiredoxin family, which were also monitored in the presence of the thioredoxin reductase inhibitor auranofin to limit their capacity to recycle to the reduced form. We conclude that widespread thiol oxidation does not occur in cells during EGF signaling, and that hydrogen peroxide must act in a highly localized or selective manner.

  14. Biodegradation of alpha- and beta-hexachlorocyclohexane in a soil slurry under different redox conditions.

    PubMed Central

    Bachmann, A; Walet, P; Wijnen, P; de Bruin, W; Huntjens, J L; Roelofsen, W; Zehnder, A J

    1988-01-01

    Aerobic conditions proved to be best for the microbiol conversion of alpha-hexachlorocyclohexane (alpha-HCH) in a soil slurry. The dry soil contained 400 mg of alpha-HCH per kg. This xenobiotic compound was mineralized within about 18 days at an initial rate of 23 mg/kg of soil per day by the mixed native microbial population of the soil. The only intermediate that was detected during breakdown was pentachlorocyclohexene, which was detected at very small concentrations. Alpha-HCH was also bioconverted under methanogenic conditions. However, a rather long acclimation period (about 30 days) was necessary before degradation started, at a rate of 13 mg/kg of soil per day. Mass balance calculations showed that about 85% of the initial alpha-HCH that was present was converted to monochlorobenzene, 3,5-dichlorophenol, and a trichlorophenol isomer, possibly 2,4,5-trichlorophenol. Under both denitrifying and sulfate-reducing conditions, no significant bioconversion of alpha-HCH was observed. The beta isomer of HCH was recalcitrant at all of the four redox conditions studied. We propose that the specific spatial chloride arrangement of the beta isomer is responsible for its stability. The results reported here with complex soil slurry systems showed that alpha-HCH is, in contrast to the existing data in the literature, best degraded biologically in the presence of oxygen. PMID:2449868

  15. 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.

  16. Sedimentary Trace Metal-Organic Interactions as Proxies for Oceanic Redox Conditions

    NASA Astrophysics Data System (ADS)

    Cruse, A. M.; Lyons, T. W.; Hannigan, R.

    2007-12-01

    Knowledge of trace-metal partitioning in oceanic sediments (e.g., Fe, Mo, U, Zn) are requisite to the construction of accurate models of geochemical cycling in modern and ancient waters. Factors such as oxygen penetration depth and bottom-water redox; sedimentation rate; and supply of reactants, such as dissolved sulfide, are known to affect metal sequestration in and remobilization from coastal sediments. In addition to these factors, the flux of organic carbon (OC) and the composition of this carbon are also a key in the sequestration of these metals. Currently, however, there is an absence of quantitative information on the mass balance of metals fixed in coastal sediments through direct interactions with OC, how OC remineralization affects this mass balance, and the specific nature of the metal-OC relationship. To address these issues, we have undertaken a field-based study to test the hypothesis that porewater redox conditions are recorded in the concentrations of trace metals bound in the sedimentary OC pool. We have collected sediments from several modern anoxic/euxinic basins: the central Black Sea, the Orca Basin, the Cariaco Basin, and Effingham Inlet (Vancouver Island). These environments vary in terms of dissolved sulfide concentrations and sedimentary iron sulfide geochemistry. Additionally, the sediments are characterized by a range in OC concentrations, and proximity to terrestrial sources. Extractable organic carbon was characterized with gas chromatography, and OC-bound metals are quantified using high-performance liquid chromatography- inductively coupled mass spectrometry. The preliminary results suggest that variations in the ratios of aromatic to saturate hydrocarbons may control the speciation of metals in the organic carbon pool. Bottomwater redox may be one factor controlling this relationship, although it is currently unclear if this is due to variations in metal speciation or the direct involvement of S in the OC-metal reaction mechanism

  17. 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. PMID:25900116

  18. 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.

  19. 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.

  20. 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.

  1. Role of redox homeostasis in thermo-tolerance under a climate change scenario

    PubMed Central

    de Pinto, Maria Concetta; Locato, Vittoria; Paradiso, Annalisa; De Gara, Laura

    2015-01-01

    Background Climate change predictions indicate a progressive increase in average temperatures and an increase in the frequency of heatwaves, which will have a negative impact on crop productivity. Over the last decade, a number of studies have addressed the question of how model plants or specific crops modify their metabolism when exposed to heat stress. Scope This review provides an overview of the redox pathways that contribute to how plants cope with heat stress. The focus is on the role of reactive oxygen species (ROS), redox metabolites and enzymes in the signalling pathways leading to the activation of defence responses. Additional attention is paid to the regulating mechanisms that lead to an increase in specific ROS-scavenging systems during heat stress, which have been studied in different model systems. Finally, increasing thermo-tolerance in model and crop plants by exposing them to heat acclimation or to exogenous treatments is discussed. Conclusions Although there is clear evidence that several strategies are specifically activated according to the intensity and the duration of heat stress, as well as the capacity of the different species or genotypes to overcome stress, an alteration in redox homeostasis seems to be a common event. Different mechanisms that act to enhance redox systems enable crops to overcome heat stress more effectively. Knowledge of thermo-tolerance within agronomic biodiversity is thus of key importance to enable researchers to identify new strategies for overcoming the impacts of climate change, and for decision-makers in planning for an uncertain future with new choices and options open to them. PMID:26034009

  2. Effects of temperature and redox conditions on degradation of chlorinated phenols in freshwater sediments

    SciTech Connect

    Rogers, J.E.; Kohring, G.W.; Wiegel, J.

    1988-11-01

    The effect of temperature and redox conditions on the anaerobic degradation of 2,4-dichlorophenol (2,4-DCP) was investigated in anaerobic sediment slurries, prepared from local freshwater pond sediments. Under methanogenic conditions, 2,4-DCP dechlorination occurred in the temperature range between 5 and 50 C. Although dechlorination was not observed above 50 C, anaerobic bacterial activity was indicated by methane formation up to 60 C. In sediment samples from two sites and at all temperatures from 5 to 50 C, 2,4-DCP was transformed to 4-chlorophenol (4-CP). The 4-CP intermediate was subsequently degraded after an extended lag period. Adaptation periods for 2,4-DCP transformation decreased between 5 and 25 C, were essentially constant between 25 and 35 C, and increased between 35 and 40 C. Degradation rates increased exponentially between 15 and 30 C, had a second peak at 35 C, and decreased to about 5% of the peak activity by 40 C. In one sediment sample, an increase in degradation rates was observed following the minimum at 40 C, suggesting that at least two different organisms were involved in the 2,4-DCP dechlorination. Storage of the original sediment slurries for 2 months at 12 C resulted in increased adaptation times but did not affect the degradation rates.

  3. 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.

  4. 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.

  5. Spatio-temporal changes in glutathione and thioredoxin redox couples during ionizing radiation-induced oxidative stress regulate tumor radio-resistance.

    PubMed

    Patwardhan, R S; Sharma, D; Checker, R; Thoh, M; Sandur, S K

    2015-10-01

    Ionizing radiation (IR)-induced oxidative stress in tumor cells is effectively managed by constitutive and inducible antioxidant defense systems. This study was initiated to understand the relative contribution of different redox regulatory systems in determining the tumor radio-resistance. In this study, human T-cell lymphoma (Jurkat) cells were exposed to IR (4 Gy) and monitored for the spatio-temporal changes in cellular redox regulatory parameters. We monitored the changes in the levels of reactive oxygen species (ROS) (total, mitochondrial, primary, and secondary), thiols (total, surface, and intracellular), GSH/GSSG ratio, antioxidant enzyme activity viz. thioredoxin (Trx), Trx reductase (TrxR), glutathione peroxidase, and glutathione reductase with respect to time. We have also measured protein glutathionylation. We observed that tumor cells mount a biphasic response after IR exposure which can be divided into early (0-6 h) and late (16-48 h) responses in terms of changes in cellular redox parameters. During early response, constitutively active GSH and Trx systems respond to restore cellular redox balance to pre-exposure levels and help in activation of redox-sensitive transcription factor Nrf-2. During late response, increase in the levels of antioxidants GSH and Trx rescue cells against IR-mediated damage. We observed that disruption of either glutathione or thioredoxin metabolism led to partial impairment of ability of cells to survive against IR-induced damage. But simultaneous disruption of both the pathways significantly increased radio sensitivity of Jurkat cells. This highlighted the importance of these two antioxidant pathways in regulating redox homeostasis under conditions of IR-induced oxidative stress. PMID:26021764

  6. Spatio-temporal changes in glutathione and thioredoxin redox couples during ionizing radiation-induced oxidative stress regulate tumor radio-resistance.

    PubMed

    Patwardhan, R S; Sharma, D; Checker, R; Thoh, M; Sandur, S K

    2015-10-01

    Ionizing radiation (IR)-induced oxidative stress in tumor cells is effectively managed by constitutive and inducible antioxidant defense systems. This study was initiated to understand the relative contribution of different redox regulatory systems in determining the tumor radio-resistance. In this study, human T-cell lymphoma (Jurkat) cells were exposed to IR (4 Gy) and monitored for the spatio-temporal changes in cellular redox regulatory parameters. We monitored the changes in the levels of reactive oxygen species (ROS) (total, mitochondrial, primary, and secondary), thiols (total, surface, and intracellular), GSH/GSSG ratio, antioxidant enzyme activity viz. thioredoxin (Trx), Trx reductase (TrxR), glutathione peroxidase, and glutathione reductase with respect to time. We have also measured protein glutathionylation. We observed that tumor cells mount a biphasic response after IR exposure which can be divided into early (0-6 h) and late (16-48 h) responses in terms of changes in cellular redox parameters. During early response, constitutively active GSH and Trx systems respond to restore cellular redox balance to pre-exposure levels and help in activation of redox-sensitive transcription factor Nrf-2. During late response, increase in the levels of antioxidants GSH and Trx rescue cells against IR-mediated damage. We observed that disruption of either glutathione or thioredoxin metabolism led to partial impairment of ability of cells to survive against IR-induced damage. But simultaneous disruption of both the pathways significantly increased radio sensitivity of Jurkat cells. This highlighted the importance of these two antioxidant pathways in regulating redox homeostasis under conditions of IR-induced oxidative stress.

  7. Characterizing Redox Conditions in Oxygen-deficient Waters Off Peru During the 2013 US GEOTRACES Zonal Transect

    NASA Astrophysics Data System (ADS)

    Cutter, G. A.; Nielsdottir, M.

    2014-12-01

    The oxygen-deficient zone that extends from coastal Peru well into the tropical Pacific Ocean has been described as "suboxic," but recent measurements of sulfate reduction suggest it may have some anoxic characteristics (e.g., free sulfide). The redox poise of suboxia strongly affects the solubility/stability of a wide variety of trace elements and therefore their vertical and horizontal transport. The problem is that suboxic is not chemically well defined, but certainly represents a very wide range of redox conditions (pE of ca. 10 to -2). During the 2013 US GEOTRACES Pacific cruise (International GEOTRACES section GP16) we determined a suite of redox couples to help define the redox poise in the water column: oxygen(/water), iodate/iodide, nitrate/nitrite, selenate/elemental Se, arsenate/arsenite, and sulfate/hydrogen sulfide. Using the RV Thomas Thompson we occupied a total of 11 stations along 12° S from coastal Peru to 94° W to sample the oxygen deficient waters using a conventional CTD/rosette and the trace metal-clean US GEOTRACES CTD/carousel. Determinations of all the redox tracers were made on board ship except for selenium. On the Peru shelf, oxygen concentrations were less than 10 μM from 30m to the bottom, while farther offshore the depth of this oxygen minimum was 700 m thick starting at ca. 80 m depth; the layer thickness steadily decreased moving west. In spite of the low oxygen conditions, nitrate and iodate were still detectable, while their corresponding reduced species had maxima in the low O2 waters. Dissolved hydrogen sulfide was below the detection limit of 70 pM, and no evidence of As(V) reduction was found; selenium speciation has yet to be determined. The lack of detectable dissolved hydrogen sulfide shows the redox conditions are certainly not anoxic, and incomplete iodate and nitrate reduction suggest the redox environment is more oxidizing than previously reported. The apparent temporal and spatial variability of the redox poise will

  8. [Effect of sulfur on the species of Fe and As under redox condition in paddy soil].

    PubMed

    Tang, Bing-Pei; Yang, Shi-Jie; Wang, Dai-Zhang; Rao, Wei; Zhang, Ya-Nan; Wang, Dan; Zhu, Yun-Ji

    2014-10-01

    Redox conditions of the polluted paddy soil with exogenous As were simulated by redox reaction apparatus after flowing N2 and O2 applied with different forms of inorganic sulfur(CK-S0, elemental sulfur-S1 and sulfate-S2). Results showed that redox potential (Eh) was about -100 - -200 mV and the pH 7.0-8.0 and the pe + pH 4-7 in soil solution when flowed N2, and Eh about 200 mV and the pH 6.5-7.5 and pe + pH 9-12 when continuously flowed O2. Concentrations of the dissolved Fe in soil solution were in 1.2-1.6 mg x L(-1) either flowed N2 or O2, and the order of Fe concentrations was AsS0 treatment > AsS1 treatment > AsS2 treatment. Amounts of soil Fe oxide by HCl extraction from different treatments were 5 g · kg(-1) lower than the original soil [(21.4 ± 0.3) g · kg(-1)] when flowed N2, and it was in favor of the transformation of crystal Fe into amorphous iron and Fe2+. Activity of Fe oxides from different treatments increased comparing to that of the original soil (46. 8%), and the order of activity of Fe oxides was AsS2 treatment (49.4%) < AsS1 treatment (60%). Fe2+ in solution and FeS were oxidized into Fe3+, and hydrolysis of Fe3+ was produced into Fe(OH)3 precipitation when flowed O2. It increased the contents of acid-soluble and crystal Fe oxide, and the order of activity of Fe oxides was AsS1 (41.2%) treatment > AsS2 (36.1%) treatment. Concentrations of As in soil solution were in the order of AsS0 [(1.13 ± 0.04) mg · L(-1)] > AsS1 [(0.89 ± 0.01) mg L(- 1)] > AsS2 [ (0.77 ± 0.04 )mg · L(-1)] when flowed N2 and was AsS1 [(0.77 ± 0.01) mg · L(-1)] > AsS0 [(0.20 ± 0.09 ) mg · L(-1)] > AsS2 [(0.09 ± 0.01) mg · L(-1)] when flowed O2. The proportions of arsenic fractions followed the order of the residual phases (34.9%-41.4%) ≈ specifically-sorbed (37.4%-39.5%) > well-crystallized hydrous oxides of Fe/Mn (23.3%-25.6%) > non-specifically sorbed (2.4%-3.3%) > amorphous hydrous oxides of Fe/Mn (0.5%-0.8%) when flowed N2, and was the residual phases (30

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

    PubMed

    Seifi-Skishahr, Farnaz; Damirchi, Arsalan; Farjaminezhad, Manoochehr; Babaei, Parvin

    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

  10. 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

  11. 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. PMID:27285534

  12. 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.

  13. Characterizing redox conditions and monitoring attenuation of selected pharmaceuticals during artificial recharge through a reactive layer.

    PubMed

    Valhondo, Cristina; Carrera, Jesús; Ayora, Carlos; Tubau, Isabel; Martinez-Landa, Lurdes; Nödler, Karsten; Licha, Tobias

    2015-04-15

    A permeable reactive layer was installed at the floor of an infiltration basin. The reactive layer comprised 1) vegetable compost to provide a sorption surface for neutral organic compounds and to release easily degradable organic matter, thus generating a sequence of redox states, and 2) minor amounts of clay and iron oxide to increase sorption of cationic and anionic species, respectively. Field application of this design was successful in generating denitrification, and manganese-, and iron-reducing conditions beneath the basin. This, together with the increase in types of sorption sites, may explain the improved removal of three of the four selected pharmaceuticals compared with their behavior prior to installation of the layer. After installation of the reactive layer, atenolol concentrations were below the detection limits in the vadose zone. Moreover, concentrations of gemfibrozil and cetirizine were reduced to 20% and 40% of their initial concentrations, respectively, after 200 h of residence time. In contrast, prior to installation of the reactive layer, the concentrations of these three pharmaceuticals in both the vadose zone and the aquifer were more than 60% of the initial concentration. Carbamazepine exhibited recalcitrant behavior both prior to and after the reactive barrier installation. PMID:25625636

  14. Characterizing redox conditions and monitoring attenuation of selected pharmaceuticals during artificial recharge through a reactive layer.

    PubMed

    Valhondo, Cristina; Carrera, Jesús; Ayora, Carlos; Tubau, Isabel; Martinez-Landa, Lurdes; Nödler, Karsten; Licha, Tobias

    2015-04-15

    A permeable reactive layer was installed at the floor of an infiltration basin. The reactive layer comprised 1) vegetable compost to provide a sorption surface for neutral organic compounds and to release easily degradable organic matter, thus generating a sequence of redox states, and 2) minor amounts of clay and iron oxide to increase sorption of cationic and anionic species, respectively. Field application of this design was successful in generating denitrification, and manganese-, and iron-reducing conditions beneath the basin. This, together with the increase in types of sorption sites, may explain the improved removal of three of the four selected pharmaceuticals compared with their behavior prior to installation of the layer. After installation of the reactive layer, atenolol concentrations were below the detection limits in the vadose zone. Moreover, concentrations of gemfibrozil and cetirizine were reduced to 20% and 40% of their initial concentrations, respectively, after 200 h of residence time. In contrast, prior to installation of the reactive layer, the concentrations of these three pharmaceuticals in both the vadose zone and the aquifer were more than 60% of the initial concentration. Carbamazepine exhibited recalcitrant behavior both prior to and after the reactive barrier installation.

  15. 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

  16. Verbal Conditioning and Therapeutic Change

    ERIC Educational Resources Information Center

    Lapuc, Paul S.; Harmatz, Morton G.

    1970-01-01

    Investigates the generalization of verbal conditioning effects to postconditioning personality and behavioral measures. Results demonstrated conditioning and generalization to some of the personality measures. (Author)

  17. Redox-dependent structure change and hyperfine nuclear magnetic resonance shifts in cytochrome c

    SciTech Connect

    Feng, Yiquing; Roder, H.; Englander, S.W. )

    1990-04-10

    Proton nuclear magnetic resonance assignments for reduced and oxidized equine cytochrome c show that many individual protons exhibit different chemical shifts in the two protein forms, reflecting diamagnetic shift effects due to structure change, and in addition contact and pseudocontact shifts that occur only in the paramagnetic oxidized form. To evaluate the chemical shift differences for structure change, the authors removed the pseudocontact shift contribution by a calculation based on knowledge of the electron spin g tensor. The g-tensor calculation, when repeated using only 12 available C{sub {alpha}}H proton resonances for cytochrom c from tuna, proved to be remarkably stable. The derived g tensor was then used together with spatial coordinates for the oxidized form to calculate the pseudocontact shift contribution to proton resonances at 400 identifiable sites throughout the protein, so that the redox-dependent chemical shift discrepancy, could be evaluated. Large residual changes in chemical shift define the Fermi contact shifts, where are found as expected to be limited to the immediate covalent structure of the heme and its ligands and to be asymmetrically distributed over the heme. The chemical shift discrepancies observed appear in the main to reflect structure-dependent diamagnetic shifts rather than hyperfine effects due to displacements in the pseudocontact shift field. Although 51 protons in 29 different residues exhibit significant chemical shift changes, the general impressions one of small structural adjustments to redox-dependent strain rather than sizeable structural displacements or rearrangements.

  18. Assessing the regulation of leaf redox status under water stress conditions in Arabidopsis thaliana: Col-0 ecotype (wild-type and vtc-2), expressing mitochondrial and cytosolic roGFP1.

    PubMed

    Brossa, Ricard; Pintó-Marijuan, Marta; Jiang, Keni; Alegre, Leonor; Feldman, Lewis J

    2013-07-01

    Using Arabidopsis plants Col-0 and vtc2 transformed with a redox sensitive green fluorescent protein, (c-roGFP) and (m-roGFP), we investigated the effects of a progressive water stress and re-watering on the redox status of the cytosol and the mitochondria. Our results establish that water stress affects redox status differently in these two compartments, depending on phenotype and leaf age, furthermore we conclude that ascorbate plays a pivotal role in mediating redox status homeostasis and that Col-0 Arabidopsis subjected to water stress increase the synthesis of ascorbate suggesting that ascorbate may play a role in buffering changes in redox status in the mitochondria and the cytosol, with the presumed buffering capacity of ascorbate being more noticeable in young compared with mature leaves. Re-watering of water-stressed plants was paralleled by a return of both the redox status and ascorbate to the levels of well-watered plants. In contrast to the effects of water stress on ascorbate levels, there were no significant changes in the levels of glutathione, thereby suggesting that the regeneration and increase in ascorbate in water-stressed plants may occur by other processes in addition to the regeneration of ascorbate via the glutathione. Under water stress in vtc2 lines it was observed stronger differences in redox status in relation to leaf age, than due to water stress conditions compared with Col-0 plants. In the vtc2 an increase in DHA was observed in water-stressed plants. Furthermore, this work confirms the accuracy and sensitivity of the roGFP1 biosensor as a reporter for variations in water stress-associated changes in redox potentials.

  19. Predicting Redox Conditions in Groundwater Using Statistical Techniques: Implications for Nitrate Transport in Groundwater and Streams

    NASA Astrophysics Data System (ADS)

    Tesoriero, A. J.; Terziotti, S.

    2014-12-01

    Nitrate trends in streams often do not match expectations based on recent nitrogen source loadings to the land surface. Groundwater discharge with long travel times has been suggested as the likely cause for these observations. The fate of nitrate in groundwater depends to a large extent on the occurrence of denitrification along flow paths. Because denitrification in groundwater is inhibited when dissolved oxygen (DO) concentrations are high, defining the oxic-suboxic interface has been critical in determining pathways for nitrate transport in groundwater and to streams at the local scale. Predicting redox conditions on a regional scale is complicated by the spatial variability of reaction rates. In this study, logistic regression and boosted classification tree analysis were used to predict the probability of oxic water in groundwater in the Chesapeake Bay watershed. The probability of oxic water (DO > 2 mg/L) was predicted by relating DO concentrations in over 3,000 groundwater samples to indicators of residence time and/or electron donor availability. Variables that describe position in the flow system (e.g., depth to top of the open interval), soil drainage and surficial geology were the most important predictors of oxic water. Logistic regression and boosted classification tree analysis correctly predicted the presence or absence of oxic conditions in over 75 % of the samples in both training and validation data sets. Predictions of the percentages of oxic wells in deciles of risk were very accurate (r2>0.9) in both the training and validation data sets. Depth to the bottom of the oxic layer was predicted and is being used to estimate the effect that groundwater denitrification has on stream nitrate concentrations and the time lag between the application of nitrogen at the land surface and its effect on streams.

  20. 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.

  1. 48 CFR 52.243-5 - Changes and Changed Conditions.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 48 Federal Acquisition Regulations System 2 2010-10-01 2010-10-01 false Changes and Changed....243-5 Changes and Changed Conditions. As prescribed in 43.205(e), insert the following clause: Changes and Changed Conditions (APR 1984) (a) The Contracting Officer may, in writing, order changes in...

  2. 48 CFR 52.243-5 - Changes and Changed Conditions.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 48 Federal Acquisition Regulations System 2 2011-10-01 2011-10-01 false Changes and Changed....243-5 Changes and Changed Conditions. As prescribed in 43.205(e), insert the following clause: Changes and Changed Conditions (APR 1984) (a) The Contracting Officer may, in writing, order changes in...

  3. 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)

  4. Integrating Techniques to Understand the Biological Controls on Redox Conditions at Water Table Interfaces in the Subsurface

    NASA Astrophysics Data System (ADS)

    Voytek, M. A.; Cozzarelli, I. M.; Kirshtein, J. D.; Bohlke, J.

    2006-05-01

    The Norman Oklahoma Landfill is a closed, unlined municipal landfill in the alluvium of the Canadian River with a leachate plume that extends at least 225m downgradient. The fate and transport of chemical species in the subsurface of this system is largely controlled by changes in the reduction-oxidation (redox) potential which are driven by hydrology, chemistry and microbiology. In this study, we focused on the microbiological and geochemical factors that control redox conditions at the mixing interface of recharge water and aquifer/plume water at two sites (a background site where the contaminant plume rarely reaches the water table and a contaminated site where the plume routinely mixes with recharge water). We examined denitrification, nitrification, iron reduction, sulfate reduction, and methanogenesis using standard microbiological, molecular and geochemical approaches to quantify these processes. Multilevel wells were sampled for geochemistry and core material was collected at the same locations for microbial analyses. The distribution and abundance of specific microbial guilds were determined using Most Probable Number (MPN) analysis and quantitative PCR (qPCR). In general, we see evidence of enhanced microbial activity (i.e. microbially mediated chemical transformations) and microbial abundance at the interfaces due to the increase in oxidized electron acceptors as well as dissolved organic carbon availability from the landfill leachate. For example, water ammonia concentrations decrease near the water table possibly due to nitrification, when ammonium rich leachate water comes into contact with oxygenated recharge. The oxidation of ammonium by nitrification to nitrate is supported by the observation of an increase in nitrogen isotope fractionation resulting in increasing delta-15N values which also correspond to an increase in the abundance of nitrifying bacteria. Based on profiles of the geochemistry and abundance and distribution of specific microbial

  5. Investigating the impacts of deep ocean euxinia on continental shelf environments during the Great Ordovician Biodiversification Event: did changes in global oceanic redox have any effect?

    NASA Astrophysics Data System (ADS)

    Marenco, P. J.; Marenco, K. N.; Phillips, D. E.; Garcia, E.; Toure, N.; Fullem, A.

    2013-12-01

    The Great Ordovician Biodiversification Event was one of the most important radiations in the history of animal life. In particular, the GOBE was characterized by pronounced increases in diversity within the Paleozoic and Modern Evolutionary Faunas (e.g., Droser and Finnegan, 2003). Rather than being attributable to a singular cause, a number of tectonic, ecologic, and climate-related factors are thought to have contributed to this biodiversification event (e.g., Servais et al., 2009). For example, continental shelf area during the GOBE was more extensive than at any other time during the Phanerozoic, and the availability of these warm, shallow-water, well-oxygenated environments likely influenced the radiation (e.g., Servais et al., 2009). Despite this evidence for favorable conditions, recent geochemical studies suggest that the early Paleozoic, including the Ordovician, was a time of episodic deep ocean euxinia (e.g., Gill et al., 2011, Thompson and Kah, 2012). It remains unclear how the hypothesized deep ocean euxinia may have affected the GOBE. For example, it is possible that episodic incursions of euxinic deep water onto the continental shelves may have acted to slow down the GOBE or even dampen its magnitude. On the other hand, such incursions may have accelerated the radiation by adding additional selection pressures to communities that were already adapting to new predation and substrate conditions. Alternatively, the GOBE may have proceeded without any incursions of euxinic deep water onto the continental shelves. One way to address this issue is to investigate short-term, localized redox changes in shallow marine settings. Here we present results from our ongoing investigation of redox changes in shallow-water environments from the Lower and Middle Ordovician of Utah. Specifically, we use abundances of total organic carbon (TOC) and total sulfur (TS) as localized redox proxies. We use the isotopic composition of carbonate associated sulfate (δ34SCAS

  6. Interaction between plastid and mitochondrial retrograde signalling pathways during changes to plastid redox status

    PubMed Central

    Blanco, Nicolás E.; Guinea-Díaz, Manuel; Whelan, James; Strand, Åsa

    2014-01-01

    Mitochondria and chloroplasts depend upon each other; photosynthesis provides substrates for mitochondrial respiration and mitochondrial metabolism is essential for sustaining photosynthetic carbon assimilation. In addition, mitochondrial respiration protects photosynthesis against photoinhibition by dissipating excess redox equivalents from the chloroplasts. Genetic defects in mitochondrial function result in an excessive reduction and energization of the chloroplast. Thus, it is clear that the activities of mitochondria and plastids need to be coordinated, but the manner by which the organelles communicate to coordinate their activities is unknown. The regulator of alternative oxidase (rao1) mutant was isolated as a mutant unable to induce AOX1a expression in response to the inhibitor of the mitochondrial cytochrome c reductase (complex III), antimycin A. RAO1 encodes the nuclear localized cyclin-dependent kinase E1 (CDKE1). Interestingly, the rao1 mutant demonstrates a genome uncoupled phenotype also in response to redox changes in the photosynthetic electron transport chain. Thus, CDKE1 was shown to regulate both LIGHT HARVESTING COMPLEX B (LHCB) and ALTERNATIVE OXIDASE 1 (AOX1a) expression in response to retrograde signals. Our results suggest that CDKE1 is a central nuclear component integrating mitochondrial and plastid retrograde signals and plays a role in regulating energy metabolism during the response to stress. PMID:24591717

  7. [Changes in redox potentials during transitional processes in pure and mixed cultures of Escherichia coli and Serratia marcescens].

    PubMed

    Oktiabr'skiĭ, O N; Zelenin, E N; Smirnova, G V

    1984-01-01

    There were studied transitional processes accompanying the beginning of growth under glucose addition and stopping of growth under glucose exhaustion in pure and mixed aerobic cultures of Escherichia coli and Serratia marcescens. Continued record of Eh, pH, and CO2 showed that these processes sharply differ from each other in their character in pure and mixed cultures, it is particularly related to the changes of the redox potential. There is no characteristic change in the redox potential in pure culture of E. coli at growth termination in the case when S. marcescens cells are present in the culture.

  8. Solubility and speciation of S in hydrous magmas: Effects of composition and redox conditions at 1050°C and 200 MPa

    NASA Astrophysics Data System (ADS)

    Botcharnikov, R. E.; Wilke, M.; Jugo, P. J.; Holtz, F.

    2009-12-01

    Knowledge on the behaviour of sulphur in natural magmas provides important constraints on geochemical and geophysical processes occurring in magmatic and hydrothermal systems. The partitioning of S between silicate melts and coexisting fluids is mainly controlled by the transformations of S species into sulphide or sulphate form due to changes in the redox conditions of the system. The saturation of a silicate melt in respect of sulphide- or/and sulphate-bearing phase is responsible for the maximum concentrations of dissolved sulphur. Hence, the composition of the silicate melt and activities of melt components, especially Fe and Ca, are critical parameters controlling S partitioning. Here, we present experimental data on the solubility of S in rhyolitic to basaltic magmas equilibrated with aqueous S-bearing fluids of constant bulk composition (5 wt.% H2O and 1 wt.% S in the system) at 1050°C, 200 MPa and redox conditions corresponding to that of logfO2~QFM-2 to QFM+3 (where QFM is quartz-fayalite-magnetite oxygen buffer). For studied melt compositions, the solubility of S systematically increases with increasing fO2 and depolymerisation of the silicate melt. At logfO2 < ~QFM, S solubility is controlled by the stability of FeS phase while at logfO2 > ~QFM+2, CaSO4 is a stable phase. Both S-bearing phases may coexist at intermediate fO2 values. The largest difference in solubilities of sulphide and sulphate S is observed for basaltic melts, where the concentration of sulphide S is 0.07 wt.%, being approximately ten times lower than the concentration of sulphate S of about 0.6 wt.%. Other melt compositions show lower concentration differences between dissolved S species, having, however, similar positive dependence on fO2. Thus, the partition coefficients of S between fluid and silicate melt vary as a function of melt composition and redox conditions. The largest partition coefficients (>1000) are determined for reduced silicic melts. For all investigated melt

  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 Code

    PubMed Central

    Jones, Dean P.

    2015-01-01

    Abstract Significance: The redox code is a set of principles that defines the positioning of the nicotinamide adenine dinucleotide (NAD, NADP) and thiol/disulfide and other redox systems as well as the thiol redox proteome in space and time in biological systems. The code is richly elaborated in an oxygen-dependent life, where activation/deactivation cycles involving O2 and H2O2 contribute to spatiotemporal organization for differentiation, development, and adaptation to the environment. Disruption of this organizational structure during oxidative stress represents a fundamental mechanism in system failure and disease. Recent Advances: Methodology in assessing components of the redox code under physiological conditions has progressed, permitting insight into spatiotemporal organization and allowing for identification of redox partners in redox proteomics and redox metabolomics. Critical Issues: Complexity of redox networks and redox regulation is being revealed step by step, yet much still needs to be learned. Future Directions: Detailed knowledge of the molecular patterns generated from the principles of the redox code under defined physiological or pathological conditions in cells and organs will contribute to understanding the redox component in health and disease. Ultimately, there will be a scientific basis to a modern redox medicine. Antioxid. Redox Signal. 23, 734–746. PMID:25891126

  11. 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

  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. 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.

  14. 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.

  15. 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.

  16. Changes in Sedimentary Redox Associated with Mussel (Mytilus edulis L.) Farms on the West-Coast of Scotland

    PubMed Central

    Wilding, Thomas A.

    2012-01-01

    Aquaculture is growing rapidly in response to an increasing demand for protein and the over-exploitation of wild fisheries. Mussel (family Mytilidae) production has doubled over the last decade and currently stands at 1.5 million tonnes production per annum. Mussels produce organic biodeposits which are dispersed around the production site and, potentially, impact the receiving environment in a number of inter-linked ways. The reported benthic impacts that occur, primarily through the accumulation of these biodeposits and associated organic enrichment, vary widely between studies. The objectives of this research were to determine the nature of the relationship between sediment redox (a proxy for oxygenation) and farm-proximity and covariables whilst accounting for, and quantifying, differences in redox between sites. Sediment cores (N = 159) were taken remotely around a random sample of mussel farms, redox was measured at 10 mm sediment depth and linked to farm-distance and sediment organic/shell content and particle size, using an additive, mixed, weighted regression model. Redox varied considerably between sites and there was a highly significant reduction (50 mV) in redox adjacent to the mussel lines. Redox increased non-linearly with distance, rising rapidly at >7 m from the farm edge. The modest reduction in sediment oxygenation in close proximity to mussel farms reported here suggests that farms located over sediments characterised by pre-existing oxygen stress are likely to exacerbate benthic species impoverishment associated with reducing sedimentary conditions whilst those located over highly oxygenated sediments are likely to increase benthic productivity. PMID:23028817

  17. 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.

  18. The effects of water radiolysis on local redox conditions in the Oklo, Gabon, natural fission reactors 10 and 16

    NASA Astrophysics Data System (ADS)

    Savary, Véronique; Pagel, Maurice

    1997-11-01

    In an underground nuclear waste repository, the chemical behavior of some stored fission products and actinides depends on the redox conditions during their long-term evolution. In this respect, radiolysis is an important phenomenon which can significantly modify the local redox conditions. The Oklo natural fission zones are good examples where the effect of radiolysis can be deduced from a mineralogical and geochemical study. Zones 10 and 16 were studied because they are located at depth of 270 m in an area devoid of any recent water circulation and not subject to the effect of the lateritic alteration occurring elsewhere in this area. In zone 10, there is a marked evolution of the UPbFeS mineralogy from the center to the periphery of the reactor zone. In the center, uraninite shows silicification and coffinitisation with the formation of galena and native lead; the PbO content of uraninite can be as much as 20 wt%. In the periphery of the reactor zone, some radiogenic lead is present as minium (Pb 30 4) and in Pb-bearing calcite. In the surrounding sandstones, hematite is widespread. In zone 16, the mineral paragenesis is generally comparable with that of zone 10 but with some differences. Galena is the only Pb-bearing mineral associated with uraninite crystals. The PbO content of uraninite is always <7 wt%. In the periphery of the alteration zone, barite partly replaces quartz. In the reactor zone, hematite is sometimes replaced by pyrite. In an area where the fission zone 10 is in contact with sandstones devoid of organic matter, H 2OH 2O 2 and H 20H 2 ± CH 4 inclusions were observed in healed microcracks in the detrital quartz grains. Based on microthermometric measurements, the salinity of the aqueous solution ranges from 0.2 to 18 wt% eq. NaCl. Raman analysis of the gas phase indicates that the hydrogen to oxygen ratio differs from an inclusion to the other. The presence of H 2- and O 2-bearing fluid inclusions confirms the existence of water

  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. 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.

  3. Records of radionuclide deposition in two salt marshes in the United Kingdom with contrasting redox and accumulation conditions

    NASA Astrophysics Data System (ADS)

    Thomson, J.; Dyer, F. M.; Croudace, I. W.

    2002-03-01

    Single cores from two salt marshes in the United Kingdom located near different nuclear facilities were investigated to compare chronostratigraphic estimates derived from the natural radionuclide 210Pb excess with estimates from the known times of introduction of artificial radionuclides to the environment. Both cores selected had clear visual indications of redox zonation, and evidence for diagenetic redox perturbation of the radionuclide records was also sought. In the core from Beaulieu Marsh on the south coast of England, the redox zonation was revealed by the profiles of the redox-sensitive elements Mn + I, Fe + P + As, and S, and the records of nuclear discharges were entirely contained within oxidized conditions in the upper 40 cm. The constant flux/constant sedimentation 210Pb excess accumulation estimate was 76% of that derived from the 1963 fallout 137Cs level (0.35 vs. 0.46 g cm -2 yr -1 dry mass), but the constant flux 210Pb excess method indicated that accumulation rates were lower at Beaulieu before ˜1950. On any timescale, 137Cs appears earlier in the sediment record than its introduction to the environment, but although downward diffusion of 137Cs relative to 241Am has clearly occurred, the 137Cs peak still appeared in place and there was negligible penetration of 137Cs into underlying reduced conditions. This core also contained a peak of the 60Co discharges from either or both the Winfrith and La Hague nuclear plants that peaked in 1980 and 1984, respectively. The sediments in the core from Wyre Marsh on the eastern coast of the Irish Sea had accumulated more rapidly than those at Beaulieu, and in this case the redox zonation could be established only from Mn and S profiles. Here, the constant initial activity 210Pb excess accumulation rate estimate was 125% of that derived from the 137Cs peak correlated with the 1975 Sellafield discharge maximum (0.79 vs. 0.64 g cm -2 yr -1). Sellafield discharge 137Cs swamps fallout or Chernobyl 137Cs signals

  4. 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...

  5. 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.

  6. 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. PMID:24383760

  7. 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...

  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. Flavin Redox Switching of Protein Functions

    PubMed Central

    Zhu, Weidong; Moxley, Michael A.

    2011-01-01

    Abstract Flavin cofactors impart remarkable catalytic diversity to enzymes, enabling them to participate in a broad array of biological processes. The properties of flavins also provide proteins with a versatile redox sensor that can be utilized for converting physiological signals such as cellular metabolism, light, and redox status into a unique functional output. The control of protein functions by the flavin redox state is important for transcriptional regulation, cell signaling pathways, and environmental adaptation. A significant number of proteins that have flavin redox switches are found in the Per-Arnt-Sim (PAS) domain family and include flavoproteins that act as photosensors and respond to changes in cellular redox conditions. Biochemical and structural studies of PAS domain flavoproteins have revealed key insights into how flavin redox changes are propagated to the surface of the protein and translated into a new functional output such as the binding of a target protein in a signaling pathway. Mechanistic details of proteins unrelated to the PAS domain are also emerging and provide novel examples of how the flavin redox state governs protein–membrane interactions in response to appropriate stimuli. Analysis of different flavin switch proteins reveals shared mechanistic themes for the regulation of protein structure and function by flavins. Antioxid. Redox Signal. 14, 1079–1091. PMID:21028987

  10. Proxies for Redox Conditions during early Aptian Ocean Anoxic Event 1a

    NASA Astrophysics Data System (ADS)

    Brassell, S. C.

    2012-04-01

    addition, the elevated Mo concentrations (7 - 540 ppm) in these sediments are typical of euxinic conditions, and yet marcasite, a likely product of pyrite oxidation, is prevalent throughout the section. Comparison of these proxies reveals a correspondence between the lycopane index and Mo concentrations, with higher values for both parameters during warmer intervals. These results suggest that specific indicators for levels of oxygenation may perhaps be controlled by environmental variables including changes in ocean temperatures that exert an influence on surface ocean conditions that govern seasonal productivity and affect stratification in the water column, and yet are independent from the controls on anoxia within the sediment after deposition.

  11. 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.

  12. 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. PMID:26788013

  13. Regulation of gap junction channels and hemichannels by phosphorylation and redox changes: a revision.

    PubMed

    Pogoda, Kristin; Kameritsch, Petra; Retamal, Mauricio A; Vega, José L

    2016-01-01

    Post-translational modifications of connexins play an important role in the regulation of gap junction and hemichannel permeability. The prerequisite for the formation of functional gap junction channels is the assembly of connexin proteins into hemichannels and their insertion into the membrane. Hemichannels can affect cellular processes by enabling the passage of signaling molecules between the intracellular and extracellular space. For the intercellular communication hemichannels from one cell have to dock to its counterparts on the opposing membrane of an adjacent cell to allow the transmission of signals via gap junctions from one cell to the other. The controlled opening of hemichannels and gating properties of complete gap junctions can be regulated via post-translational modifications of connexins. Not only channel gating, but also connexin trafficking and assembly into hemichannels can be affected by post-translational changes. Recent investigations have shown that connexins can be modified by phosphorylation/dephosphorylation, redox-related changes including effects of nitric oxide (NO), hydrogen sulfide (H2S) or carbon monoxide (CO), acetylation, methylation or ubiquitination. Most of the connexin isoforms are known to be phosphorylated, e.g. Cx43, one of the most studied connexin at all, has 21 reported phosphorylation sites. In this review, we provide an overview about the current knowledge and relevant research of responsible kinases, connexin phosphorylation sites and reported effects on gap junction and hemichannel regulation. Regarding the effects of oxidants we discuss the role of NO in different cell types and tissues and recent studies about modifications of connexins by CO and H2S.

  14. Redox Imbalance in Lung Cancer of Patients with Underlying Chronic Respiratory Conditions

    PubMed Central

    Mateu-Jiménez, Mercè; Sánchez-Font, Albert; Rodríguez-Fuster, Alberto; Aguiló, Rafael; Pijuan, Lara; Fermoselle, Clara; Gea, Joaquim; Curull, Víctor; Barreiro, Esther

    2016-01-01

    Chronic respiratory diseases such as obstructive pulmonary disease (COPD) and oxidative stress may underlie lung cancer (LC). We hypothesized that the profile of oxidative and antioxidant events may differ in lung tumors and blood compartments of patients with non-small cell LC (NSCLC) with and without COPD. Redox markers (immunoblotting, ELISA, chemiluminescence, 2D electrophoresis and proteomics) were analyzed in blood samples of 17 control subjects and 80 LC patients (59 LC-COPD and 21 LC) and lung specimens (tumor and nontumor) from those undergoing thoracotomy (35 patients: 23 LC-COPD and 12 LC). As smoking history was more prevalent in LC-COPD patients, these were further analyzed post hoc as heavy and moderate smokers (cutoff, 60 pack-years). Malondialdehyde (MDA)–protein adducts and SOD1 levels were higher in tumor and nontumor samples of LC-COPD than in LC. In tumors compared with nontumors, SOD2 protein content was greater, whereas catalase levels were decreased in both LC and LC-COPD patients. Blood superoxide anion levels, protein carbonylation and nitration were greater in LC and LC-COPD patients than in the controls, and in the latter patients compared with the former. Systemic superoxide anion, protein carbonyls and nitrotyrosine above specific cutoff values best identified underlying COPD among all patients. Smoking did not influence the study results. A differential expression profile of oxidative stress markers exists in blood and, to a lesser extent, in the tumors of LC-COPD patients. These findings suggest that systemic oxidative stress and lung antioxidants (potential biomarkers) may predispose patients with chronic respiratory diseases to a higher risk for LC. PMID:26772773

  15. 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.

  16. 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.

  17. Monitoring Changes in the Redox State of Myoglobin in Cardiomyocytes by Raman Spectroscopy Enables the Protective Effect of NO Donors to Be Evaluated.

    PubMed

    Almohammedi, Abdullah; Kapetanaki, Sofia M; Hudson, Andrew J; Storey, Nina M

    2015-10-20

    Raman microspectroscopy has been used to monitor changes in the redox and ligand-coordination states of the heme complex in myoglobin during the preconditioning of ex vivo cardiomyocytes with pharmacological drugs that release nitric oxide (NO). These chemical agents are known to confer protection on heart tissue against ischemia-reperfusion injury. Subsequent changes in the redox and ligand-coordination states during experimental simulations of ischemia and reperfusion have also been monitored. We found that these measurements, in real time, could be used to evaluate the preconditioning treatment of cardiomyocytes and to predict the likelihood of cell survival following a potentially lethal period of ischemia. Evaluation of the preconditioning treatment was done at the single-cell level. The binding of NO to myoglobin, giving a 6-coordinate ferrous-heme complex, was inferred from the measured Raman bands of a cardiomyocyte by comparison to pure solution of the protein in the presence of NO. A key change in the Raman spectrum was observed after perfusion of the NO-donor was completed, where, if the preconditioning treatment was successful, the bands corresponding to the nitrosyl complex were replaced by bands corresponding to metmyoglobin, Mb(III). An observation of Mb(III) bands in the Raman spectrum was made for all of the cardiomyocytes that recovered contractile function, whereas the absence of Mb(III) bands always indicated that the cardiomyocyte would be unable to recover contractile function following the simulated conditions of ischemia and reperfusion in these experiments.

  18. Changes in glutathione-dependent redox status and mitochondrial energetic strategies are part of the adaptive response during the filamentation process in Candida albicans.

    PubMed

    Hala, Guedouari; Rachel, Gergondey; Arthur, Bourdais; Océane, Vanparis; Anne-Laure, Bulteau; Jean-Michel, Camadro; Françoise, Auchère

    2014-10-01

    Candia albicans is an opportunist pathogen responsible for a large spectrum of infections, from superficial mycosis to systemic diseases called candidiasis. Its ability to grow in various morphological forms, such as unicellular budding yeast, filamentous pseudohyphae and hyphae, contributes to its survival in the diverse microenvironments it encounters in the host. During infection in vivo, C. albicans is faced with high levels of ROS generated by phagocytes, and the thiol-dependent redox status of the cells reflects their levels of oxidative stress. We investigated the role of glutathione during the transition between the yeast and hyphal forms of the pathogen, in relation to possible changes in mitochondrial bioenergetic pathways. Using various growth media and selective mutations affecting the filamentation process, we showed that C. albicans filamentation was always associated with a depletion of intracellular glutathione levels. Moreover, the induction of hypha formation resulted in general changes in thiol metabolism, including the oxidation of cell surface -SH groups and glutathione excretion. Metabolic adaptation involved TCA cycle activation, acceleration of mitochondrial respiration and a redistribution of electron transfer pathways, with an increase in the contribution of the alternative oxidase and rotenone-insensitive dehydrogenase. Changes in redox status and apparent oxidative stress may be necessary to the shift to adaptive metabolic pathways, ensuring normal mitochondrial function and ATP levels. The consumption of intracellular glutathione levels during the filamentation process may thus be the price paid by C. albicans for survival in the conditions encountered in the host.

  19. Changes in glutathione-dependent redox status and mitochondrial energetic strategies are part of the adaptive response during the filamentation process in Candida albicans.

    PubMed

    Guedouari, H; Gergondey, R; Bourdais, A; Vanparis, O; Bulteau, A L; Camadro, J M; Auchère, F

    2014-09-01

    Candida albicans is an opportunist pathogen responsible for a large spectrum of infections, from superficial mycosis to systemic diseases called candidiasis. Its ability to grow in various morphological forms, such as unicellular budding yeast, filamentous pseudohyphae and hyphae, contributes to its survival in the diverse microenvironments it encounters in the host. During infection in vivo, C. albicans is faced with high levels of reactive oxygen species (ROS) generated by phagocytes, and the thiol-dependent redox status of the cells reflects their levels of oxidative stress. We investigated the role of glutathione during the transition between the yeast and hyphal forms of the pathogen, in relation to possible changes in mitochondrial bioenergetic pathways. Using various growth media and selective mutations affecting the filamentation process, we showed that C. albicans filamentation was always associated with a depletion of intracellular glutathione levels. Moreover, the induction of hypha formation resulted in general changes in thiol metabolism, including the oxidation of cell surface -SH groups and glutathione excretion. Metabolic adaptation involved tricarboxylic acid (TCA) cycle activation, acceleration of mitochondrial respiration and a redistribution of electron transfer pathways, with an increase in the contribution of the alternative oxidase and rotenone-insensitive dehydrogenase. Changes in redox status and apparent oxidative stress may be necessary to the shift to adaptive metabolic pathways, ensuring normal mitochondrial function and adenosine triphosphate (ATP) levels. The consumption of intracellular glutathione levels during the filamentation process may thus be the price paid by C. albicans for survival in the conditions encountered in the host.

  20. 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. PMID:9580389

  1. 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.

  2. 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

  3. 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…

  4. 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...

  5. Thiol switches in redox regulation of chloroplasts: balancing redox state, metabolism and oxidative stress.

    PubMed

    Dietz, Karl-Josef; Hell, Rüdiger

    2015-05-01

    In photosynthesizing chloroplasts, rapidly changing energy input, intermediate generation of strong reductants as well as oxidants and multiple participating physicochemical processes and pathways, call for efficient regulation. Coupling redox information to protein function via thiol modifications offers a powerful mechanism to activate, down-regulate and coordinate interdependent processes. Efficient thiol switching of target proteins involves the thiol-disulfide redox regulatory network, which is highly elaborated in chloroplasts. This review addresses the features of this network. Its conditional function depends on specificity of reduction and oxidation reactions and pathways, thiol redox buffering, but also formation of heterogeneous milieus by microdomains, metabolite gradients and macromolecular assemblies. One major player is glutathione. Its synthesis and function is under feedback redox control. The number of thiol-controlled processes and involved thiol switched proteins is steadily increasing, e.g., in tetrapyrrole biosynthesis, plastid transcription and plastid translation. Thus chloroplasts utilize an intricate and versatile redox regulatory network for intraorganellar and retrograde communication.

  6. 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.

  7. 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.

  8. Pore-scale analysis of effects of electrode morphology and electrolyte flow conditions on performance of vanadium redox flow batteries

    NASA Astrophysics Data System (ADS)

    Qiu, Gang; Dennison, C. R.; Knehr, K. W.; Kumbur, E. C.; Sun, Ying

    2012-12-01

    A 3D pore-scale transport resolved model is used to study the performance characteristics of a vanadium redox flow battery (VRFB) with various electrode morphologies under different operating conditions. Three electrode structures are reconstructed from X-ray computed tomography (XCT) images of porous carbon felt electrode materials. The local vanadium concentration, overpotential, current density and overall cell voltage for the positive half cell are examined. The results indicate that the cell voltage increases with increasing electrolyte flow rate due to decreasing concentration gradients of vanadium species within the porous electrode. However, the marginal gain in cell voltage diminishes once the concentration field approaches uniformity under convection-dominated mass transport conditions at sufficiently high electrolyte flow rates. The model also predicts that electrode structures with low porosity (high surface area) result in more uniform and lower absolute current density and overpotential fields at the expense of increased pressure drop. Finally, poor cell performance is observed for simulations operated at low electrolyte flow rates and low states of charge due to the fuel starvation (i.e., insufficient amount of reactant in the cell).

  9. Redox change during magma ascent; Observation from three volcanoes and implication for gas monitoring

    NASA Astrophysics Data System (ADS)

    Moussallam, Yves; Oppenheimer, Clive; Schipper, Ian C.; Hartley, Magaret; Scaillet, Bruno; Gaillard, Fabrice; Peters, Nial; Kyle, Phil

    2015-04-01

    The oxidation state of volcanic gases dictates their speciation and hence their reactivity in the atmosphere. It has become increasingly recognized that the oxidation state of a magma can be strongly affected by degassing. The oxidation state of gases will equally be impacted and the composition of gases emitted by volcanoes will therefore be function of the magma degassing history. This presentation will show results from three volcanoes where the oxidation state of the magma has been tracked during degassing. At Erebus and Laki we used Fe X-ray absorption near-edge structure spectroscopy (XANES) on extensive suites of melt inclusions and glasses, while at Surtsey we used S-Kα peak shifts measurements by electron microprobe (EPMA) on melt inclusions, embayment and glasses. At all three locations we found that a strong reduction of both Fe and S is associated with magma ascent. At Erebus this reduction is greatest, corresponding to a fall in magmatic fO2 of more than two log units. We propose that sulfur degassing can explain the observed evolution of the redox state with ascent and show that forward modeling using initial melt composition can successfully predict the composition of the gas phase measured at the surface. We suggest that the redox state of volcanic gases (expressed in term of redox couples: H2O/H2, SO2/H2S and CO2/CO) can be used to monitor the depth of gas-melt segregation at active volcanoes.

  10. 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.

  11. 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

  12. Redox-induced changes in flavin structure and roles of flavin N(5) and the ribityl 2'-OH group in regulating PutA--membrane binding.

    PubMed

    Zhang, Weimin; Zhang, Min; Zhu, Weidong; Zhou, Yuzhen; Wanduragala, Srimevan; Rewinkel, Dustin; Tanner, John J; Becker, Donald F

    2007-01-16

    PutA is a novel flavoprotein in Escherichia coli that switches from a transcriptional repressor to a membrane-bound proline catabolic enzyme. Previous crystallographic studies of the PutA proline dehydrogenase (PRODH) domain under oxidizing conditions revealed that FAD N(5) and the ribityl 2'-OH group form hydrogen bonds with Arg431 and Arg556, respectively. Here we identify molecular interactions in the PutA PRODH active site that underlie redox-dependent functional switching of PutA. We report that reduction of the PRODH domain induces major structural changes in the FAD cofactor, including a 22 degrees bend of the isoalloxazine ring along the N(5)-N(10) axis, crankshaft rotation of the upper part of the ribityl chain, and formation of a new hydrogen bond network involving the ribityl 2'-OH group, FAD N(1), and Gly435. The roles of the FAD 2'-OH group and the FAD N(5)-Arg431 hydrogen bond pair in regulating redox-dependent PutA-membrane associations were tested using FAD analogues and site-directed mutagenesis. Kinetic membrane binding measurements and cell-based reporter gene assays of modified PutA proteins show that disrupting the FAD N(5)-Arg431 interaction impairs the reductive activation of PutA-membrane binding. We also show that the FAD 2'-OH group acts as a redox-sensitive toggle switch that controls PutA-membrane binding. These results illustrate a new versatility of the ribityl chain in flavoprotein mechanisms. PMID:17209558

  13. 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

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

    PubMed Central

    Hiller, Kenly A.; Foreman, Kenneth H.; Weisman, David

    2015-01-01

    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. PMID:26231655

  15. 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.

  16. 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

  17. 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

  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 PAGESBeta

    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 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

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

    2012-02-01

    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.

  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. 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.

  4. Redox-Dependent Conformational Changes in Cytochrome c Oxidase Suggest a Gating Mechanism for Proton Uptake

    SciTech Connect

    Qin, Ling; Liu, Jian; Mills, Denise A.; Proshlyakov, Denis A.; Hiser, Carrie; Ferguson-Miller, Shelagh

    2009-08-05

    A role for conformational change in the coupling mechanism of cytochrome c oxidase is the subject of controversy. Relatively small conformational changes have been reported in comparisons of reduced and oxidized crystal structures of bovine oxidase but none in bacterial oxidases. Comparing the X-ray crystal structures of the reduced (at 2.15 {angstrom} resolution) and oxidized forms of cytochrome c oxidase from Rhodobacter sphaeroides, we observe a displacement of heme a3 involving both the porphyrin ring and the hydroxyl farnesyl tail, accompanied by protein movements in nearby regions, including the mid part of helix VIII of subunit I which harbors key residues of the K proton uptake path, K362 and T359. The conformational changes in the reduced form are reversible upon reoxidation. They result in an opening of the top of the K pathway and more ordered waters being resolved in that region, suggesting an access path for protons into the active site. In all high-resolution structures of oxidized R. sphaeroides cytochrome c oxidase, a water molecule is observed in the hydrophobic region above the top of the D path, strategically positioned to facilitate the connection of residue E286 of subunit I to the active site or to the proton pumping exit path. In the reduced and reduced plus cyanide structures, this water molecule disappears, implying disruption of proton conduction from the D path under conditions when the K path is open, thus providing a mechanism for alternating access to the active site.

  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. 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

  7. Accumulation of manganese superoxide dismutase under metal-depleted conditions: proposed role for zinc ions in cellular redox balance.

    PubMed Central

    Otsu, Kaoru; Ikeda, Yoshitaka; Fujii, Junichi

    2004-01-01

    A diet low in copper results in increased levels of MnSOD (manganese superoxide dismutase), a critical antioxidative enzyme conferring protection against oxidative stress, in rat liver mitochondria. The mechanism for this was investigated using cultured HepG2 cells, a human hepatocellular carcinoma-derived line. MnSOD activity increased 5-7-fold during incubation in a medium supplemented with metal-depleted fetal bovine serum, with a corresponding elevation of its mRNA levels. Metal depletion also decreased CuZnSOD and glutathione peroxidase levels to approx. 70-80% of baseline. When zinc ions were added to the medium at micromolar levels, MnSOD accumulation was suppressed; however, copper ions had essentially no effect on MnSOD expression. Since the intracellular redox status was shifted to a more oxidized state by metal depletion, we examined the DNA-binding activity of NF-kappaB (nuclear factor-kappaB), an oxidative stress-sensitive transactivating factor that plays a primary role in MnSOD induction. A gel shift assay indicated that the DNA-binding activity of NF-kappaB was increased in cells maintained in metal-depleted culture, suggesting the involvement of the transactivating function of NF-kappaB in this induction. This was further supported by the observation that curcumin suppressed both the DNA-binding activity of NF-kappaB and the induction of MnSOD mRNA in cells cultivated under metal-depleted conditions. These results suggest that the level of zinc, rather than copper, is a critical regulatory factor in MnSOD expression. It is possible that a deficiency of zinc in the low-copper diet may be primarily involved in MnSOD induction. PMID:14531733

  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. 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

  10. Conformational Changes in the Novel Redox Sensor Protein HbpS Studied by Site-Directed Spin Labeling and Its Turnover in Dependence on the Catalase-Peroxidase CpeB

    PubMed Central

    Klare, Johann P.

    2012-01-01

    Abstract Aims: To establish conditions to study the oligomeric assembly of heme-binding protein (HbpS) in solution by applying the tools of site-directed spin labeling combined with pulse electron paramagnetic resonance (SDSL EPR) spectroscopy, as well as to analyze redox stress-based conformational changes in HbpS subunits within the oligomer in solution. In vivo elucidation of molecular mechanisms that control the downregulation of the novel redox-system HbpS-SenS-SenR. Results: Using a set of specifically generated HbpS mutants, and SDSL EPR spectroscopy, we show the octomeric assembly of HbpS in solution, and demonstrate that iron-mediated stress induces conformational changes in HbpS subunits within the octamer. We further demonstrate that the catalase-peroxidase CpeB protects HbpS from hydrogen peroxide (H2O2)-mediated oxidative attack in vivo. Moreover, chromosomal inactivation of cpeB results in an enhanced sensitivity of the mutant to redox-cycling compounds. Innovation: SDSL EPR has been used in this work for the first time to monitor redox-mediated conformational changes in a redox-sensing protein in solution. This work substantially explains redox-dependent dynamics in HbpS at the atomic level, and presents novel molecular mechanisms supporting downregulation of a signaling cascade. Conclusion: Iron-mediated stress induces movements of subunits within the HbpS octomeric assembly. We suggest a motion of the C-terminal α-helix toward the preceding helical segment. These events upregulate the activity of the HbpS-SenS-SenR system, in which HbpS acts as an accessory element. The mycelia-associated CpeB, under the control of HbpS-SenS-SenR, protects the extracellular HbpS from oxidation in vivo. Thus, de novo synthesized HbpS proteins downregulate the HbpS-SenS-SenR signaling cascade. Antioxid. Redox Signal. 16, 639–648. PMID:21846213

  11. Clostridium thermocellum DSM 1313 transcriptional responses to redox perturbation

    DOE PAGESBeta

    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.

  12. Genetically encoded reactive oxygen species (ROS) and redox indicators.

    PubMed

    Pouvreau, Sandrine

    2014-02-01

    Redox processes are increasingly being recognized as key elements in the regulation of cellular signaling cascades. They are frequently encountered at the frontier between physiological functions and pathological events. The biological relevance of intracellular redox changes depends on the subcellular origin, the spatio-temporal distribution and the redox couple involved. Thus, a key task in the elucidation of the role of redox reactions is the specific and quantitative measurement of redox conditions with high spatio-temporal resolution. Unfortunately, until recently, our ability to perform such measurements was limited by the lack of adequate technology. Over the last 10 years, promising imaging tools have been developed from fluorescent proteins. Genetically encoded reactive oxygen species (ROS) and redox indicators (GERRIs) have the potential to allow real-time and pseudo-quantitative monitoring of specific ROS and thiol redox state in subcellular compartments or live organisms. Redox-sensitive yellow fluorescent proteins (rxYFP family), redox-sensitive green fluorescent proteins (roGFP family), HyPer (a probe designed to measure H2 O2 ), circularly permuted YFP and others have been used in several models and sufficient information has been collected to highlight their main characteristics. This review is intended to be a tour guide of the main types of GERRIs, their origins, properties, advantages and pitfalls.

  13. 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. PMID:23587877

  14. Dependence of particle concentration effect on pH and redox for arsenic removal by FeS-coated sand under anoxic conditions.

    PubMed

    Han, Young-Soo; Demond, Avery H; Gallegos, Tanya J; Hayes, Kim F

    2015-09-01

    FeS has been recognized as a good scavenger for arsenic under anoxic conditions. To create a suitable adsorbent for flow-through reactors such as permeable reactive barriers, it has been suggested that this material may be coated onto sand. However, previous work on FeS-coated sand has focused on batch reactors, while flow-through reactors usually have higher solid-solution ratios. To ascertain whether differences in the solid-solution ratio (SSR) are important in this system, batch sorption experiments were conducted as a function of pH using As(III) and FeS-coated sands at various solid-solution ratios. The results showed little variation in the distribution coefficient with SSR at pH 7 and 9. However, at pH 5, the results showed lower values of the distribution coefficient at lower SSRs, the reverse of typically reported SSR effects. Measured pe values showed a dependence on SSR, which, when coupled with chemical modeling of the Fe-As-S-H2O system, suggested a change in the removal mechanism with SSR, from adsorption to a reduced Fe(II) oxyhydroxide phase (represented by Fe2(OH)5) to precipitation as As2S3 or AsS. On the other hand, at pH 7 and 9, arsenite adsorption is the most probable removal mechanism regardless of the pe. Thus, this study identified variations in pH and redox conditions, and the removal mechanisms that these parameters govern, as the reason for the apparent SSR effect.

  15. 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. PMID:26657377

  16. 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).

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

    PubMed

    Rivet, Catherine A; Kniss-James, Ariel S; Gran, Margaret A; Potnis, Anish; Hill, Abby; Lu, Hang; Kemp, Melissa L

    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

  18. Endoplasmic reticulum stress triggers ROS signalling, changes the redox state, and regulates the antioxidant defence of Arabidopsis thaliana

    PubMed Central

    Turkan, Ismail

    2014-01-01

    Inefficient chaperone activity in endoplasmic reticulum (ER) causes accumulation of unfolded proteins and is called ER stress, which triggers the unfolded protein response. For proper oxidative protein folding, reactive oxygen species (ROS) such as H2O2 are produced in the ER. Although the role of ROS during abiotic stresses such as salinity is well documented, the role of ER-related ROS production and its signalling is not yet known. Moreover, how H2O2 production, redox regulation, and antioxidant defence are affected in salt-treated plants when ER protein-folding machinery is impaired needs to be elucidated. For this aim, changes in NADPH-oxidase-dependent ROS signalling and H2O2 content at sequential time intervals and after 48h of ER stress, induced by tunicamycin (Tm), salinity, and their combination were determined in Arabidopsis thaliana. The main root growth was inhibited by ER stress, while low levels of Tm caused an increase in lateral root density. Salt stress and Tm induced the expression of ER-stress-related genes (bZIP17, bZIP28, bZIP60, TIN1, BiP1, BiP3) and ERO1. Tm induced expression of RBOHD and RBOHF, which led to an early increase in H2O2 and triggered ROS signalling. This study is the first report that ER stress induces the antioxidant system and the Asada–Halliwell pathway of A. thaliana in a similar way to salinity. ER stress caused oxidative damage, as evident by increased H2O2 accumulation, lipid peroxidation, and protein oxidation. As a result, this study shows that ER stress triggers ROS signalling, changes the redox state, and regulates the antioxidant defence of A. thaliana. PMID:24558072

  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 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

  1. Chromium (VI) induced changes in growth and root plasma membrane redox activities in pea plants.

    PubMed

    Pandey, Vivek; Dixit, Vivek; Shyam, Radhey

    2009-03-01

    The effect of chromium (Cr) on growth as well as root plasma membrane redox reactions and superoxide radical production was studied in pea (Pisum sativum L. cv. Azad) plants exposed for 7 days to 20 and 200 microM Cr (VI), respectively, supplied as potassium dichromate. The growth of pea plants declined significantly at 200 microM Cr, as indicated by reduced leaf area and biomass. Relative to the control plants (no Cr exposure), the Cr content of roots increased significantly, both at 20 and 200 microM Cr. Following exposure to 200 microM Cr, there was a significant increase in root lipid peroxidation and hydrogen peroxide (H(2)O(2)) content, while both the Fv/Fm ratio and chlorophyll content were reduced. Exposure to Cr increased NADPH-dependent superoxide production in pea root plasma membrane vesicles, with the effect being more significant at 200 microM Cr than at 20 microM Cr. Treatment with Cr rapidly increased the activities of NADPH oxidase: relative to the controls, plants exposed to 20 microM Cr showed approximately a 67% increase in activity while there was a threefold increase in those plants exposed to 200 microM Cr. NADH-ferricyanide oxido-reductase activity was found to be inhibited by 16 and 51% at 20 and 200 microM Cr, respectively. The results of this study suggest that exposure to excess Cr damages pea root plasma membrane structure and function, resulting in decreased photosynthesis and poor plant growth.

  2. 48 CFR 52.243-5 - Changes and Changed Conditions.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... notify the Contracting Officer, in writing, of subsurface or latent physical conditions differing materially from those indicated in this contract or unknown unusual physical conditions at the site...

  3. 48 CFR 52.243-5 - Changes and Changed Conditions.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... notify the Contracting Officer, in writing, of subsurface or latent physical conditions differing materially from those indicated in this contract or unknown unusual physical conditions at the site...

  4. 48 CFR 52.243-5 - Changes and Changed Conditions.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... notify the Contracting Officer, in writing, of subsurface or latent physical conditions differing materially from those indicated in this contract or unknown unusual physical conditions at the site...

  5. [Morphogenetic changes during newt tail regeneration under changed gravity conditions].

    PubMed

    Radugina, E A; Grigorian, É N

    2012-01-01

    Gravity-dependent shape alterations in newt tail regenerates are described, which were previously noticed in experiments onboard satellites Foton M2, M3 and in corresponding laboratory controls. Laboratory conditions were developed that allow reproducing this phenomenon persistently in the adult newts Pleurodeles waltl (Michahelles, 1830). The newts kept in an aquarium (in partial weightlessness) after 1/3 tail amputation developed normal lanceolate regenerates, while those that stayed on a moist mat (exposed to greater gravity than in aquarium) developed curved tail regenerates. Dynamics of the shape alterations were described using computer morphometric analysis. The curve was shown to develop at stage III of regeneration and to be caused by bending of the developing axial structures: the ependymal tube and the cartilage rode. Cellular processes were described that accompany the tail shape changes, such as cell migration and formation of dense aggregates. Unequal proliferation throughout the wound epidermis and blastema was revealed using BrdU assay. Proliferation increased within dorsal and apical regions of the regenerates in the newts kept on the mat cell compared with the aquarian animals. PMID:23136735

  6. [Morphogenetic changes during newt tail regeneration under changed gravity conditions].

    PubMed

    Radugina, E A; Grigorian, É N

    2012-01-01

    Gravity-dependent shape alterations in newt tail regenerates are described, which were previously noticed in experiments onboard satellites Foton M2, M3 and in corresponding laboratory controls. Laboratory conditions were developed that allow reproducing this phenomenon persistently in the adult newts Pleurodeles waltl (Michahelles, 1830). The newts kept in an aquarium (in partial weightlessness) after 1/3 tail amputation developed normal lanceolate regenerates, while those that stayed on a moist mat (exposed to greater gravity than in aquarium) developed curved tail regenerates. Dynamics of the shape alterations were described using computer morphometric analysis. The curve was shown to develop at stage III of regeneration and to be caused by bending of the developing axial structures: the ependymal tube and the cartilage rode. Cellular processes were described that accompany the tail shape changes, such as cell migration and formation of dense aggregates. Unequal proliferation throughout the wound epidermis and blastema was revealed using BrdU assay. Proliferation increased within dorsal and apical regions of the regenerates in the newts kept on the mat cell compared with the aquarian animals.

  7. 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

  8. 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

  9. 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

  10. 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.

  11. Comparison of three thiol probes for determination of apoptosis-related changes in cellular redox status.

    PubMed

    Skindersoe, Mette E; Kjaerulff, Soeren

    2014-02-01

    An early step in apoptosis is extrusion of reduced glutathione (GSH). Current assays for measuring apoptosis involve a number of incubation and washing steps, making them time consuming and laborious. Using two novel thiol reactive agents (VitaBright-43 and VitaBright-48) and a GSH specific probe; monochlorobimane, we investigated whether changes in the level of free thiols can be used as an apoptotic marker. Upon addition to cells the probes permeate the cell membrane and react with intracellular thiols, causing cellular fluorescence. Cytometric quantification of the cell fluorescence (without washing) can then be used to determine the population's cellular thiol level at the single cell level. Apoptotic traits such as phosphatidylserine externalisation, caspase activity and mitochondrial potential were investigated at different time points after induction of apoptosis and correlated to changes detected using the thiol probes. We found that though all three thiol probes could be used to detect changes in the level of free thiols correlating well with apoptotic markers, other properties such as detection of early versus late apoptosis and staining kinetics differed among the three probes. However, we suggest adding evaluation of the level of free thiols to the list of phenotypes which may be measured in order to detect apoptosis, as this provides a reliable and easy way of assaying apoptosis. PMID:24222540

  12. The redox switch that regulates molecular chaperones.

    PubMed

    Conway, Myra E; Lee, Christopher

    2015-08-01

    Modification of reactive cysteine residues plays an integral role in redox-regulated reactions. Oxidation of thiolate anions to sulphenic acid can result in disulphide bond formation, or overoxidation to sulphonic acid, representing reversible and irreversible endpoints of cysteine oxidation, respectively. The antioxidant systems of the cell, including the thioredoxin and glutaredoxin systems, aim to prevent these higher and irreversible oxidation states. This is important as these redox transitions have numerous roles in regulating the structure/function relationship of proteins. Proteins with redox-active switches as described for peroxiredoxin (Prx) and protein disulphide isomerase (PDI) can undergo dynamic structural rearrangement resulting in a gain of function. For Prx, transition from cysteine sulphenic acid to sulphinic acid is described as an adaptive response during increased cellular stress causing Prx to form higher molecular weight aggregates, switching its role from antioxidant to molecular chaperone. Evidence in support of PDI as a redox-regulated chaperone is also gaining impetus, where oxidation of the redox-active CXXC regions causes a structural change, exposing its hydrophobic region, facilitating polypeptide folding. In this review, we will focus on these two chaperones that are directly regulated through thiol-disulphide exchange and detail how these redox-induced switches allow for dual activity. Moreover, we will introduce a new role for a metabolic protein, the branched-chain aminotransferase, and discuss how it shares common mechanistic features with these well-documented chaperones. Together, the physiological importance of the redox regulation of these proteins under pathological conditions such as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis will be discussed to illustrate the impact and importance of correct folding and chaperone-mediated activity.

  13. Hydrogeological Conditions Changes of Tomsk, Russia

    NASA Astrophysics Data System (ADS)

    Pokrovsky, V. D.; Dutova, E. M.; Kuzevanov, K. I.; Pokrovsky, D. S.; Nalivaiko, N. G.

    2015-11-01

    The hydro-geological conditions of Tomsk are determined by both natural factors and the impact of the urban infrastructure. Important impact on subsurface water flows involves the complex hydraulic relationship of several geological layers and the ancient and modern relief. Increasing groundwater abstraction has generally led to lowered piezometric heads in the deeper aquifer horizons, while in the uppermost horizons, rises in the water table and formation of new perched water tables are experienced due to leaking pipes and impedance of groundwater flow by deep foundations. In this paper special attention is paid to the Quaternary aquifer complex. Barrage effects of pile foundations and the intensive development of perched water distributed on flat surfaces of the watersheds and high terraces, complicated conditions for the construction and operation of facilities, leading in some cases to emergency situations.

  14. Topotactic redox chemistry of NaFeAs in water and air and superconducting behavior with stoichiometry change.

    SciTech Connect

    Todorov, I.; Chung, D. Y.; Claus, H.; Malliakas, C. D.; Douvalis, A. P.; Bakas, T.; He, J.; Dravid, V. P.; Kanatzidis, M. G.; Materials Science Division; Northwestern Univ.; Univ. of Ioannina

    2010-07-13

    We report experimental evidence that shows superconductivity in NaFeAs occurs when it is Na deficient. The oxidation of NaFeAs progresses differently in water and in air. In water the material oxidizes slowly and slightly retaining the original anti-PbFCl structure. In air NaFeAs oxidizes topotactically quickly and extensively transforming to the ThCr{sub 2}Si{sub 2} structure type. Water acts as a mild oxidizing agent on the FeAs layer by extracting electrons and Na{sup +} cations from the structure, while oxidation in air is more extensive and leads to change in structure type from NaFeAs to NaFe{sub 2}As{sub 2}. The superconducting transition temperature moves dramatically during the oxidation process. Exposed to water for an extended time period NaFeAs shows a substantial increase in T{sub c} up to 25 K with contraction of unit cell volume. NaFe{sub 2}As{sub 2}, the air oxidized product, shows T{sub c} of 12 K. We report detailed characterization of the redox chemistry and transformation of NaFeAs in water and air using single crystal and powder X-ray diffraction, magnetization studies, transmission electron microscopy, Moessbauer spectroscopy, pOH and elemental analysis.

  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. Sensing of redox status by TRP channels.

    PubMed

    Ogawa, Nozomi; Kurokawa, Tatsuki; Mori, Yasuo

    2016-08-01

    Cellular redox status is maintained by the balance between series of antioxidant systems and production of reactive oxygen/nitrogenous species. Cells utilize this redox balance to mediate diverse physiological functions. Transient receptor potential (TRP) channels are non-selective cation channels that act as biosensors for environmental and noxious stimuli, such as capsaicin and allicin, as well as changes in temperature and conditions inside the cell. TRP channels also have an emerging role as essential players in detecting cellular redox status to regulate cellular signals mediating physiological phenomena. Reactive species activate TRP channels either directly through oxidative amino acid modifications or indirectly through second messengers. For instance, TRPA1, TRPV1 and TRPC5 channels are directly activated by oxidizing agents through cysteine modification; whereas, TRPM2 channel is indirectly activated by production of ADP-ribose. One intriguing property of several TRP channels is susceptibility to both oxidizing and reducing stimuli, suggesting TRP channels could potentially act as a bidirectional sensor for detecting deviations in redox status. In this review, we discuss the unique chemical physiologies of redox sensitive TRP channels and their physiological significance in Ca(2+) signaling. PMID:26969190

  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. 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

  19. 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

  20. Superoxide Dismutase 1 Loss Disturbs Intracellular Redox Signaling, Resulting in Global Age-Related Pathological Changes

    PubMed Central

    2014-01-01

    Aging is characterized by increased oxidative stress, chronic inflammation, and organ dysfunction, which occur in a progressive and irreversible manner. Superoxide dismutase (SOD) serves as a major antioxidant and neutralizes superoxide radicals throughout the body. In vivo studies have demonstrated that copper/zinc superoxide dismutase-deficient (Sod1−/−) mice show various aging-like pathologies, accompanied by augmentation of oxidative damage in organs. We found that antioxidant treatment significantly attenuated the age-related tissue changes and oxidative damage-associated p53 upregulation in Sod1−/− mice. This review will focus on various age-related pathologies caused by the loss of Sod1 and will discuss the molecular mechanisms underlying the pathogenesis in Sod1−/− mice. PMID:25276767

  1. 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.

  2. 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…

  3. Postural responses to changing task conditions.

    PubMed

    Hansen, P D; Woollacott, M H; Debu, B

    1988-01-01

    The experimental goal was to investigate discrepancies in the literature concerning postural adaptation and to determine if the prior presentation of horizontal perturbations affected the amplitude of responses to rotational perturbations. Surface EMG recordings from lower leg muscles (gastrocnemius (GAS) and tibialis anterior (TA)) were recorded in twelve subjects, and the amplitudes of the responses were statistically analyzed. We did not find differences between the responses to rotational perturbations which preceded or followed horizontal perturbations. This finding did not support the hypothesis that differences in the order of presentation of the different types of perturbations accounted for the discrepancies in the literature. Furthermore, our design did not show the progressive elimination of the GAS response within three to five sequential trials. Instead, we found a slow but significant response amplitude reduction over ten trials without yielding a permanent disappearance of the response. When analyzing the GAS responses to the rotational perturbations only, we found two components that contributed to the response reduction: 1) an initial reduction between trials one and subsequent trials, which could be due to habituation of a startle-like response; and 2) a second reduction which was more gradual. Our results also showed an immediate change in the response amplitude on the first trial, when the type of perturbation was changed. This is inconsistent with the view that ankle musculature stretch and joint movement are the primary inputs driving the postural responses. Since small ankle dorsiflexing rotations produced by the platform translations caused large GAS responses while large ankle dorsiflexing rotations produced by direct platform rotations caused small GAS responses, this suggests that multiple sensory inputs contribute to the responses. We propose that an initial compensation to a new perturbation type occurs within the first trial by the

  4. 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

  5. Quantitative measures for redox signaling.

    PubMed

    Pillay, Ché S; Eagling, Beatrice D; Driscoll, Scott R E; Rohwer, Johann M

    2016-07-01

    Redox signaling is now recognized as an important regulatory mechanism for a number of cellular processes including the antioxidant response, phosphokinase signal transduction and redox metabolism. While there has been considerable progress in identifying the cellular machinery involved in redox signaling, quantitative measures of redox signals have been lacking, limiting efforts aimed at understanding and comparing redox signaling under normoxic and pathogenic conditions. Here we have outlined some of the accepted principles for redox signaling, including the description of hydrogen peroxide as a signaling molecule and the role of kinetics in conferring specificity to these signaling events. Based on these principles, we then develop a working definition for redox signaling and review a number of quantitative methods that have been employed to describe signaling in other systems. Using computational modeling and published data, we show how time- and concentration- dependent analyses, in particular, could be used to quantitatively describe redox signaling and therefore provide important insights into the functional organization of redox networks. Finally, we consider some of the key challenges with implementing these methods. PMID:27151506

  6. 49 CFR 1542.107 - Changed conditions affecting security.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... § 1542.103; or (3) Layout or physical structure of any area under the control of the airport operator... notification of the change condition(s). TSA will notify the airport operator of the disposition of...

  7. 49 CFR 1542.107 - Changed conditions affecting security.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... § 1542.103; or (3) Layout or physical structure of any area under the control of the airport operator... notification of the change condition(s). TSA will notify the airport operator of the disposition of...

  8. Morphine Induces Redox-Based Changes in Global DNA Methylation and Retrotransposon Transcription by Inhibition of Excitatory Amino Acid Transporter Type 3–Mediated Cysteine Uptake

    PubMed Central

    Trivedi, Malav; Shah, Jayni; Hodgson, Nathaniel; Byun, Hyang-Min

    2014-01-01

    Canonically, opioids influence cells by binding to a G protein–coupled opioid receptor, initiating intracellular signaling cascades, such as protein kinase, phosphatidylinositol 3-kinase, and extracellular receptor kinase pathways. This results in several downstream effects, including decreased levels of the reduced form of glutathione (GSH) and elevated oxidative stress, as well as epigenetic changes, especially in retrotransposons and heterochromatin, although the mechanism and consequences of these actions are unclear. We characterized the acute and long-term influence of morphine on redox and methylation status (including DNA methylation levels) in cultured neuronal SH-SY5Y cells. Acting via μ-opioid receptors, morphine inhibits excitatory amino acid transporter type 3–mediated cysteine uptake via multiple signaling pathways, involving different G proteins and protein kinases in a temporal manner. Decreased cysteine uptake was associated with decreases in both the redox and methylation status of neuronal cells, as defined by the ratios of GSH to oxidized forms of glutathione and S-adenosylmethionine to S-adenosylhomocysteine levels, respectively. Further, morphine induced global DNA methylation changes, including CpG sites in long interspersed nuclear elements (LINE-1) retrotransposons, resulting in increased LINE-1 mRNA. Together, these findings illuminate the mechanism by which morphine, and potentially other opioids, can influence neuronal-cell redox and methylation status including DNA methylation. Since epigenetic changes are implicated in drug addiction and tolerance phenomenon, this study could potentially extrapolate to elucidate a novel mechanism of action for other drugs of abuse. PMID:24569088

  9. General Chemoselective and Redox-Responsive Ligation and Release Strategy

    PubMed Central

    2015-01-01

    We report a switchable redox click and cleave reaction strategy for conjugating and releasing a range of molecules on demand. This chemoselective redox-responsive ligation (CRRL) and release strategy is based on a redox switchable oxime linkage that is controlled by mild chemical or electrochemical redox signals and can be performed at physiological conditions without the use of a catalyst. Both conjugation and release reactions are kinetically well behaved and quantitative. The CRRL strategy is synthetically modular and easily monitored and characterized by routine analytical techniques. We demonstrate how the CRRL strategy can be used for the dynamic generation of cyclic peptides and the ligation of two different peptides that are stable but can be selectively cleaved upon changes in the redox environment. We also demonstrate a new redox based delivery of cargoes to live cells strategy via the CRRL methodology by synthesizing a FRET redox-responsive probe that is selectively activated within a cellular environment. We believe the ease of the CRRL strategy should find wide use in a range of applications in biology, tissue engineering, nanoscience, synthetic chemistry, and material science and will expand the suite of current conjugation and release strategies. PMID:24559434

  10. 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

  11. Carbon speciation in the asthenosphere: Experimental measurements of the redox conditions at which carbonate-bearing melts coexist with graphite or diamond in peridotite assemblages

    NASA Astrophysics Data System (ADS)

    Stagno, Vincenzo; Frost, Daniel J.

    2010-11-01

    The speciation of carbon in the Earth's mantle is largely governed by oxygen fugacity. Under reducing conditions carbon forms graphite, diamond or CH 4, while under more oxidising conditions carbonate minerals or CO 2-bearing melts or fluids are stable. Using an Ir-Fe alloy sliding redox sensor we have measured the oxygen fugacity at which carbon (graphite or diamond) oxidises to carbonate minerals or melts within mantle peridotite assemblages between 2.5 and 11 GPa at 1100-1600 °C. The experiments were performed up to temperatures where carbonate melts evolve towards more silicate-rich compositions. The dilution of the carbonate melt component lowers the relative fo 2, expanding the melt stability field with respect to reduced carbon. We parameterise our results for the a Ca-bearing system as a function of P (in bars), T (K) and mole fraction of CO 2 ( XCO 2) in the melt with the equation. Logfo=5.44 - 21380/T+0.078P-1/T+Log X This expression reproduces our experimental results to within 0.3 log units between 2.5 and 11 GPa. A further equation is fitted to Ca-free results. Studies indicate that garnet peridotite mantle rocks become progressively more reduced with depth due to the effects of pressure on the governing ferric/ferrous equilibria. It has been proposed that small degree carbonate-rich melts may form at depths up to 300 km beneath mid ocean ridges; however, if the current garnet peridotite oxy-thermometer is correct then our results indicate that the fo 2 of peridotitic mantle will remain in the diamond/graphite stability field up to at least 100-150 km depth. Only at depths shallower than 150 km would Fe 3+ in mantle silicates react with graphite to produce carbonate-rich melts in a redox melting process. Redox melting, therefore, limits the depth interval over which carbonate-rich melts can form beneath ridges. If current estimates for the effect of pressure on mantle fo 2 in the garnet peridotite stability field are correct, graphite or diamond

  12. Changes in the redox state and endogenous fluorescence of in vivo human skin due to intrinsic and photo-aging, measured by multiphoton tomography with fluorescence lifetime imaging

    NASA Astrophysics Data System (ADS)

    Sanchez, Washington Y.; Obispo, Clara; Ryan, Elizabeth; Grice, Jeffrey E.; Roberts, Michael S.

    2013-06-01

    Ultraviolet radiation from solar exposure is a key extrinsic factor responsible for premature skin aging (i.e., photo-aging). Recent advances using in vivo multiphoton tomography (MPT) demonstrate the efficacy of this approach to assess intrinsic and extrinsic skin aging as an alternative to existing invasive techniques. In this study, we measured changes in epidermal autofluorescence, dermal collagen second harmonic generation (SHG), and the redox state of solar-exposed and solar-protected human skin by MPT with fluorescence lifetime imaging (MPT-FLIM). Twenty-four volunteers across four age categories (20 to 29, 30 to 39, 40 to 49, and 50 to 59 years old; six volunteers each) were recruited for MPT-FLIM imaging of the dorsal (solar-exposed; photo-damaged) and volar (solar-protected) forearm. We demonstrate a higher intensity of dermal collagen SHG within the volar forearm compared to dorsal solar-exposed skin. Redox imaging of each epidermal skin stratum by FLIM demonstrates an increase in fluorescence lifetime in the solar-exposed dorsal forearm that is more apparent in aged skin. The results of this study suggest the redox state of the viable epidermis is a key marker in assessing intrinsic and photo-damage skin aging, in combination with changes in autofluorescence and SHG.

  13. 49 CFR 1542.107 - Changed conditions affecting security.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... SECURITY ADMINISTRATION, DEPARTMENT OF HOMELAND SECURITY CIVIL AVIATION SECURITY AIRPORT SECURITY Airport Security Program § 1542.107 Changed conditions affecting security. (a) After approval of the security... 49 Transportation 9 2013-10-01 2013-10-01 false Changed conditions affecting security....

  14. 49 CFR 1542.107 - Changed conditions affecting security.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... SECURITY ADMINISTRATION, DEPARTMENT OF HOMELAND SECURITY CIVIL AVIATION SECURITY AIRPORT SECURITY Airport Security Program § 1542.107 Changed conditions affecting security. (a) After approval of the security... 49 Transportation 9 2014-10-01 2014-10-01 false Changed conditions affecting security....

  15. α-Tocopherol administration blocks adaptive changes in cell NADH/NAD+ redox state and mitochondrial function leading to inhibition of gastric mucosa cell proliferation in rats.

    PubMed

    Olguín-Martínez, Marisela; Hernández-Espinosa, Diego R; Hernández-Muñoz, Rolando

    2013-12-01

    In experimentally induced chronic gastritis, a compensatory mucosal cell proliferation occurs with enhanced glucose oxidative metabolism linked to lipoperoxidative events. Therefore, this study was aimed at assessing the participation of cell NAD/NADH redox state and mitochondrial functions during gastric mucosa proliferation and the effects of in vivo α-tocopherol (vitamin E) administration. Glucose oxidation and oxygen consumption were tested in gastric mucosa samples obtained from rats with gastritis and from those also treated with α-tocopherol. Gastric mucosal mitochondria were isolated and structural and functional parameters were determined. Succinate oxidation, ADP phosphorylation, mitochondrial enzyme activities, and membrane lipid composition were measured. In addition, parameters indicative of cellular NAD/NADH redox state, proliferation, apoptosis, and nitric oxide (NO) metabolism were also determined. After ethanol withdrawal, the damaged gastric mucosa increased glucose and oxygen consumption, events associated with a more reduced cytoplasmic NAD/NADH ratio. Enhanced mitochondrial oxidative phosphorylation and increased mitochondrial enzyme activities occurred early, accompanied by recovery of lost mitochondrial protein and lipid composition in the gastric mucosa, events associated with increased NO production. When mitochondrial function and structural events were normalized, apoptosis was initiated as assessed by the mitochondrial Bax/Bcl2 ratio. Treatment with α-tocopherol inhibited cell proliferation and blocked enhanced glucose utilization, mitochondrial substrate oxidation, and changes in redox state, delaying the onset of these adaptive metabolic changes, whereas it inhibited cell proliferation. In conclusion, α-tocopherol could abolish damage-induced "stress" signaling by desynchronizing mitochondrial adaptive responses, including mitochondria biogenesis, and consequently NAD/NADH redox, which seems to regulate gastric mucosal cell

  16. α-Tocopherol administration blocks adaptive changes in cell NADH/NAD+ redox state and mitochondrial function leading to inhibition of gastric mucosa cell proliferation in rats.

    PubMed

    Olguín-Martínez, Marisela; Hernández-Espinosa, Diego R; Hernández-Muñoz, Rolando

    2013-12-01

    In experimentally induced chronic gastritis, a compensatory mucosal cell proliferation occurs with enhanced glucose oxidative metabolism linked to lipoperoxidative events. Therefore, this study was aimed at assessing the participation of cell NAD/NADH redox state and mitochondrial functions during gastric mucosa proliferation and the effects of in vivo α-tocopherol (vitamin E) administration. Glucose oxidation and oxygen consumption were tested in gastric mucosa samples obtained from rats with gastritis and from those also treated with α-tocopherol. Gastric mucosal mitochondria were isolated and structural and functional parameters were determined. Succinate oxidation, ADP phosphorylation, mitochondrial enzyme activities, and membrane lipid composition were measured. In addition, parameters indicative of cellular NAD/NADH redox state, proliferation, apoptosis, and nitric oxide (NO) metabolism were also determined. After ethanol withdrawal, the damaged gastric mucosa increased glucose and oxygen consumption, events associated with a more reduced cytoplasmic NAD/NADH ratio. Enhanced mitochondrial oxidative phosphorylation and increased mitochondrial enzyme activities occurred early, accompanied by recovery of lost mitochondrial protein and lipid composition in the gastric mucosa, events associated with increased NO production. When mitochondrial function and structural events were normalized, apoptosis was initiated as assessed by the mitochondrial Bax/Bcl2 ratio. Treatment with α-tocopherol inhibited cell proliferation and blocked enhanced glucose utilization, mitochondrial substrate oxidation, and changes in redox state, delaying the onset of these adaptive metabolic changes, whereas it inhibited cell proliferation. In conclusion, α-tocopherol could abolish damage-induced "stress" signaling by desynchronizing mitochondrial adaptive responses, including mitochondria biogenesis, and consequently NAD/NADH redox, which seems to regulate gastric mucosal cell

  17. 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.

  18. Redox compartmentalization in eukaryotic cells

    PubMed Central

    Go, Young-Mi; Jones, Dean P.

    2008-01-01

    Diverse functions of eukaryotic cells are optimized by organization of compatible chemistries into distinct compartments defined by the structures of lipid-containing membranes, multiprotein complexes and oligomeric structures of saccharides and nucleic acids. This structural and chemical organization is coordinated, in part, through cysteine residues of proteins which undergo reversible oxidation-reduction and serve as chemical/structural transducing elements. The central thiol/disulfide redox couples, thioredoxin-1, thioredoxin-2, GSH/GSSG and cysteine/cystine (Cys/CySS), are not in equilibrium with each other and are maintained at distinct, non-equilibrium potentials in mitochondria, nuclei, the secretory pathway and the extracellular space. Mitochondria contain the most reducing compartment, have the highest rates of electron transfer and are highly sensitive to oxidation. Nuclei also have more reduced redox potentials but are relatively resistant to oxidation. The secretory pathway contains oxidative systems which introduce disulfides into proteins for export. The cytoplasm contains few metabolic oxidases and this maintains an environment for redox signaling dependent upon NADPH oxidases and NO synthases. Extracellular compartments are maintained at stable oxidizing potentials. Controlled changes in cytoplasmic GSH/GSSG redox potential are associated with functional state, varying with proliferation, differentiation and apoptosis. Variation in extracellular Cys/CySS redox potential is also associated with proliferation, cell adhesion and apoptosis. Thus, cellular redox biology is inseparable from redox compartmentalization. Further elucidation of the redox control networks within compartments will improve the mechanistic understanding of cell functions and their disruption in disease. PMID:18267127

  19. 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.

  20. 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.

  1. 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

  2. Automated and continuous redox potential measurements in soil.

    PubMed

    Vorenhout, Michel; van der Geest, Harm G; van Marum, Daan; Wattel, Kees; Eijsackers, Herman J P

    2004-01-01

    Redox potential (Eh) describes the electrical state of a matrix. In soils, Eh is an important parameter controlling the persistence of many organic and inorganic compounds. A popular, but also criticized, manual measuring method makes use of a small tip of Pt placed on a copper wire that is placed in the soil; a reference electrode is placed in the same soil at a fixed distance. Fluctuations in redox potential values measured in the soil can be very large and depth-dependent. This will be overlooked when making single-point measurements. We developed the datalogger Hypnos 2.0 for continuous redox potential and temperature measurements at various depths in the soil and without disturbance of the site. Hypnos is field-deployable, relatively cheap, and runs on batteries. The datalogger can use a "sleep mode" between sampling events. In sleep mode, there is no constant voltage on the Pt wire or the reference electrode, but there is only a short pulse during sampling. We did not measure an effect of this short pulse on the measured redox potential. In sandy soils in mesocosms and in a salt marsh soil we measured changes in the Eh as large as from -400 to +100 mV within 4 d, and daily cycles of 200 mV. Both absolute redox potential values and their diurnal variations were depth-dependent. Because single redox measurements are insufficient in describing redox conditions in some soil systems, Hypnos can be a powerful tool when studying the effects of fluctuating redox conditions on metal availability and pollutant degradation.

  3. Redox regulation in the thylakoid lumen.

    PubMed

    Kang, Zhen-Hui; Wang, Gui-Xue

    2016-03-15

    Higher plants need to balance the efficiency of light energy absorption and dissipative photo-protection when exposed to fluctuations in light quantity and quality. This aim is partially realized through redox regulation within the chloroplast, which occurs in all chloroplast compartments except the envelope intermembrane space. In contrast to the chloroplast stroma, less attention has been paid to the thylakoid lumen, an inner, continuous space enclosed by the thylakoid membrane in which redox regulation is also essential for photosystem biogenesis and function. This sub-organelle compartment contains at least 80 lumenal proteins, more than 30 of which are known to contain disulfide bonds. Thioredoxins (Trx) in the chloroplast stroma are photo-reduced in the light, transferring reducing power to the proteins in the thylakoid membrane and ultimately the lumen through a trans-thylakoid membrane-reduced, equivalent pathway. The discovery of lumenal thiol oxidoreductase highlights the importance of the redox regulation network in the lumen for controlling disulfide bond formation, which is responsible for protein activity and folding and even plays a role in photo-protection. In addition, many lumenal members involved in photosystem assembly and non-photochemical quenching are likely required for reduction and/or oxidation to maintain their proper efficiency upon changes in light intensity. In light of recent findings, this review summarizes the multiple redox processes that occur in the thylakoid lumen in great detail, highlighting the essential auxiliary roles of lumenal proteins under fluctuating light conditions. PMID:26812087

  4. 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.

  5. 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

  6. 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

  7. Redox regulation in cancer

    PubMed Central

    Das, Ila; Chandhok, Des

    2010-01-01

    Oxidative stress, implicated in the etiology of cancer, results from an imbalance in the production of reactive oxygen species (ROS) and cell’s own antioxidant defenses. ROS deregulate the redox homeostasis and promote tumor formation by initiating an aberrant induction of signaling networks that cause tumorigenesis. Ultraviolet (UV) exposures, γ-radiation and other environmental carcinogens generate ROS in the cells, which can exert apoptosis in the tumors, thereby killing the malignant cells or induce the progression of the cancer growth by blocking cellular defense system. Cancer stem cells take the advantage of the aberrant redox system and spontaneously proliferate. Oxidative stress and gene-environment interactions play a significant role in the development of breast, prostate, pancreatic and colon cancer. Prolonged lifetime exposure to estrogen is associated with several kinds of DNA damage. Oxidative stress and estrogen receptor-associated proliferative changes are suggested to play important roles in estrogen-induced breast carcinogenesis. BRCA1, a tumor suppressor against hormone responsive cancers such as breast and prostate cancer, plays a significant role in inhibiting ROS and estrogen mediated DNA damage; thereby regulate the redox homeostasis of the cells. Several transcription factors and tumor suppressors are involved during stress response such as Nrf2, NFκB and BRCA1. A promising strategy for targeting redox status of the cells is to use readily available natural substances from vegetables, fruits, herbs and spices. Many of the phytochemicals have already been identified to have chemopreventive potential, capable of intervening in carcinogenesis. PMID:20716925

  8. Redox-Dependent Modulation of Anthocyanin Biosynthesis by the TCP Transcription Factor TCP15 during Exposure to High Light Intensity Conditions in Arabidopsis1[OPEN

    PubMed Central

    Viola, Ivana L.; 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. PMID:26574599

  9. 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. PMID:26574599

  10. 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.

  11. 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.

  12. Episodic Enhanced Carbon Sequestration and Redox Conditions in a Late Barremian-Early Aptian Restricted Marine Basin: El Pui Section, Organyà Basin

    NASA Astrophysics Data System (ADS)

    Sanchez-hernandez, Y.; Maurrasse, F. J.

    2013-05-01

    A major episode of intensified carbon sequestration (TOC) and enhanced redox conditions in the lower Cretaceous is associated with the well-known Oceanic Anoxic Event 1a (OAE1a) worldwide. Increased TOC values (up to 3.0wt%) concurrent with positive excursions in δ13C (up to 2.5‰) have been documented in different areas in the Late Barremian as well as in the middle Aptian prior to, and after OAE-1a, respectively. Such indicators imply that environmental conditions conducive to increased carbon sequestration (although less intense) developed in isolated basins not synchronous with major global forcing mechanisms recorded in the major events. In this study, geochemical analyses: organic (TOC; δ13C; biomarker analysis), and inorganic: (trace and major element concentrations, and clay mineralogy) reveal the occurrence of intermittent reducing conditions in a restricted marine basin from the latest Barremian to the lower Aptian that led to enhanced C sequestration. We also document later occurrence of OAE-1a in the basin sedimentary succession, and the impact of regional physiographic conditions in the local expression of the global event. Temporal behavior in the concentration of major elements (Al, Si and Ti) reveals variations in sedimentation patterns and nutrient availability controlled by fluctuation in terrigenous fluxes from continental runoffs. Such fluctuations controlled primary producers (both Prokaryotes: cyanobacteria; and Eukaryotes: nanno-phytoplankton) that constitute the calcareous and organic matter (OM) components of the matrix where their relative abundance co-varies with the intensity of terrigenous fluxes. The presence of benthic fauna also responded to episodic alterations in the oxygen levels with lower abundance or absence at dysoxic to anoxic intervals. Oxygen depleted levels are associated with enhanced primary productivity as indicated by positive excursions in the δ13C-org and trace element indices.

  13. 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.

  14. 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

  15. Redox regulated peroxisome homeostasis.

    PubMed

    Wang, Xiaofeng; Li, Shuo; Liu, Yu; Ma, Changle

    2015-01-01

    Peroxisomes are ubiquitous organelles present in nearly all eukaryotic cells. Conserved functions of peroxisomes encompass beta-oxidation of fatty acids and scavenging of reactive oxygen species generated from diverse peroxisomal metabolic pathways. Peroxisome content, number, and size can change quickly in response to environmental and/or developmental cues. To achieve efficient peroxisome homeostasis, peroxisome biogenesis and degradation must be orchestrated. We review the current knowledge on redox regulated peroxisome biogenesis and degradation with an emphasis on yeasts and plants.

  16. Redox regulated peroxisome homeostasis.

    PubMed

    Wang, Xiaofeng; Li, Shuo; Liu, Yu; Ma, Changle

    2015-01-01

    Peroxisomes are ubiquitous organelles present in nearly all eukaryotic cells. Conserved functions of peroxisomes encompass beta-oxidation of fatty acids and scavenging of reactive oxygen species generated from diverse peroxisomal metabolic pathways. Peroxisome content, number, and size can change quickly in response to environmental and/or developmental cues. To achieve efficient peroxisome homeostasis, peroxisome biogenesis and degradation must be orchestrated. We review the current knowledge on redox regulated peroxisome biogenesis and degradation with an emphasis on yeasts and plants. PMID:25545794

  17. Growth temperature-induced changes in biomass accumulation, photosynthesis and glutathione redox homeostasis as influenced by hydrogen peroxide in cucumber.

    PubMed

    Li, Hao; Wang, Xue Min; Chen, Li; Ahammed, Golam Jalal; Xia, Xiao Jian; Shi, Kai; Considine, Michael J; Yu, Jing Quan; Zhou, Yan Hong

    2013-10-01

    Hydrogen peroxide (H2O2) and glutathione (GSH) are involved in the stress response in plants. To elucidate the role of H2O2 in the acclimation of CO2 assimilation under sub- or supra-optimal growth temperatures, we examined the effect and interaction of H2O2 manipulation on the photosynthetic metabolism of cucumber plants (Cucumis sativus L.) grown under five temperature regimes spanning above and below the optimal growth temperature; 11/9, 18/15, 25/20, 32/27, and 39/33 °C (day/night), with or without dimethylthiourea (DMTU) or H2O2 treatment. As expected, exposure to sub- or supra-optimal growth temperatures resulted in decreased plant growth, associated with a decline in CO2 assimilation (Asat), Rubisco content, and activities of enzymes involved in the CO2 assimilation, as well as a decrease in the ratio of reduced (GSH) to oxidized (GSSG) glutathione (GSH/GSSG). Foliar application of H2O2 promoted, whilst DMTU retarded the capacity of plants to acclimate to non-optimal growth temperatures; this was consistently shown in altered activity of redox-sensitive enzymes involved in CO2 assimilation. These results strongly suggest that the influence of growth temperature on CO2 assimilation was primarily targeted at the activities of the redox-sensitive enzymes of CO2 assimilation. Meanwhile, the data suggest that the cellular H2O2 level is an important signal for the glutathione-dependent regulation of redox-sensitive enzymes of CO2 assimilation in cucumber plants.

  18. 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.

  19. Ferric iron content of ferropericlase as a function of composition, oxygen fugacity, temperature and pressure: Implications for redox conditions during diamond formation in the lower mantle

    NASA Astrophysics Data System (ADS)

    Otsuka, Kazuhiko; Longo, Micaela; McCammon, Catherine A.; Karato, Shun-ichiro

    2013-03-01

    We investigated the ferric iron (Fe3+) concentration in (Mg,Fe)O ferropericlase using the flank method applied to Mg-Fe interdiffusion couples of ferropericlase. Diffusion couples with Mg/(Mg+Fe) in the range 0.44 to 1 were annealed at temperatures of 1673-1873 K and pressures of 5-24 GPa over a wide range of oxygen fugacities. Oxygen fugacity was controlled by Fe, Ni, Mo, and Re metal capsules and their corresponding oxide phases. Based on our results and available experimental data, we derived an equation for the Fe3+ solubility in ferropericlase applicable to depths at the top of the lower mantle: [Fe3+]=C (XFe4fO2)m exp{-((1-XFe)E*Mg+XFeE*Fe+PV*)/RT}, where C=2.6(1)×10-3, m=0.114(3), E*Mg=-35(3) [kJ/mol], E*Fe=-98(2) [kJ/mol], and V*=2.09(3) [cm3/mol]. The value of the oxygen fugacity exponent m implies that Fe3+ mostly occupies tetrahedral sites under these conditions, which is consistent with the results of previously reported Mössbauer spectroscopy studies. Based on this relationship, we calculated the redox conditions of ferropericlase inclusions in diamonds believed to have come from the lower mantle. The estimated oxygen fugacities are close to the upper stability limit of diamond in mantle peridotite at the top of the lower mantle at adiabatic or slightly superadiabatic temperatures, which suggests that ferropericlase inclusions recorded and preserved the conditions at which diamond was precipitated from carbonates or carbonatite melts near the top of the lower mantle.

  20. [Effects of technological additives and heating range on some chemical and physical changes in canned meat. 2. Changes in redox potentials and selected quality characteristics].

    PubMed

    Wojciechowski, J; Pikul, J; Janitz, W

    1976-01-01

    The influence of technological additives and the range of heating on the redox potential, as well as on some quality features of canned meat was examined. The experiments showed, that the time of storage and the degree of heating of model preserves of meat influence on the redox potential. The technological additions as polyphosphates, ascorbic acid, gelatine and mixtures of these substances influence less on the redox potential. The analysis of each experimental factor showed, that on the secretion of meat juice occurring during can pasteurization or sterilization influence all experimental factors, as the kind of heating, the time of storage as well as the kind and the quantity of technological additives. The highest secretion of meat juice was found in cans with addition of ascorbic acid. Cans with addition of gelatine had the smallest content of jelly and consequently the lowest secretion of meat juice. It was also found a certain relation between the level of redox potential and the tested quality features of the model meat preserves.

  1. Ontogenetic changes in the neural mechanisms of eyeblink conditioning.

    PubMed

    Freeman, J H; Nicholson, D A

    2001-01-01

    The rodent eyeblink conditioning paradigm is an ideal model system for examining the relationship between neural maturation and the ontogeny of associative learning. Elucidation of the neural mechanisms underlying the ontogeny of learning is tractable using eyeblink conditioning because the necessary neural circuitry (cerebellum and interconnected brainstem nuclei) underlying the acquisition and retention of the conditioned response (CR) has been identified in adult organisms. Moreover, the cerebellum exhibits substantial postnatal anatomical and physiological maturation in rats. The eyeblink CR emerges developmentally between postnatal day (PND) 17 and 24 in rats. A series of experiments found that the ontogenetic emergence of eyeblink conditioning is related to the development of associative learning and not related to changes in performance. More recent studies have examined the relationship between the development of eyeblink conditioning and the physiological maturation of the cerebellum, a brain structure that is necessary for eyeblink conditioning in adult organisms. Disrupting cerebellar development with lesions or antimitotic treatments impairs the ontogeny of eyeblink conditioning. Studies of the development of physiological processes within the cerebellum have revealed striking ontogenetic changes in stimulus-elicited and learning-related neuronal activity. Neurons in the interpositus nucleus and Purkinje cells in the cortex exhibit developmental increases in neuronal discharges following the unconditioned stimulus (US) and in neuronal discharges that model the amplitude and time-course of the eyeblink CR. The developmental changes in CR-related neuronal activity in the cerebellum suggest that the ontogeny of eyeblink conditioning depends on the development of mechanisms that establish cerebellar plasticity. Learning and the induction of neural plasticity depend on the magnitude of the US input to the cerebellum. The role of developmental changes in the

  2. Neutral sphingomyelinase-2 is a redox sensitive enzyme: role of catalytic cysteine residues in regulation of enzymatic activity through changes in oligomeric state.

    PubMed

    Dotson, P Patrick; Karakashian, Alexander A; Nikolova-Karakashian, Mariana N

    2015-02-01

    Neutral sphingomyelinase-2 (nSMase-2) is the major sphingomyelinase activated in response to pro-inflammatory cytokines and during oxidative stress. It is a membrane-bound 655 amino acid protein containing 22 cysteine residues. In this study, we expressed recombinant mouse nSMase-2 protein in Escherichia coli, and investigated whether nSMase-2 is a redox sensitive enzyme. Our results demonstrate that nSMase-2 exists as both monomers and multimers that are associated with high and low enzymatic activity respectively. Mutational analysis of nSMase-2 identified within its C-terminal catalytic domain several oxidant-sensitive cysteine residues that were shown to be involved in enzyme oligomerization. Changing Cys(617) to Ser for example is a gain-of-function mutation associated with a decreased propensity for oligomerization. Alternatively, nSMase-2 expression in a bacterial strain that lacks endogenous thioredoxin, Rosetta-gami2, results in increased oligomer formation and lower enzyme activity. Phenotypic rescue was accomplished by treating nSMase-2 lysates with recombinant human thioredoxin. This indicates that nSMase-2 may be a novel substrate for thioredoxin. FRET analysis confirmed the presence of nSMase-2 multimers in mammalian HEK cells and their localization to the plasma membrane. In conclusion, our results identify nSMase-2 as a redox-sensitive enzyme, whose basal activity is influenced by thioredoxin-mediated changes in its oligomeric state. PMID:25287744

  3. 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

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

    PubMed

    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.

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

    PubMed

    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

  6. Responding changes systematically within sessions during conditioning procedures.

    PubMed

    McSweeney, F K; Roll, J M

    1993-11-01

    When the procedure is held constant within an experimental session, responding often changes systematically within that session. Many of these within-session changes in responding cannot be dismissed as learning curves or by-products of satiation. They have been observed in studies of positive reinforcement, avoidance, punishment, extinction, discrimination, delayed matching to sample, concept formation, maze and alley running, and laboratory analogues of foraging, as well as in the unconditioned substrates of conditioned behavior. When aversive stimuli are used, responding usually increases early in the session. When positive reinforcers are used, responding changes in a variety of ways, including increasing, decreasing, and bitonic functions. Both strong and minimal reinforcement procedures produce within-session decreases in positively reinforced behavior. Within-session changes in responding have substantial theoretical and methodological implications for research in conditioning. PMID:8283153

  7. Responding changes systematically within sessions during conditioning procedures.

    PubMed Central

    McSweeney, F K; Roll, J M

    1993-01-01

    When the procedure is held constant within an experimental session, responding often changes systematically within that session. Many of these within-session changes in responding cannot be dismissed as learning curves or by-products of satiation. They have been observed in studies of positive reinforcement, avoidance, punishment, extinction, discrimination, delayed matching to sample, concept formation, maze and alley running, and laboratory analogues of foraging, as well as in the unconditioned substrates of conditioned behavior. When aversive stimuli are used, responding usually increases early in the session. When positive reinforcers are used, responding changes in a variety of ways, including increasing, decreasing, and bitonic functions. Both strong and minimal reinforcement procedures produce within-session decreases in positively reinforced behavior. Within-session changes in responding have substantial theoretical and methodological implications for research in conditioning. PMID:8283153

  8. 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

  9. 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.

  10. Future Risks of Pest Species under Changing Climatic Conditions.

    PubMed

    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

  11. 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

  12. Future Risks of Pest Species under Changing Climatic Conditions.

    PubMed

    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.

  13. 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.

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

    PubMed

    Yoshida, Keisuke; Hisabori, Toru

    2016-07-01

    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

  15. Mantle redox evolution and the oxidation state of the Archean atmosphere

    NASA Technical Reports Server (NTRS)

    Kasting, J. F.; Eggler, D. H.; Raeburn, S. P.

    1993-01-01

    Current models predict that the early atmosphere consisted mostly of CO2, N2, and H2O, along with traces of H2 and CO. Such models are based on the assumption that the redox state of the upper mantle has not changed, so that volcanic gas composition has remained approximately constant with time. We argue here that this assumption is probably incorrect: the upper mantle was originally more reduced than today, although not as reduced as the metal arrest level, and has become progressively more oxidized as a consequence of the release of reduced volcanic gases and the subduction of hydrated, oxidized seafloor. Data on the redox state of sulfide and chromite inclusions in diamonds imply that the process of mantle oxidation was slow, so that reduced conditions could have prevailed for as much as half of the earth's history. To be sure, other oxybarometers of ancient rocks give different results, so the question of when the mantle redox state has changed remains unresolved. Mantle redox evolution is intimately linked to the oxidation state of the primitive atmosphere: A reduced Archean atmosphere would have had a high hydrogen escape rate and should correspond to a changing mantle redox state; an oxidized Archean atmosphere should be associated with a constant mantle redox state. The converses of these statements are also true. Finally, our theory of mantle redox evolution may explain why the Archean atmosphere remained oxygen-deficient until approximately 2.0 billion years ago (Ga) despite a probable early origin for photosynthesis.

  16. Fitness Changes in Professional Football Players During Preseason Conditioning.

    ERIC Educational Resources Information Center

    Gettman, Larry R.; And Others

    1987-01-01

    Fifty-three professional football players participated in a 14-week conditioning program prior to regular training. Seven fitness variables were measured at the beginning and at the end of the program in order to quantify changes in fitness. (Author/MT)

  17. 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...

  18. 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.

  19. 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.

  20. 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

    2015-08-01

    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). PMID:26168331

  1. Multicomponent simulations of contrasting redox environments at an LNAPL site.

    PubMed

    Miles, B; Peter, A; Teutsch, G

    2008-01-01

    A two-dimensional multicomponent reactive transport modeling approach was used to simulate contaminant transport and the evolution of redox processes at a large-scale kerosene-contaminated site near Berlin, Germany. In contrast to previous site-scale modeling studies that focused either on one or two contaminants or on steady-state redox conditions, multiple contaminants and electron acceptors, including mineral phase Iron (III), were considered with an evolving redox zonation. Inhibition terms were used to switch between the different electron acceptor processes in the reaction scheme. The transient evolution of redox zones and contaminant plumes was simulated for two separate transects of the site, which have different geology and ground water recharge distributions and where quite different downstream contaminant and terminal electron-accepting process (TEAP) distributions are observed. The same reaction system, calibrated to measured concentrations along one of the transects, was used in both cases, achieving a reasonable match with observed concentrations. The differences between the two transects could thus to some extent be attributed to the different hydrological and hydrogeological conditions, in particular ground water recharge distributions. Long-term simulations showed that the distribution of TEAPs evolves as Fe(III) becomes depleted, with conditions becoming increasingly methanogenic, leading to changes in contaminant plume lengths. The models were applied to assess the potential effects of planned changes in land use at the site that may affect the ground water recharge distribution. The simulated redox zonation responded strongly to changes in recharge, which in turn led to changes in the contaminant plume lengths.

  2. 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.

  3. Changes in complex spike activity during classical conditioning

    PubMed Central

    Rasmussen, Anders; Jirenhed, Dan-Anders; Wetmore, Daniel Z.; Hesslow, Germund

    2014-01-01

    The cerebellar cortex is necessary for adaptively timed conditioned responses (CRs) in eyeblink conditioning. During conditioning, Purkinje cells acquire pause responses or “Purkinje cell CRs” to the conditioned stimuli (CS), resulting in disinhibition of the cerebellar nuclei (CN), allowing them to activate motor nuclei that control eyeblinks. This disinhibition also causes inhibition of the inferior olive (IO), via the nucleo-olivary pathway (N-O). Activation of the IO, which relays the unconditional stimulus (US) to the cortex, elicits characteristic complex spikes in Purkinje cells. Although Purkinje cell activity, as well as stimulation of the CN, is known to influence IO activity, much remains to be learned about the way that learned changes in simple spike firing affects the IO. In the present study, we analyzed changes in simple and complex spike firing, in extracellular Purkinje cell records, from the C3 zone, in decerebrate ferrets undergoing training in a conditioning paradigm. In agreement with the N-O feedback hypothesis, acquisition resulted in a gradual decrease in complex spike activity during the conditioned stimulus, with a delay that is consistent with the long N-O latency. Also supporting the feedback hypothesis, training with a short interstimulus interval (ISI), which does not lead to acquisition of a Purkinje cell CR, did not cause a suppression of complex spike activity. In contrast, observations that extinction did not lead to a recovery in complex spike activity and the irregular patterns of simple and complex spike activity after the conditioned stimulus are less conclusive. PMID:25140129

  4. 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.

  5. 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

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

    PubMed

    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

    2015-09-14

    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.

  7. 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.

  8. 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.

  9. The CFE Treaty and changed conditions in Europe

    SciTech Connect

    Allentuck, J.

    1994-08-01

    The Treaty on Conventional Forces in Europe (CFE) was signed in November 1990 by sixteen nations, members of the North Atlantic Treaty Organization (NATO), and six nations, members of the Warsaw Treaty Organization (WTO). It was resigned to prevent a major surprise attack in Europe by the conventional forces of one Treaty Organization against those of the other and was the first major arms control treaty to address conventional weapons. This paper focuses on how CFE adapted to changes in the military-political situation in Europe which occurred after 1990 and failed to adapt to others. Suggestions are offered on how it might be changed to make it more relevant under these changed conditions.

  10. How to flip the (redox) switch.

    PubMed

    Georgiou, George

    2002-11-27

    Redox-sensitive transcription factors such as the E. coli OxyR and S. cerevisiae Yap1, are activated by conformational changes that stem from the post-translational modification of reactive protein thiols. Recent studies provide new insights on how different agents that cause redox stress mediate the activation of transcription through distinct and specific pathways. PMID:12464172

  11. 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).

  12. 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). PMID:22122251

  13. Time dependent changes in the intestinal Ca²⁺ absorption in rats with type I diabetes mellitus are associated with alterations in the intestinal redox state.

    PubMed

    Rivoira, María; Rodríguez, Valeria; López, María Peralta; Tolosa de Talamoni, Nori

    2015-03-01

    The aim was to determine the intestinal Ca²⁺ absorption in type I diabetic rats after different times of STZ induction, as well as the gene and protein expression of molecules involved in both the transcellular and paracellular Ca²⁺ pathways. The redox state and the antioxidant enzymes of the enterocytes were also evaluated in duodenum from either diabetic or insulin-treated diabetic rats as compared to control rats. Male Wistar rats (150-200 g) were divided into two groups: 1) controls and 2) STZ-induced diabetic rats (60 mg/kg b.w.). A group of diabetic rats received insulin for five days. The insulin was adjusted daily to maintain a normal blood glucose level. Five 5 d after STZ injection, there was a reduction in the intestinal Ca²⁺ absorption, which was maintained for 30 d and disappeared at 60 d. Similar changes occurred in the GSH and (˙)O(2)(-) levels. The protein expression of molecules involved in the transcellular pathway increased at 5 and 30 d returning to control values at 60 d. Their mRNA levels declined considerably at 60 d. The gene and protein expression of claudin 2 was upregulated at 30 d. Catalase activity increased at 5 and 30 d normalizing at 60 d. To conclude, type I D.m. inhibits the intestinal Ca²⁺ absorption, which is transient leading to a time dependent adaptation and returning the absorptive process to normal values. The inhibition is accompanied by oxidative stress. When insulin is administered, the duodenal redox state returns to control values and the intestinal Ca²⁺ absorption normalizes.

  14. 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

  15. [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.

  16. Zinc and the modulation of redox homeostasis

    PubMed Central

    Oteiza, Patricia I.

    2012-01-01

    Zinc, a redox inactive metal, has been long viewed as a component of the antioxidant network, and growing evidence points to its involvement in redox-regulated signaling. These actions are exerted through several mechanisms based on the unique chemical and functional properties of zinc. Overall, zinc contributes to maintain the cell redox balance through different mechanisms including: i) the regulation of oxidant production and metal-induced oxidative damage; ii) the dynamic association of zinc with sulfur in protein cysteine clusters, from which the metal can be released by nitric oxide, peroxides, oxidized glutathione and other thiol oxidant species; iii) zinc-mediated induction of the zinc-binding protein metallothionein, which releases the metal under oxidative conditions and act per se scavenging oxidants; iv) the involvement of zinc in the regulation of glutathione metabolism and of the overall protein thiol redox status; and v) a direct or indirect regulation of redox signaling. Findings of oxidative stress, altered redox signaling, and associated cell/tissue disfunction in cell and animal models of zinc deficiency, stress the relevant role of zinc in the preservation of cell redox homeostasis. However, while the participation of zinc in antioxidant protection, redox sensing, and redox-regulated signaling is accepted, the involved molecules, targets and mechanisms are still partially known and the subject of active research. PMID:22960578

  17. Klebsiella pneumoniae nitrogenase: pre-steady-state absorbance changes show that redox changes occur in the MoFe protein that depend on substrate and component protein ratio; a role for P-centres in reducing dinitrogen?

    PubMed Central

    Lowe, D J; Fisher, K; Thorneley, R N

    1993-01-01

    The pre-steady-state absorbance changes that occur during the first 0.6 s of reaction of the nitrogenase of Klebsiella pneumoniae can be simulated by associating redox changes with the different states of the MoFe protein described by our published kinetic model for nitrogenase [Lowe and Thorneley (1984) Biochem. J. 224, 877-886]. When the substrate is changed, from H+ to C2H2 (acetylene) or N2, or the nitrogenase component protein ratio is altered, these pre-steady-state absorbance changes are affected in a manner that is quantitatively predicted by our model. The results, together with parallel e.p.r. studies, are interpreted as showing that the P-clusters become oxidized when the MoFe protein is in the state where bound N2 is irreversibly committed to being reduced and is protonated to the hydrazido(2-) level. PMID:8389132

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. 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

  3. 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

    2013-11-01

    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.

  4. 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.

  5. New insights into redox control of starch degradation.

    PubMed

    Santelia, Diana; Trost, Paolo; Sparla, Francesca

    2015-06-01

    Starch is one of the major sinks of fixed carbon in photosynthetic tissues of higher plants. Carbon fixation and the synthesis of primary starch occur during the day in the chloroplast stroma, whereas starch degradation typically occurs during the following night to fuel the whole plant with energy and carbon in the absence of photosynthesis. Redox-based regulatory systems play a central role in the modulation of several chloroplastic pathways. Reversible oxidations of cysteine residues are post-translational modifications that orchestrate the precise functioning of chloroplast pathways together with changes in pH, Mg(2+) and concentrations of metabolic intermediates. Leaf starch metabolism has been intensively studied. The enzymes involved in starch synthesis and degradation have been identified and characterized. However, the redox control of the enzymes responsible for starch degradation at night remains elusive, and their response to redox transitions conflicts with the timing of the physiological events. Most of the enzymes of starch degradation are activated by reducing conditions, characteristic of daytime. Thus, redox control may have only a minor role during starch degradation at night, but could become relevant for daily stomatal opening in guard cells or in the re-allocation of fixed carbon in mesophyll cells in response to stress conditions.

  6. 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.

  7. 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

  8. 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. PMID:26809999

  9. 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

  10. 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...

  11. 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.

  12. 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

  13. Relationship between the tissue redox state potential and dak/dt changes of [K+]0 activity during k-strophantoside or acetylcholine induced contractures.

    PubMed

    Wittmann, I; Puppi, A; Dely, M

    1982-01-01

    It was established that oxidosis evoked by methylene blue during k-strophantoside and acetylcholine contractures in skeletal muscle was accompanied by an increase in the changes of [K+]0 activity, while redosis evoked by ascorbate under the same conditions was accompanied by a decrease in the changes of [K+]0 activity. These changes in [K+]0 activity parallelled the alterations of contractures caused by oxidosis or redosis suggesting that changes in the [K+]0 transient play an important role in these phenomena.

  14. Tracing changes in ecosystem function under elevated carbon dioxide conditions.

    SciTech Connect

    Pataki, D. E.; Ellsworth, D. S.; Evans, R. D.; Gonzalez-Meler, M.; King, J.; Leavitt, S. W.; Lin, G.; Matamala, R.; Pendall, E.; Siegwolf, R.; Van Kessel, C.; Ehleringer, J. F.; Environmental Research; Univ. of Utah; Univ. of Michigan; Washington State Univ.; Univ. of Illinois at Chicago; Michigan Technological Univ.; Univ. of Arizona; Columbia Univ.; Univ. of Wyoming; Paul Scherrer Inst.; Univ. of California, Davis

    2003-09-01

    Responses of ecosystems to elevated levels of atmospheric carbon dioxide (CO{sub 2}) remain a critical uncertainty in global change research. Two key unknown factors are the fate of carbon newly incorporated by photosynthesis into various pools within the ecosystem and the extent to which elevated CO{sub 2} is transferred to and sequestered in pools with long turnover times. The CO{sub 2} used for enrichment in many experiments incorporates a dual isotopic tracer, in the sense that ratios of both the stable carbon-13 ({sup 13}C) and the radioactive carbon-14 ({sup 14}C) isotopes with respect to carbon-12 are different from the corresponding ratios in atmospheric CO{sub 2}. Here we review techniques for using {sup 13}C and {sup 14}C abundances to follow the fate of newly fixed carbon and to further our understanding of the turnover times of ecosystem carbon pools. We also discuss the application of nitrogen, oxygen, and hydrogen isotope analyses for tracing changes in the linkages between carbon, nitrogen, and water cycles under conditions of elevated CO{sub 2}.

  15. Redox activity of naphthalene secondary organic aerosol

    NASA Astrophysics Data System (ADS)

    McWhinney, R. D.; Zhou, S.; Abbatt, J. P. D.

    2013-04-01

    Chamber secondary organic aerosol (SOA) from low-NOx photooxidation of naphthalene by hydroxyl radical was examined with respect to its redox cycling behaviour using the dithiothreitol (DTT) assay. Naphthalene SOA was highly redox active, consuming DTT at an average rate of 118 ± 14 pmol per minute per μg of SOA material. Measured particle-phase masses of the major previously identified redox active products, 1,2- and 1,4-naphthoquinone, accounted for only 21 ± 3% of the observed redox cycling activity. The redox-active 5-hydroxy-1,4-naphthoquinone was identified as a new minor product of naphthalene oxidation, and including this species in redox activity predictions increased the predicted DTT reactivity to 30 ± 5% of observations. Similar attempts to predict redox behaviour of oxidised two-stroke engine exhaust particles by measuring 1,2-naphthoquinone, 1,4-naphthoquinone and 9,10-phenanthrenequinone predicted DTT decay rates only 4.9 ± 2.5% of those observed. Together, these results suggest that there are substantial unidentified redox-active SOA constituents beyond the small quinones that may be important toxic components of these particles. A gas-to-SOA particle partitioning coefficient was calculated to be (7.0 ± 2.5) × 10-4 m3 μg-1 for 1,4-naphthoquinone at 25 °C. This value suggests that under typical warm conditions, 1,4-naphthoquinone is unlikely to contribute strongly to redox behaviour of ambient particles, although further work is needed to determine the potential impact under conditions such as low temperatures where partitioning to the particle is more favourable. As well, higher order oxidation products that likely account for a substantial fraction of the redox cycling capability of the naphthalene SOA are likely to partition much more strongly to the particle phase.

  16. The change in antioxidant properties of dextran-coated redox active nanoparticles due to synergetic photoreduction-oxidation.

    PubMed

    Barkam, Swetha; Das, Soumen; Saraf, Shashank; McCormack, Rameech; Richardson, David; Atencio, Leonel; Moosavifazel, Vanessa; Seal, Sudipta

    2015-09-01

    Nanoparticles have proven to be novel material with resourceful applications in the field of nanomedicine. Cerium oxide nanoparticles (CNPs) coated with dextran (Dex-CNPs) have been shown to exhibit anticancer properties which is attributed to the change in oxidation states mediated at the oxygen vacancies on the surface of CNPs. In this study, the extreme sensitivity of Dex-CNPs to visible light is demonstrated using room light with a clear indication of synergetic phenomenon of photoreduction of CNPs in the presence of dextran which undergoes simultaneous oxidation. The phenomenon was further confirmed through a systematic time-based expedited study using a high intensity visible light source. The physiochemical changes of Dex-CNPs such as dispersion stability, pH, surface chemistry, antioxidant property, cytotoxicity and the surrounding microenvironment of Dex-CNPs were significantly altered on exposure to visible light, thereby affecting the biological response. Given the significance of nanoparticles which are widely researched nanomaterials, in different fields of nanotechnology and biomedicine, this study demonstrates the significant changes in physiochemical properties of Dex-CNPs with light. The photoreduction of Dex-CNPs affects its bifunctional applications in cancer therapy and thereby this study puts forward the necessity to preserve and sustain their properties through proper storage. PMID:26190768

  17. 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. PMID:27586728

  18. 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.

  19. Redox active motifs in selenoproteins

    PubMed Central

    Li, Fei; Lutz, Patricia B.; Pepelyayeva, Yuliya; Arnér, Elias S. J.; Bayse, Craig A.; Rozovsky, Sharon

    2014-01-01

    Selenoproteins use the rare amino acid selenocysteine (Sec) to act as the first line of defense against oxidants, which are linked to aging, cancer, and neurodegenerative diseases. Many selenoproteins are oxidoreductases in which the reactive Sec is connected to a neighboring Cys and able to form a ring. These Sec-containing redox motifs govern much of the reactivity of selenoproteins. To study their fundamental properties, we have used 77Se NMR spectroscopy in concert with theoretical calculations to determine the conformational preferences and mobility of representative motifs. This use of 77Se as a probe enables the direct recording of the properties of Sec as its environment is systematically changed. We find that all motifs have several ring conformations in their oxidized state. These ring structures are most likely stabilized by weak, nonbonding interactions between the selenium and the amide carbon. To examine how the presence of selenium and ring geometric strain governs the motifs’ reactivity, we measured the redox potentials of Sec-containing motifs and their corresponding Cys-only variants. The comparisons reveal that for C-terminal motifs the redox potentials increased between 20–25 mV when the selenenylsulfide bond was changed to a disulfide bond. Changes of similar magnitude arose when we varied ring size or the motifs’ flanking residues. This suggests that the presence of Sec is not tied to unusually low redox potentials. The unique roles of selenoproteins in human health and their chemical reactivities may therefore not necessarily be explained by lower redox potentials, as has often been claimed. PMID:24769567

  20. 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.

  1. 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.

  2. Changes in menarcheal age in girls exposed to war conditions.

    PubMed

    Prebeg, Zivka; Bralic, Irena

    2000-07-01

    The purpose of this study was to assess changes in mean menarcheal age of girls in the city of Sibenik in the period from mid-1980s to the mid-1990s. Sibenik is a Dalmatian town which was exposed to hard war conditions in 1991-1995. Menarcheal status of Sibenik girls was surveyed three times, in 1981, 1985, and 1996, and included 720, 1,207, and 1,680 girls, respectively, ages 9.5-16.5 years. Mean menarcheal age was estimated by the status quo method and application of probit analysis. Results show a slight decrease in menarcheal age from 1981 to 1985 (from 12.97 +/- 0.06 years to 12.87 +/- 0.05), and then a significant increase from 12.87 +/- 0.05 years in 1985 to 13.13 +/- 0.10 years in 1996. The increase in mean menarcheal age occurred in all socioeconomic groups based on parental occupation and number of siblings. In the group of girls whose homes were damaged during war, menarche occurred at an average of 13.53 +/- 0.14 years, while those who lost a family member experienced menarche at an older mean age, 13.76 +/- 0.27 years. However, when the girls who experienced personal tragedies were excluded the onset of menarche was still later than in girls surveyed in the earlier periods. The results suggest that the general reversal in the secular trend of menarcheal age in Sibenik girls can be attributed to persistent psychological pressures and uncertainties associated with conditions of war. Am. J. Hum. Biol. 12:503-508, 2000. Copyright 2000 Wiley-Liss, Inc. PMID:11534042

  3. Changes in phosphorus smoke chemistry with environmental conditions

    SciTech Connect

    McFadden, K.M.; Ligotke, M.W.; Garland, T.R.; Van Voris, P.; Schirmer, R.E.

    1985-09-01

    Physical and chemical characteristics of two phosphorus aerosols were measured under a limited number of environmental conditions. The exposures and measurements were performed in a wind tunnel under various humidities, wind speeds and, to a limited extent, aerosol ages. Temperature, another important environmental variable that may influence the chemical form of the aerosols, was not studied in this research program. Steady-state aerosols generated by combustion of red phosphorus/butyl rubber (RP/BR) and white phosphorus (WP) were suspended in a closed-loop wind tunnel to simulate the continuous-generation of these obscurants at Army field training sites. Measured aerosol characteristics were found to differ significantly from characteristics predicted by simple phosphoric acid models previously thought to represent the chemical form of the suspended particles. As many as 28 individual phosphorus species were detected in aerosol samples. The distribution of linear and cyclic phosphorus species in the sampled aerosol was observed to vary significantly for changes in both aerosol age (0 to 60 min) and relative humidity (<5% to 90%). Hydrolysis toward phosphate occurred as the aerosol aged, and the rate of change was slower for higher humidities. More high-order phosphorus species appeared to be formed during aerosol generation at low relative humidities than at high humidity, as revealed by measurements near the combustion zone. Steady-state aerosols showed decreasing conversion to phosphate with increasing humidity. The highly speciated aerosols hydrolyzed to phosphate in less than 18 hr after deposition onto dry surfaces. Other aerosol characteristics such as mass concentration, water and phosphorus content of the particles, and particle size distribution were also measured.

  4. 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...

  5. 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

  6. Redox potentials of tungsten and its alloying partners-fundamentals of tungsten determination by redox titration.

    PubMed

    Wünsch, G

    1980-08-01

    The fundamentals of tungsten determination by redox titration in hydrochloric acid medium are describe. Conditional redox potentials are given for W, Cr, V, Fe, Ti, Mo, Cu and Sn as a function of HCl concentration. The basic experimental conditions and the difference in conditional potentials required for consecutive titrations are discussed. Any mixture of tungsten with other metals can be analysed without separation if it does not contain both Cr and Ti or both Mo and V.

  7. Differential alkylation-based redox proteomics – Lessons learnt

    PubMed Central

    Wojdyla, Katarzyna; Rogowska-Wrzesinska, Adelina

    2015-01-01

    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. PMID:26282677

  8. 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. PMID:26282677

  9. 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.

  10. Redox Processes in Silicate Melts

    NASA Astrophysics Data System (ADS)

    Cicconi, M. R.; de Ligny, D.

    2015-12-01

    Studies into the redox state of magmas provide important constrains on the formation and evolution of planetary bodies Indeed, oxygen fugacity is a key parameter in controlling the physical and chemical properties of melts and therefore it determine the possible interactions between reservoirs within the mantle and between the mantle and surface. It follows that redox mechanisms play a key role in determining the dynamics of the (inner and outer) terrestrial planets. The redox conditions that have accompanied basalt evolution on planetary bodies are known to be different, albeit with some similarities. The strongly reducing environments of the moon and meteorites have led to significant reduced mineralogical assemblages, whereas analogous terrestrial materials predominantly contain the corresponding oxidized compounds. Important geochemical elements such as Fe, Cr, V, Ce and Eu, exist in magmatic systems with different valences and coordination geometries, and the key subjects which need to be understood are: factors influencing redox mechanisms, and the effect on mineral assemblage, element partitioning, mass transfers processes and rheology of the melts. Examples on the study of Ce, Eu and Fe in silicate glasses/melts and on the parameters influencing their oxidation states will be provided.

  11. Invariance of Factors of Mouse Emotionality With Changed Experimental Conditions.

    PubMed

    Royce, J R; Poley, W

    1975-10-01

    Six factors of mouse emotionality (autonomic balance, motor discharge, acrophobia, territoriality, tunneling-1, and tunneling-2) were compared across three separate studies. Each study included 19 measures from five tests of emotionality: open field, straightaway, pole, cell, and hole-in-wall. However, conditions of testing differed significantly in each study. In the first study, the measures taken were part of a large test battery. In the second study, a reduced test battery included only the 19 measures. In the third study, this reduced battery was used again, but subjects were injected with psychoactive drugs prior to testing. In addition to these changes, different genotypes were used across studies. Subjects in the first study were tested as part of a 6 × 6 diallel table. In the second and third studies, two emotionally contrasted strains (SWR and SJL) were tested. Each population was refactored by alpha factoring with varimax, followed by promax rotations. Factors obtained were compared by quantitative means using S-index and r[SUBc] coefficients of factor matching. Although support was obtained for the invariance of all six factors, the results indicate invariance as being strongest for motor discharge and acrophobia and weakest for tunneling-1 and tunneling-2 factors.

  12. 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.

  13. Redox proteomics of fat globules unveils broad protein lactosylation and compositional changes in milk samples subjected to various technological procedures.

    PubMed

    Arena, Simona; Renzone, Giovanni; Novi, Gianfranco; Scaloni, Andrea

    2011-10-19

    The Maillard reaction between lactose and proteins occurs during thermal treatment of milk and lactosylated β-lactoglobulin, α-lactalbumin and caseins have widely been used to monitor the quality of dairy products. We recently demonstrated that a number of other whey milk proteins essential for nutrient delivery, defense against bacteria/virus and cellular proliferation become lactosylated during milk processing. The extent of their modification is associated with the harshness of product manufacturing. Since fat globule proteins are also highly important for the health-beneficial properties of milk, an evaluation of their lactosylation is crucial for a complete understanding of aliment nutritional characteristics. This is more important when milk is the unique dietary source, as in the infant diet. To this purpose, a sequential proteomic procedure involving an optimized milk fat globule (MFG) preparation/electrophoretic resolution, shot-gun analysis of gel portions for protein identification, selective trapping of lactosylated peptides by phenylboronate chromatography and their analysis by nanoLC-ESI-electron transfer dissociation (ETD) tandem MS was used for systematic characterization of fat globule proteins in milk samples subjected to various manufacturing procedures. Significant MFG protein compositional changes were observed between samples, highlighting the progressive adsorption of caseins and whey proteins on the fat globule surface as result of the technological process used. A significant lactosylation of MFG proteins was observed in ultra-high temperature sterilized and powdered for infant nutrition milk preparations, which well paralleled with the harshness of thermal treatment. Globally, this study allowed the identification of novel 157 non-redundant modification sites and 35 MFG proteins never reported so far as being lactosylated, in addition to the 153 ones ascertained here as present on other 21 MFG-adsorbed proteins whose nature was already

  14. Cerium stable isotope ratios in ferromanganese deposits and their potential as a paleo-redox proxy

    NASA Astrophysics Data System (ADS)

    Nakada, Ryoichi; Takahashi, Yoshio; Tanimizu, Masaharu

    2016-05-01

    The cerium (Ce) anomaly observed in rare earth element (REE) patterns has been used to estimate the redox state of paleo-marine environments. Cerium is unique because it forms tetravalent cations under oxic conditions, in contrast to the other REEs that occur in a trivalent state. This characteristic leads to anomalously high or low Ce concentrations relative to neighboring REEs. However, the use of Ce anomaly as a paleo-redox proxy is not well calibrated. This study shows that coupling of the Ce anomaly and Ce stable isotope ratio (δ142Ce) is more quantitative redox proxy to distinguish suboxic and oxic redox conditions. Our results revealed a progressive enrichment in heavy Ce isotopes in consecutive formations of iron (Fe) and manganese (Mn) precipitate from hot spring water without any associated change in REE patterns. The δ142Ce values of Mn precipitates were approximately 0.35‰ heavier than those of the Fe precipitates, which was consistent with experiment-based predictions. The δ142Ce values of marine ferromanganese deposits with three different formation processes were hydrogenetic (+0.25‰) > diagenetic (+0.10‰) ⩾ hydrothermal (+0.05‰), which also reflects redox conditions of their formation environment. These observations suggest that the Ce stable isotope ratios yield more quantitative information regarding redox state than REE patterns alone. We thus suggest that this novel proxy can be successfully utilized to reconstruct marine redox states, particularly from slightly oxic to highly oxic conditions such as the Great Oxidation Event (GOE).

  15. 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.

  16. Arabidopsis heat shock factor HsfA1a directly senses heat stress, pH changes, and hydrogen peroxide via the engagement of redox state.

    PubMed

    Liu, Yanfang; Zhang, Cuixian; Chen, Juan; Guo, Lihong; Li, Xiaolu; Li, Wenpeng; Yu, Zefen; Deng, Jingshi; Zhang, Pengyuan; Zhang, Keqin; Zhang, Lemin

    2013-03-01

    Arabidopsis heat shock factor HsfA1a is present in a latent, monomeric state under normal conditions; its activation involves heat stress-induced trimerization, binding to heat shock element in target promoters, and the acquisition of transcriptional competence. HsfA1a is an important regulator for heat stress-induced gene expression and thermotolerance. However, it is not clear whether HsfA1a is directly activated by stress and the mechanisms of the stress signaling are poorly understood. We analyzed HsfA1a activation by trimerization and DNA-binding assays in vitro and in vivo in response to heat stress, low/high pH, and hydrogen peroxide treatments. Our results show that purified recombinant HsfA1a was activated by these stress treatments in vitro. The same treatments also induced the binding to HSP18.2 and HSP70 promoters as examined by chromatin immunoprecipitation, and the HsfA1a DNA binding paralleled the mRNA expression of its target genes induced by different stresses. Stress-induced DNA-binding could be reversed, both in vitro and in vivo, by subsequent incubation with reducing agents (DTT, NADPH). These data suggest that HsfA1a can directly sense stress and become activated, and this process is dependent on the redox state. An N-terminal deletion of the amino acid residues from 48 to 74 negatively affected pH- and hydrogen peroxide-, but not heat-stress sensing.

  17. Timing and characterization of the change in the redox state of uranium in Precambrian surface environments: A proxy for the oxidation state of the atmosphere

    NASA Astrophysics Data System (ADS)

    Pollack, Gerald D.

    The redox-sensitive geochemical behavior of uranium permits the use of Th/U ratios as a geochemical proxy for the oxidation state of the atmosphere and oceans during sedimentary processes. Due to the effects of post-depositional uranium mobility on Th/U ratios during events involving oxygenated fluids, direct measurements of Th/U ratios are often misleading, but the whole rock Pb isotope composition may be used to determine a sample's apparent time-integrated Th/U ratio (kappaa) and the timing associated with the onset of the U-Th-Pb geochemistry. Rare earth element (REE) concentrations were determined by isotope dilution mass spectrometry to evaluate the influence of multiple provenance components and potential mobility of Th, U, and Pb during post-depositional processes on the Th/U ratio. The Pb isotope compositions and REE concentrations were determined for six Paleoproterozoic sedimentary sequences, which were the focus of previous studies involving the timing of the rise of atmospheric oxygen. The Mount McRae Shale, Huronian Supergroup, and Zaonezhskaya Formation have been interpreted as experiencing post-depositional alteration (perhaps associated with orogenic events) due to Pb-Pb ages that are younger than the likely depositional age and observed fractionation of REE in chondrite normalized REE patterns and interelement REE ratios (e.g. La/Nd, La/Yb, Eu/Eu*). Similar geochemical proxies have been interpreted as sedimentary geochemical features of the Timeball Hill Formation, Hotazel Formation, and Sengoma Argillite Formation. This study of Paleoproterozoic sedimentary units constrains the onset of U-Th decoupling, most likely due to the onset of oxidative weathering conditions, began by 2.32 Ga, the latest. Index words. Pb isotopes, Rare earth elements, Th/U ratios, Time-integrated, Atmospheric evolution, Oxygen content of the atmosphere, U-Th decoupling

  18. 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

  19. 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

  20. 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.

  1. Climate Change and Crop Exposure to Adverse Weather: Changes to Frost Risk and Grapevine Flowering Conditions

    PubMed Central

    Mosedale, Jonathan R.; Wilson, Robert J.; Maclean, Ilya M. D.

    2015-01-01

    The cultivation of grapevines in the UK and many other cool climate regions is expected to benefit from the higher growing season temperatures predicted under future climate scenarios. Yet the effects of climate change on the risk of adverse weather conditions or events at key stages of crop development are not always captured by aggregated measures of seasonal or yearly climates, or by downscaling techniques that assume climate variability will remain unchanged under future scenarios. Using fine resolution projections of future climate scenarios for south-west England and grapevine phenology models we explore how risks to cool-climate vineyard harvests vary under future climate conditions. Results indicate that the risk of adverse conditions during flowering declines under all future climate scenarios. In contrast, the risk of late spring frosts increases under many future climate projections due to advancement in the timing of budbreak. Estimates of frost risk, however, were highly sensitive to the choice of phenology model, and future frost exposure declined when budbreak was calculated using models that included a winter chill requirement for dormancy break. The lack of robust phenological models is a major source of uncertainty concerning the impacts of future climate change on the development of cool-climate viticulture in historically marginal climatic regions. PMID:26496127

  2. Climate Change and Crop Exposure to Adverse Weather: Changes to Frost Risk and Grapevine Flowering Conditions.

    PubMed

    Mosedale, Jonathan R; Wilson, Robert J; Maclean, Ilya M D

    2015-01-01

    The cultivation of grapevines in the UK and many other cool climate regions is expected to benefit from the higher growing season temperatures predicted under future climate scenarios. Yet the effects of climate change on the risk of adverse weather conditions or events at key stages of crop development are not always captured by aggregated measures of seasonal or yearly climates, or by downscaling techniques that assume climate variability will remain unchanged under future scenarios. Using fine resolution projections of future climate scenarios for south-west England and grapevine phenology models we explore how risks to cool-climate vineyard harvests vary under future climate conditions. Results indicate that the risk of adverse conditions during flowering declines under all future climate scenarios. In contrast, the risk of late spring frosts increases under many future climate projections due to advancement in the timing of budbreak. Estimates of frost risk, however, were highly sensitive to the choice of phenology model, and future frost exposure declined when budbreak was calculated using models that included a winter chill requirement for dormancy break. The lack of robust phenological models is a major source of uncertainty concerning the impacts of future climate change on the development of cool-climate viticulture in historically marginal climatic regions.

  3. [Main Cellular Redox Couples].

    PubMed

    Bilan, D S; Shokhina, A G; Lukyanov, S A; Belousov, V V

    2015-01-01

    Most of the living cells maintain the continuous flow of electrons, which provides them by energy. Many of the compounds are presented in a cell at the same time in the oxidized and reduced states, forming the active redox couples. Some of the redox couples, such as NAD+/NADH, NADP+/NADPH, oxidized/reduced glutathione (GSSG/GSH), are universal, as they participate in adjusting of many cellular reactions. Ratios of the oxidized and reduced forms of these compounds are important cellular redox parameters. Modern research approaches allow setting the new functions of the main redox couples in the complex organization of cellular processes. The following information is about the main cellular redox couples and their participation in various biological processes.

  4. 23 CFR 635.109 - Standardized changed condition clauses.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... State developed clause or clauses, however, must be in conformance with 23 U.S.C., 23 CFR and other... latent physical conditions are encountered at the site differing materially from those indicated in the contract or if unknown physical conditions of an unusual nature, differing materially from those...

  5. 23 CFR 635.109 - Standardized changed condition clauses.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... State developed clause or clauses, however, must be in conformance with 23 U.S.C., 23 CFR and other... latent physical conditions are encountered at the site differing materially from those indicated in the contract or if unknown physical conditions of an unusual nature, differing materially from those...

  6. 23 CFR 635.109 - Standardized changed condition clauses.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... State developed clause or clauses, however, must be in conformance with 23 U.S.C., 23 CFR and other... latent physical conditions are encountered at the site differing materially from those indicated in the contract or if unknown physical conditions of an unusual nature, differing materially from those...

  7. 23 CFR 635.109 - Standardized changed condition clauses.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... State developed clause or clauses, however, must be in conformance with 23 U.S.C., 23 CFR and other... latent physical conditions are encountered at the site differing materially from those indicated in the contract or if unknown physical conditions of an unusual nature, differing materially from those...

  8. 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…

  9. 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

  10. 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.

  11. 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

    2016-02-01

    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

  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. Drought-induced changes in the redox state of alpha-tocopherol, ascorbate, and the diterpene carnosic acid in chloroplasts of Labiatae species differing in carnosic acid contents.

    PubMed

    Munné-Bosch, Sergi; Alegre, Leonor

    2003-04-01

    To assess antioxidative protection by carnosic acid (CA) in combination with that of other low-molecular weight (M(r)) antioxidants (alpha-tocopherol [alpha-T] and ascorbate [Asc]) in chloroplasts, we measured endogenous concentrations of these antioxidants, their redox states, and other indicators of oxidative stress in chloroplasts of three Labiatae species, differing in their CA contents, exposed to drought stress in the field. Damage to the photosynthetic apparatus was observed neither in CA-containing species (rosemary [Rosmarinus officinalis]) and sage [Salvia officinalis]) nor in CA-free species (lemon balm [Melissa officinalis]) at relative leaf water contents between 86% and 58%, as indicated by constant maximum efficiency of photosystem II photochemistry ratios and malondialdehyde levels in chloroplasts. The three species showed significant increases in alpha-T, a shift of the redox state of alpha-T toward its reduced state, and increased Asc levels in chloroplasts under stress. Lemon balm showed the highest increases in alpha-T and Asc in chloroplasts under stress, which might compensate for the lack of CA. Besides, whereas in rosemary and sage, the redox state of CA was shifted toward its oxidized state and the redox state of Asc was kept constant, lemon balm displayed a shift of the redox state of Asc toward its oxidized state under stress. In vitro experiments showed that both CA and Asc protect alpha-T and photosynthetic membranes against oxidative damage. These results are consistent with the contention that CA, in combination with other low-M(r) antioxidants, helps to prevent oxidative damage in chloroplasts of water-stressed plants, and they show functional interdependence among different low-M(r) antioxidants in chloroplasts.

  14. 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

    2016-02-01

    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.

  15. Changing hydrological conditions in the Po basin under global warming.

    PubMed

    Coppola, Erika; Verdecchia, Marco; Giorgi, Filippo; Colaiuda, Valentina; Tomassetti, Barbara; Lombardi, Annalina

    2014-09-15

    The Po River is a crucial resource for the Italian economy, since 40% of the gross domestic product comes from this area. It is thus crucial to quantify the impact of climate change on this water resource in order to plan for future water use. In this paper a mini ensemble of 8 hydrological simulations is completed from 1960 to 2050 under the A1B emission scenario, by using the output of two regional climate models as input (REMO and RegCM) at two different resolutions (25 km-10 km and 25 km-3 km). The river discharge at the outlet point of the basin shows a change in the spring peak of the annual cycle, with a one month shift from May to April. This shift is entirely due to the change in snowmelt timing which drives most of the discharge during this period. Two other important changes are an increase of discharge in the wintertime and a decrease in the fall from September to November. The uncertainty associated with the winter change is larger compared to that in the fall. The spring shift and the fall decrease of discharge imply an extension of the hydrological dry season and thus an increase in water stress over the basin. The spatial distributions of the discharge changes are in agreement with what is observed at the outlet point and the uncertainty associated with these changes is proportional to the amplitude of the signal. The analysis of the changes in the anomaly distribution of discharge shows that both the increases and decreases in seasonal discharge are tied to the changes in the tails of the distribution, i.e. to the increase or decrease of extreme events.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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…

  1. 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.

  2. 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 ...

  3. Compromised redox homeostasis, altered nitroso–redox balance, and therapeutic possibilities in atrial fibrillation

    PubMed Central

    Simon, Jillian N.; Ziberna, Klemen; Casadei, Barbara

    2016-01-01

    Although the initiation, development, and maintenance of atrial fibrillation (AF) have been linked to alterations in myocyte redox state, the field lacks a complete understanding of the impact these changes may have on cellular signalling, atrial electrophysiology, and disease progression. Recent studies demonstrate spatiotemporal changes in reactive oxygen species production shortly after the induction of AF in animal models with an uncoupling of nitric oxide synthase activity ensuing in the presence of long-standing persistent AF, ultimately leading to a major shift in nitroso–redox balance. However, it remains unclear which radical or non-radical species are primarily involved in the underlying mechanisms of AF or which proteins are targeted for redox modification. In most instances, only free radical oxygen species have been assessed; yet evidence from the redox signalling field suggests that non-radical species are more likely to regulate cellular processes. A wider appreciation for the distinction of these species and how both species may be involved in the development and maintenance of AF could impact treatment strategies. In this review, we summarize how redox second-messenger systems are regulated and discuss the recent evidence for alterations in redox regulation in the atrial myocardium in the presence of AF, while identifying some critical missing links. We also examine studies looking at antioxidants for the prevention and treatment of AF and propose alternative redox targets that may serve as superior therapeutic options for the treatment of AF. PMID:26786158

  4. Compromised redox homeostasis, altered nitroso-redox balance, and therapeutic possibilities in atrial fibrillation.

    PubMed

    Simon, Jillian N; Ziberna, Klemen; Casadei, Barbara

    2016-04-01

    Although the initiation, development, and maintenance of atrial fibrillation (AF) have been linked to alterations in myocyte redox state, the field lacks a complete understanding of the impact these changes may have on cellular signalling, atrial electrophysiology, and disease progression. Recent studies demonstrate spatiotemporal changes in reactive oxygen species production shortly after the induction of AF in animal models with an uncoupling of nitric oxide synthase activity ensuing in the presence of long-standing persistent AF, ultimately leading to a major shift in nitroso-redox balance. However, it remains unclear which radical or non-radical species are primarily involved in the underlying mechanisms of AF or which proteins are targeted for redox modification. In most instances, only free radical oxygen species have been assessed; yet evidence from the redox signalling field suggests that non-radical species are more likely to regulate cellular processes. A wider appreciation for the distinction of these species and how both species may be involved in the development and maintenance of AF could impact treatment strategies. In this review, we summarize how redox second-messenger systems are regulated and discuss the recent evidence for alterations in redox regulation in the atrial myocardium in the presence of AF, while identifying some critical missing links. We also examine studies looking at antioxidants for the prevention and treatment of AF and propose alternative redox targets that may serve as superior therapeutic options for the treatment of AF.

  5. 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

  6. Changing Sea Ice Conditions in the Northwest Passage

    NASA Astrophysics Data System (ADS)

    Tivy, A. C.; Howell, S.; Agnew, T.; Derksen, C.

    2010-12-01

    The Northwest Passage lies in the middle of Canadian Arctic Archipelago providing a potential deepwater route that links the Atlantic and Pacific Oceans. Discovered by Sir Robert M’Clure in the 1850s, ever-present multi-year ice (MYI) has always prevented its practical navigation. 2007 marked extreme low MYI conditions in the Arctic and temporarily cleared the Northwest Passage. However, is one single clearing event within the Northwest Passage over the past 40 years indicative of future clearings? This analysis addressed two inter-related questions: i) why has the Northwest Passage contained historically heavy amounts of MYI? and ii) will decreases in MYI within the Northwest Passage continue into the future? Results indicate that for nearly 4 decades, the southern regions of the Canadian Arctic Archipelago have continuously operated as a drain-trap for MYI and this mechanism is responsible for maintaining the heavy MYI conditions within the Northwest Passage. The oldest and thickest MYI in the world resides along the northern flank of the Canadian Arctic Archipelago therefore, as the transition to a sea ice-free Arctic continues, MYI from this region will continue to migrate southward to the channels of the Northwest Passage. Results also find that 2007 was indeed an anomalously light sea ice year in the Northwest Passage but record low ice conditions have since been observed as of mid-August 2010.

  7. Dynamic Redox Regulation of IL-4 Signaling.

    PubMed

    Dwivedi, Gaurav; Gran, Margaret A; Bagchi, Pritha; Kemp, Melissa L

    2015-11-01

    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.

  8. Keap1-Nrf2 regulated redox signaling in utero: Priming of disease susceptibility in offspring.

    PubMed

    Chapple, Sarah J; Puszyk, William M; Mann, Giovanni E

    2015-11-01

    Intrauterine exposure to gestational diabetes, pre-eclampsia or intrauterine growth restriction alters the redox status of the developing fetus. Such pregnancy-related diseases in most cases do not have a readily identifiable genetic cause, and epigenetic 'priming' mechanisms in utero may predispose both mother and child to later-life onset of cardiovascular and metabolic diseases. The concept of 'fetal programing' or 'developmental priming' and its association with an increased risk of disease in childhood or adulthood has been reviewed extensively. This review focuses on adaptive changes in the in utero redox environment during normal pregnancy and the consequences of alterations in redox control associated with pregnancies characterized by oxidative stress. We evaluate the evidence that the Keap1-Nrf2 pathway is important for protecting the fetus against adverse conditions in utero and may itself be subject to epigenetic priming, potentially contributing to an increased risk of vascular disease and insulin resistance in later life. PMID:26279476

  9. Redox Species of Redox Flow Batteries: A Review.

    PubMed

    Pan, Feng; Wang, Qing

    2015-01-01

    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. PMID:26593894

  10. 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.

  11. 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.

  12. 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.

  13. Electrochemical detection for dynamic analyses of a redox component in droplets using a local redox cycling-based electrochemical (LRC-EC) chip device.

    PubMed

    Ino, Kosuke; Kanno, Yusuke; Nishijo, Taku; Goto, Takehito; Arai, Toshiharu; Takahashi, Yasufumi; Shiku, Hitoshi; Matsue, Tomokazu

    2012-09-01

    This report describes the electrochemical detection of a redox component in droplets using a local redox cycling-based electrochemical (LRC-EC) chip device consisting of 256 sensors. The time-course analyses showed that the redox compound in the droplet was dynamically changed during droplet evaporation or mass transfer through a water/oil interface.

  14. Redox regulation of the immune response.

    PubMed

    Gostner, Johanna M; Becker, Kathrin; Fuchs, Dietmar; Sucher, Robert

    2013-01-01

    Reactive oxygen and nitrogen species (ROS-RNS) and other redox active molecules fulfill key functions in immunity. Beside the initiation of cytocidal reactions within the pathogen defense strategy, redox reactions trigger and shape the immune response and are further involved in termination and initialization of cellular restorative processes. Regulatory mechanisms provided by redox-activated signaling events guarantee the correct spatial and temporal proceeding of immunological processes, and continued imbalances in redox homeostasis lead to crucial failures of control mechanisms, thus promoting the development of pathological conditions. Interferon-gamma is the most potent inducer of ROS-RNS formation in target cells like macrophages. Immune-regulatory pathways such as tryptophan breakdown via indoleamine 2,3-dioxygenase and neopterin production by GTP-cyclohydrolase-I are initiated during T helper cell type 1 (Th1-type) immune response concomitant to the production of ROS-RNS by immunocompetent cells. Therefore, increased neopterin production and tryptophan breakdown is representative of an activated cellular immune system and can be used for the in vivo and in vitro monitoring of oxidative stress. In parallel, the activation of the redox-sensitive transcription factor nuclear factor-kappa B is a central element in immunity leading to cell type and stimulus-specific expression of responsive genes. Furthermore, T cell activation and proliferation are strongly dependent on the redox potential of the extracellular microenvironment. T cell commitment to Th1, Th2, regulatory T cell, and other phenotypes appears to crucially depend on the activation of redox-sensitive signaling cascades, where oxidative conditions support Th1 development while 'antioxidative' stress leads to a shift to allergic Th2-type immune responses.

  15. 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

  16. 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.

  17. Intracellular Redox Compartmentation and ROS-Related Communication in Regulation and Signaling.

    PubMed

    Noctor, Graham; Foyer, Christine H

    2016-07-01

    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

  18. Redox- and Reactive Oxygen Species-Dependent Signaling into and out of the Photosynthesizing Chloroplast.

    PubMed

    Dietz, Karl-Josef; Turkan, Ismail; Krieger-Liszkay, Anja

    2016-07-01

    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

  19. 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

  20. Thiol-Based Redox Switches and Gene Regulation

    PubMed Central

    2011-01-01

    Abstract Cysteine is notable among the universal, proteinogenic amino acids for its facile redox chemistry. Cysteine thiolates are readily modified by reactive oxygen species (ROS), reactive electrophilic species (RES), and reactive nitrogen species (RNS). Although thiol switches are commonly triggered by disulfide bond formation, they can also be controlled by S-thiolation, S-alkylation, or modification by RNS. Thiol-based switches are common in both prokaryotic and eukaryotic organisms and activate functions that detoxify reactive species and restore thiol homeostasis while repressing functions that would be deleterious if expressed under oxidizing conditions. Here, we provide an overview of the best-understood examples of thiol-based redox switches that affect gene expression. Intra- or intermolecular disulfide bond formation serves as a direct regulatory switch for several bacterial transcription factors (OxyR, OhrR/2-Cys, Spx, YodB, CrtJ, and CprK) and indirectly regulates others (the RsrA anti-σ factor and RegB sensory histidine kinase). In eukaryotes, thiol-based switches control the yeast Yap1p transcription factor, the Nrf2/Keap1 electrophile and oxidative stress response, and the Chlamydomonas NAB1 translational repressor. Collectively, these regulators reveal a remarkable range of chemical modifications exploited by Cys residues to effect changes in gene expression. Antioxid. Redox Signal. 14, 1049—1063. PMID:20626317

  1. Chloroplastic thioredoxin-f and thioredoxin-m1/4 play important roles in brassinosteroids-induced changes in CO2 assimilation and cellular redox homeostasis in tomato.

    PubMed

    Cheng, Fei; Zhou, Yan-Hong; Xia, Xiao-Jian; Shi, Kai; Zhou, Jie; Yu, Jing-Quan

    2014-08-01

    Chloroplast thioredoxins (TRXs) and glutathione function as redox messengers in the regulation of photosynthesis. In this work, the roles of chloroplast TRXs in brassinosteroids (BRs)-induced changes in cellular redox homeostasis and CO2 assimilation were studied in the leaves of tomato plants. BRs-deficient d (^im) plants showed decreased transcripts of TRX-f, TRX-m2, TRX-m1/4, and TRX-x, while exogenous BRs significantly induced CO2 assimilation and the expression of TRX-f, TRX-m2, TRX-m1/4, and TRX-x. Virus-induced gene silencing (VIGS) of the chloroplast TRX-f, TRX-m2, TRX-m1/4, and TRX-y genes individually increased membrane lipid peroxidation and accumulation of 2-Cys peroxiredoxin dimers, and decreased the activities of the ascorbate-glutathione cycle enzymes and the ratio of reduced glutathione to oxidized glutathione (GSH/GSSG) in the leaves. Furthermore, partial silencing of TRX-f, TRX-m2, TRX-m1/4, and TRX-y resulted in decreased expression of genes involved in the Benson-Calvin cycle and decreased activity of the associated enzymes. Importantly, the BRs-induced increase in CO2 assimilation and the increased expression and activities of antioxidant- and photosynthesis-related genes and enzymes were compromised in the partially TRX-f- and TRX-m1/4-silenced plants. All of these results suggest that TRX-f and TRX-m1/4 are involved in the BRs-induced changes in CO2 assimilation and cellular redox homeostasis in tomato.

  2. Chloroplastic thioredoxin-f and thioredoxin-m1/4 play important roles in brassinosteroids-induced changes in CO2 assimilation and cellular redox homeostasis in tomato

    PubMed Central

    Cheng, Fei; Zhou, Yan-Hong; Xia, Xiao-Jian; Shi, Kai; Zhou, Jie; Yu, Jing-Quan

    2014-01-01

    Chloroplast thioredoxins (TRXs) and glutathione function as redox messengers in the regulation of photosynthesis. In this work, the roles of chloroplast TRXs in brassinosteroids (BRs)-induced changes in cellular redox homeostasis and CO2 assimilation were studied in the leaves of tomato plants. BRs-deficient d ^im plants showed decreased transcripts of TRX-f, TRX-m2, TRX-m1/4, and TRX-x, while exogenous BRs significantly induced CO2 assimilation and the expression of TRX-f, TRX-m2, TRX-m1/4, and TRX-x. Virus-induced gene silencing (VIGS) of the chloroplast TRX-f, TRX-m2, TRX-m1/4, and TRX-y genes individually increased membrane lipid peroxidation and accumulation of 2-Cys peroxiredoxin dimers, and decreased the activities of the ascorbate–glutathione cycle enzymes and the ratio of reduced glutathione to oxidized glutathione (GSH/GSSG) in the leaves. Furthermore, partial silencing of TRX-f, TRX-m2, TRX-m1/4, and TRX-y resulted in decreased expression of genes involved in the Benson–Calvin cycle and decreased activity of the associated enzymes. Importantly, the BRs-induced increase in CO2 assimilation and the increased expression and activities of antioxidant- and photosynthesis-related genes and enzymes were compromised in the partially TRX-f- and TRX-m1/4-silenced plants. All of these results suggest that TRX-f and TRX-m1/4 are involved in the BRs-induced changes in CO2 assimilation and cellular redox homeostasis in tomato. PMID:24847092

  3. 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.

  4. Identification of Early Nuclear Target Genes of Plastidial Redox Signals that Trigger the Long-Term Response of Arabidopsis to Light Quality Shifts.

    PubMed

    Dietzel, Lars; Gläßer, Christine; Liebers, Monique; Hiekel, Stefan; Courtois, Florence; Czarnecki, Olaf; Schlicke, Hagen; Zubo, Yan; Börner, Thomas; Mayer, Klaus; Grimm, Bernhard; Pfannschmidt, Thomas

    2015-08-01

    Natural illumination conditions are highly variable and because of their sessile life style, plants are forced to acclimate to them at the cellular and molecular level. Changes in light intensity or quality induce changes in the reduction/oxidation (redox) state of the photosynthetic electron chain that acts as a trigger for compensatory acclimation responses comprising functional and structural adjustments of photosynthesis and metabolism. Such responses include redox-controlled changes in plant gene expression in the nucleus and organelles. Here we describe a strategy for the identification of early redox-regulated genes (ERGs) in the nucleus of the model organism Arabidopsis thaliana that respond significantly 30 or 60 min after the generation of a reduction signal in the photosynthetic electron transport chain. By comparing the response of wild-type plants with that of the acclimation mutant stn7, we could specifically identify ERGs. The results reveal a significant impact of chloroplast redox signals on distinct nuclear gene groups including genes for the mitochondrial electron transport chain, tetrapyrrole biosynthesis, carbohydrate metabolism, and signaling lipid synthesis. These expression profiles are clearly different from those observed in response to the reduction of photosynthetic electron transport by high light treatments. Thus, the ERGs identified are unique to redox imbalances in photosynthetic electron transport and were then used for analyzing potential redox-responsive cis-elements, trans-factors, and chromosomal regulatory hot spots. The data identify a novel redox-responsive element and indicate extensive redox control at transcriptional and chromosomal levels that point to an unprecedented impact of redox signals on epigenetic processes.

  5. 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

  6. 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).

  7. 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. PMID:23089153

  8. 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.

  9. Tracer test with As(V) under variable redox conditions controlling arsenic transport in the presence of elevated ferrous iron concentrations.

    PubMed

    Höhn, R; Isenbeck-Schröter, M; Kent, D B; Davis, J A; Jakobsen, R; Jann, S; Niedan, V; Scholz, C; Stadler, S; Tretner, A

    2006-11-20

    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 muM) 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. PMID:16945450

  10. 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

  11. 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, Weijun; 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.

  12. Redox-based epigenetic status in drug addiction: a potential contributor to gene priming and a mechanistic rationale for metabolic intervention

    PubMed Central

    Trivedi, Malav S.; Deth, Richard

    2015-01-01

    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. PMID:25657617

  13. Electronegativity and redox reactions.

    PubMed

    Miranda-Quintana, Ramón Alain; Martínez González, Marco; Ayers, Paul W

    2016-08-10

    Using the maximum hardness principle, we show that the oxidation potential of a molecule increases as its electronegativity increases and also increases as its electronegativity in its oxidized state increases. This insight can be used to construct a linear free energy relation for the oxidation potential, which we train on a set of 31 organic redox couples and test on a set of 10 different redox reactions. Better results are obtained when the electronegativity of the oxidized/reduced reagents are adjusted to account for the reagents' interaction with their chemical environment.

  14. 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.

  15. Marine redox conditions in the middle Proterozoic ocean and isotopic constraints on authigenic carbonate formation: Insights from the Chuanlinggou Formation, Yanshan Basin, North China

    NASA Astrophysics Data System (ADS)

    Li, Chao; Planavsky, Noah J.; Love, Gordon D.; Reinhard, Christopher T.; Hardisty, Dalton; Feng, Lianjun; Bates, Steven M.; Huang, Jing; Zhang, Qirui; Chu, Xuelei; Lyons, Timothy W.

    2015-02-01

    To improve our understanding of ocean chemistry and biogeochemical cycling following the termination of large-scale Paleoproterozoic iron formation (IF) deposition (∼1.85 billion years ago [Ga]), we conducted a Fe-S-C-Mo geochemical study of the ∼1.65 Ga Chuanlinggou Formation, Yanshan Basin, North China. Despite the cessation of IF deposition, our results suggest the presence of anoxic but non-euxinic (ferruginous) conditions persisted below the surface mixed layer for the deepest portion of the continental rifting basin and that this pattern is apparently independent of the local organic carbon content. However, our paired S-isotope data of carbonate-associated sulfate and pyrite suggest presence of sulfate in pore fluids, which is not consistent with insufficient sulfate for bacterial sulfate reduction in the water column. Despite evidence for deposition under anoxic conditions, sedimentary molybdenum (Mo) concentrations are mostly not enriched relative to average continental crust. This relationship is consistent with the notion that sulfide-dominated conditions in the water column and/or the sediments are required for Mo enrichment and validates past assertions that Mo enrichment patterns in ancient shales track both the local presence and global distribution of euxinia specifically. In addition, we identified extensive diagenetic carbonate precipitation in the upper Chuanlinggou Formation with only moderately negative δ13C values (-3.4 ± 1.4‰). We propose, with support from a numerical model, that these diagenetic carbon isotope values were most likely derived from precipitation of carbonates dominantly in the methanic zone within the sediments. Diagenetic carbonate precipitation in the methanic zone is likely to have been more extensive in the Proterozoic than the Phanerozoic due to porewater oxidant limitation.

  16. 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

  17. 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

  18. 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

  19. 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

    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

  20. 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

    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.

  1. Perceptual Consequences of Changes in Vocoded Speech Parameters in Various Reverberation Conditions

    ERIC Educational Resources Information Center

    Drgas, Szymon; Blaszak, Magdalena A.

    2009-01-01

    Purpose: To study the perceptual consequences of changes in parameters of vocoded speech in various reverberation conditions. Method: The 3 controlled variables were number of vocoder bands, instantaneous frequency change rate, and reverberation conditions. The effects were quantified in terms of (a) nonsense words' recognition scores for young…

  2. 30 CFR 203.77 - May I voluntarily give up relief if conditions change?

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 2 2012-07-01 2012-07-01 false May I voluntarily give up relief if conditions change? 203.77 Section 203.77 Mineral Resources BUREAU OF SAFETY AND ENVIRONMENTAL ENFORCEMENT... Sulfur General § 203.77 May I voluntarily give up relief if conditions change? Yes, you may...

  3. 30 CFR 203.77 - May I voluntarily give up relief if conditions change?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 2 2010-07-01 2010-07-01 false May I voluntarily give up relief if conditions change? 203.77 Section 203.77 Mineral Resources MINERALS MANAGEMENT SERVICE, DEPARTMENT OF THE INTERIOR... voluntarily give up relief if conditions change? Yes, you may voluntarily give up relief by sending a...

  4. 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

  5. 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. PMID:26351797

  6. 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.

  7. 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. PMID:21625550

  8. 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…

  9. Fear conditioning-related changes in cerebellar Purkinje cell activities in goldfish

    PubMed Central

    2012-01-01

    Background Fear conditioning-induced changes in cerebellar Purkinje cell responses to a conditioned stimulus have been reported in rabbits. It has been suggested that synaptic long-term potentiation and the resulting increases in firing rates of Purkinje cells are related to the acquisition of conditioned fear in mammals. However, Purkinje cell activities during acquisition of conditioned fear have not been analysed, and changes in Purkinje cell activities throughout the development of conditioned fear have not yet been investigated. In the present study, we tracked Purkinje cell activities throughout a fear conditioning procedure and aimed to elucidate further how cerebellar circuits function during the acquisition and expression of conditioned fear. Methods Activities of single Purkinje cells in the corpus cerebelli were tracked throughout a classical fear conditioning procedure in goldfish. A delayed conditioning paradigm was used with cardiac deceleration as the conditioned response. Conditioning-related changes of Purkinje cell responses to a conditioned stimulus and unconditioned stimulus were examined. Results The majority of Purkinje cells sampled responded to the conditioned stimulus by either increasing or decreasing their firing rates before training. Although there were various types of conditioning-related changes in Purkinje cells, more than half of the cells showed suppressed activities in response to the conditioned stimulus after acquisition of conditioned fear. Purkinje cells that showed unconditioned stimulus-coupled complex-spike firings also exhibited conditioning-related suppression of simple-spike responses to the conditioned stimulus. A small number of Purkinje cells showed increased excitatory responses in the acquisition sessions. We found that the magnitudes of changes in the firing frequencies of some Purkinje cells in response to the conditioned stimulus correlated with the magnitudes of the conditioned responses on a trial

  10. 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.

  11. Redox regulation of protein damage in plasma

    PubMed Central

    Griffiths, Helen R.; Dias, Irundika H.K.; Willetts, Rachel S.; Devitt, Andrew

    2014-01-01

    The presence and concentrations of modified proteins circulating in plasma depend on rates of protein synthesis, modification and clearance. In early studies, the proteins most frequently analysed for damage were those which were more abundant in plasma (e.g. albumin and immunoglobulins) which exist at up to 10 orders of magnitude higher concentrations than other plasma proteins e.g. cytokines. However, advances in analytical techniques using mass spectrometry and immuno-affinity purification methods, have facilitated analysis of less abundant, modified proteins and the nature of modifications at specific sites is now being characterised. The damaging reactive species that cause protein modifications in plasma principally arise from reactive oxygen species (ROS) produced by NADPH oxidases (NOX), nitric oxide synthases (NOS) and oxygenase activities; reactive nitrogen species (RNS) from myeloperoxidase (MPO) and NOS activities; and hypochlorous acid from MPO. Secondary damage to proteins may be caused by oxidized lipids and glucose autooxidation. In this review, we focus on redox regulatory control of those enzymes and processes which control protein maturation during synthesis, produce reactive species, repair and remove damaged plasma proteins. We have highlighted the potential for alterations in the extracellular redox compartment to regulate intracellular redox state and, conversely, for intracellular oxidative stress to alter the cellular secretome and composition of extracellular vesicles. Through secreted, redox-active regulatory molecules, changes in redox state may be transmitted to distant sites. PMID:24624332

  12. 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.

  13. 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…

  14. 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.

  15. Redox proteomics for the assessment of redox-related posttranslational regulation in plants.

    PubMed

    Mock, Hans-Peter; Dietz, Karl-Josef

    2016-08-01

    The methodological developments of in vivo and in vitro protein labeling and subsequent detection enable sensitive and specific detection of redox modifications. Such methods are presently applied to diverse cells and tissues, subproteomes and developmental as well as environmental conditions. The chloroplast proteome is particularly suitable for such kind of studies, because redox regulation of chloroplast proteins is well established, many plastid proteins are abundant, redox network components have been inventoried in great depth, and functional consequences explored. Thus the repertoire of redox-related posttranslational modifications on the one hand side and their abundance on the other pose a challenge for the near future to understand their contribution to physiological regulation. The various posttranslational redox modifications are introduced, followed by a description of the available proteomics methods. The significance of the redox-related posttranslational modification is exemplarily worked out using established examples from photosynthesis. This article is part of a Special Issue entitled: Plant Proteomics--a bridge between fundamental processes and crop production, edited by Dr. Hans-Peter Mock.

  16. N-substituted phenothiazines as redox indicators in titrations with chloramine-T and chloramine-B.

    PubMed

    Gowda, H S; Mohan, B M; Ahmed, S A

    1980-12-01

    Profenamine hydrochloride, fluphenazine dihydrochloride, trifluopromazine hydrochloride, cyamepromazine maleate, perphenazine dihydrochloride and mepazine hydrochloride are proposed as redox indicators in the titration of hydroquinone, metol and ascorbic acid with chloramine-T and chloramine-B in sulphuric, hydrochloric and acetic acid media. They give a sharp reversible colour change at the equivalence point. A simple but accurate method for the determination of hydroquinone, metol and ascorbic acid is described. The conditional potentials and molar absorptivities of the indicators and redox potential of chloramine-B are reported.

  17. Controlling Scattering Instabilities and Adapting to Unknown and Changing Plasma Conditions Using STUD Pulses

    NASA Astrophysics Data System (ADS)

    Afeyan, Bedros; Hüller, Stefan

    2012-10-01

    We will show the results of changing STUD pulse configurations in order to maintain strict control of parametric instabilities in high energy density plasmas (HEDP). Nonlinear optical processes (NLOP) in HEDP respond to changing plasma conditions which are unknown and not easily knowable by standard experimental procedures. Adapting to changing and unknown plasma conditions is one feature of STUD pulses which is absent in other beam conditioning techniques. We demonstrate this by simulating long enough that plasma conditions change, instability gains are altered and new STUD pulse configurations become necessary. Two such configurations are spliced together or run independently and compared. All available methods of changing STUD pulse characteristics are explored, such as duty cycle (20% vs 50%) and modulation period (cutting hot spots in half and into quarters) as well as phase scrambling and number of spikes before the spatial distribution of hot spots is randomized (1, 2, 3 and infinity).

  18. The Importance of Redox Reactions in Fluid Transport Systems in the Earth's Deep Mantle: Evidence from Nano-Inclusions

    NASA Astrophysics Data System (ADS)

    Jacob, D. E.; Wirth, R.; Dobrzhinetskaya, L.

    2014-12-01

    Focused Ion beam assisted TEM studies of inclusions in diamond have opened up a new perspective on the Earth's deep mantle processes. They enabled direct observation of fluids and have shown a large chemical and redox heterogeneity at the submicron scale, which is not observed in micron-sized inclusions. While crustal metamorphic diamonds are generally formed under oxidizing conditions, polycrystalline diamonds from the Earth's mantle and carbonado have inclusion suites reflecting variable, and sometimes extreme, redox conditions. Diamond fluid compositions, however, fall in the same compositional field for worldwide diamond fluids, regardless of their geodynamic environment. They conform with the fluid end-members established by studies on fibrous diamonds, suggesting a universally important role of a limited number of basic ingredients, namely carbonates, silicates, halides and water. Strong redox gradients reflected by the micro-inclusions indicate diamond precipitation via small-scale, ephemeral redox processes driven by the contrasting oxidation states of fluids and their depositional environment. The susceptibility of the melting point of mantle rocks to the presence of even small amounts of volatiles promotes melting simultaneous to diamond precipitation, which is further enhanced by the changing of fluid composition towards higher water activity. This creates a chemically heterogeneous environment, in which diamonds and their inclusions are precipitated via redox-freezing processes.

  19. 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. PMID:24623849

  20. 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

  1. 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

  2. Relationship between developmental synaptic modulation and conditioning-induced synaptic change in Lymnaea.

    PubMed

    Karasawa, T; Sato, Nao; Horikoshi, T; Sakakibara, M

    2008-01-01

    Though adult Lymnaea are bimodal breathers, young animals breathe mainly through the skin and adults through the lung. Operant conditioning changes adult breathing behavior from aerial to cutaneous. We hypothesized that this behavioral change is caused by alterations in the neuronal circuit during both development and conditioning. We focused our study on whether the synaptic connection between RPeD1 and RPA6 neurons is modulated during development and conditioning. Our findings indicated that the RPeD1 has an excitatory monosynaptic contact with the RPA6 in young naive and operantly-conditioned adult animals. The relationship of this contact was well correlated with their respiratory behavior.

  3. 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

    2014-01-01

    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.

  4. 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

  5. Microfluidic redox battery.

    PubMed

    Lee, Jin Wook; Goulet, Marc-Antoni; Kjeang, Erik

    2013-07-01

    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. PMID:23712370

  6. Microfluidic redox battery.

    PubMed

    Lee, Jin Wook; Goulet, Marc-Antoni; Kjeang, Erik

    2013-07-01

    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.

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. Changes in membrane currents during Pavlovian conditioning of single cortical neurons.

    PubMed

    Woody, C D; Gruen, E; Birt, D

    1991-01-18

    Single electrode voltage clamp recordings were made during Pavlovian conditioning of single units of the motor cortex of cats. Units that developed a conditioned spike discharge in response to a click conditioned stimulus (CS) after pairing the click with glabella tap and local ionophoretic application of glutamate showed increases in input resistance and reductions of an early outward current induced by depolarizing commands and by return to holding potentials after hyperpolarizing commands. Changes in later currents were also found in some cells. Units that failed to develop a conditioned response did not show these changes. The decreases in membrane currents could contribute to an increased spike discharge in response to the CS as could the increased input resistance observed after conditioning. Conductance changes of this type may serve as engrams by which some forms of memory and learning are expressed across both vertebrate and invertebrate species.

  12. 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.

  13. 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.

  14. Corrosion fatigue behavior and life prediction method under changing temperature condition

    SciTech Connect

    Kanasaki, Hiroshi; Hirano, Akihiko; Iida, Kunihiro; Asada, Yasuhide

    1997-12-01

    Axially strain controlled low cycle fatigue tests of a carbon steel in oxygenated high temperature water were carried out under changing temperature conditions. Two patterns of triangular wave were selected for temperature cycling. One was in-phase pattern synchronizing with strain cycling and the other was an out-of-phase pattern in which temperature was changed in anti-phase to the strain cycling. The fatigue life under changing temperature condition was in the range of the fatigue life under various constant temperature within the range of the changing temperature. The fatigue life of in-phase pattern was equivalent to that of out-of-phase pattern. The corrosion fatigue life prediction method was proposed for changing temperature condition, and was based on the assumption that the fatigue damage increased in linear proportion to increment of strain during cycling. The fatigue life predicted by this method was in good agreement with the test results.

  15. Connexin and Pannexin hemichannels are regulated by redox potential.

    PubMed

    Retamal, Mauricio A

    2014-01-01

    Connexins (Cxs) and Pannexins (Panxs) are two non-related protein families, having both the property to form hemichannels at the plasma membrane. There are 21 genes coding for different Cx based proteins and only 3 for Panx. Under physiological conditions, these hemichannels (Cxs and Panxs) present a low open probability, but when open, they allow the release of signaling molecules to the extracellular space. However, under pathological conditions, these hemichannels increase their open probability, inducing important lysis of metabolites, and ionic imbalance, which in turn induce the massive entry of Ca(+2) to the cell. Actually, it is well recognized that Cxs and Panxs based channels play an important role in several diseases and -in many cases- this is associated with an aberrant hemichannel opening. Hemichannel opening and closing ar