Science.gov

Sample records for content redox potential

  1. [Effects of water content on redox potential and carbon mineralization of wetland sediments].

    PubMed

    Yang, Gai-ren; Tong, Cheng-li; Xiao, He-ai; Wu, Jin-shui

    2009-08-15

    To better understand the effect of soil water contents on redox potential (Eh), and their impacts on C mineralization in natural wetland, sediment samples from 3 types of wetlands (fen, humus marsh and marshy meadow) in the San-jiang Plate region of North China were incubated (25 degrees C) for 155 d under a range of reducing and oxidizing conditions by controlling water contents (varied from 24% to 232% of water holding capacity) (WHC). CO2-C evolved during incubation was measured at different time intervals. Results showed that Eh of sediments decreased significantly as water content increased from 24% WHC (lighted moisturized) to about 100% WHC, then decreased slightly as water content increased further to a level of submersed (about 2 cm water-depths). The accumulative amount of CO2-C evolved from the sediments indicated that the optimum water contents for mineralization of organic C are 32%, 48% and 76%-100% WHC for sediments of fen, humus marsh, and marshy meadow, respectively. The relationship between mineralization rates and redox potentials (Eh) were well fitted with second order parabola equations (p < 0.05). Mineralization rates and accumulative amount of organic C displayed a positive correlation with Eh up to 300 mV. However, a significant negative correlation was observed when Eh increased above 300 mV. Results demonstrated that low redox potential is the controlling factor of carbon accumulation of wetland in San-jiang Plate region.

  2. Measurement of Redox Potential in Nanoecotoxicological Investigations

    PubMed Central

    Tantra, Ratna; Cackett, Alex; Peck, Roger; Gohil, Dipak; Snowden, Jacqueline

    2012-01-01

    Redox potential has been identified by the Organisation for Economic Co-operation and Development (OECD) as one of the parameters that should be investigated for the testing of manufactured nanomaterials. There is still some ambiguity concerning this parameter, i.e., as to what and how to measure, particularly when in a nanoecotoxicological context. In this study the redox potentials of six nanomaterials (either zinc oxide (ZnO) or cerium oxide (CeO2)) dispersions were measured using an oxidation-reduction potential (ORP) electrode probe. The particles under testing differed in terms of their particle size and dispersion stability in deionised water and in various ecotox media. The ORP values of the various dispersions and how they fluctuate relative to each other are discussed. Results show that the ORP values are mainly governed by the type of liquid media employed, with little contributions from the nanoparticles. Seawater was shown to have reduced the ORP value, which was attributed to an increase in the concentration of reducing agents such as sulphites or the reduction of dissolved oxygen concentration. The lack of redox potential value contribution from the particles themselves is thought to be due to insufficient interaction of the particles at the Pt electrode of the ORP probe. PMID:22131988

  3. Organic Redox Species in Aqueous Flow Batteries: Redox Potentials, Chemical Stability and Solubility

    PubMed Central

    Wedege, Kristina; Dražević, Emil; Konya, Denes; Bentien, Anders

    2016-01-01

    Organic molecules are currently investigated as redox species for aqueous low-cost redox flow batteries (RFBs). The envisioned features of using organic redox species are low cost and increased flexibility with respect to tailoring redox potential and solubility from molecular engineering of side groups on the organic redox-active species. In this paper 33, mainly quinone-based, compounds are studied experimentially in terms of pH dependent redox potential, solubility and stability, combined with single cell battery RFB tests on selected redox pairs. Data shows that both the solubility and redox potential are determined by the position of the side groups and only to a small extent by the number of side groups. Additionally, the chemical stability and possible degradation mechanisms leading to capacity loss over time are discussed. The main challenge for the development of all-organic RFBs is to identify a redox pair for the positive side with sufficiently high stability and redox potential that enables battery cell potentials above 1 V. PMID:27966605

  4. Organic Redox Species in Aqueous Flow Batteries: Redox Potentials, Chemical Stability and Solubility

    NASA Astrophysics Data System (ADS)

    Wedege, Kristina; Dražević, Emil; Konya, Denes; Bentien, Anders

    2016-12-01

    Organic molecules are currently investigated as redox species for aqueous low-cost redox flow batteries (RFBs). The envisioned features of using organic redox species are low cost and increased flexibility with respect to tailoring redox potential and solubility from molecular engineering of side groups on the organic redox-active species. In this paper 33, mainly quinone-based, compounds are studied experimentially in terms of pH dependent redox potential, solubility and stability, combined with single cell battery RFB tests on selected redox pairs. Data shows that both the solubility and redox potential are determined by the position of the side groups and only to a small extent by the number of side groups. Additionally, the chemical stability and possible degradation mechanisms leading to capacity loss over time are discussed. The main challenge for the development of all-organic RFBs is to identify a redox pair for the positive side with sufficiently high stability and redox potential that enables battery cell potentials above 1 V.

  5. Redox potentials in ammonium nitrate solutions

    SciTech Connect

    Ngameni, E.; Ammaa, B.B.; Wandji, R.; Bessiere, J.

    1995-03-01

    The redox potentials of M{sup n+}/M (M{sup n+} = Cu{sup 2+}, Pb{sup 2+}, Sn{sup 2+}, Cd{sup 2+}, Ag{sup +}, Zn{sup 2+}, Hg{sup 2+}), M{sup n+}/M {sup (n{minus}m)+} (Fe{sup 3+}/Fe{sup 2+}, Fe(CN){sub 6}3{minus}/Fe(CN){sub 6}{sup 4{minus}}), and AgX/Ag, X{sup {minus}} (X = Cl, Br, and I) have been measured in aqueous solutions of ammonium nitrate (1--14 M). The variation of salvation of ions, characterized by the solvent transfer coefficient f{sup tr}, is calculated from the normal redox potentials of the systems. For all the cases, the potential of the ferricinium/ferrocene system (Fe{sup +}/Fc) is used as a reference of potential. It appears as a general trend that when the concentration of salt increases from 1 to 14 M, the potentials of the systems vary slightly, indicating weak interactions between these solutes and the salt. The examined ions can be classified into two groups: those that are less solvated as the concentration of NH{sub 4}NO{sub 3} increases (CU{sup 2+}, Cd{sup 2+}, Zn{sup 2+}, Cl{sup {minus}}, Br{sup {minus}}, I{sup {minus}}) and those that are more solvated, (Pb{sup 2+}, Ag{sup +}, Hg{sup 2+}, Sn{sup 2+}). The solubility constants of the AgX salts in the H{sub 2}O + NH{sub 4}NO{sub 3} mixtures are also calculated.

  6. [Determination of the redox potential of water saturated with hydrogen].

    PubMed

    Piskarev, I M; Ushkanov, V A; Aristova, N A; Likhachev, P P; Myslivets, T C

    2010-01-01

    It has been shown that the redox potential of water saturated with hydrogen is -500--700 mV. The time of the establishment of the potential is 24 h. The potential somewhat increases with increasing volume of hydrogen introduced to a reservoir with water and practically does not depend on the presence of additions in water, provided these additions are not reduced by hydrogen. The pH value of water does not change after the addition of water. In a glass vessel with a metallic cover resting on the side, no decrease in potential during the 2.5-month storage was observed. In plastic bottles, the content of hydrogen decreased; on storage for more than two weeks, it disappeared almost completely, and as a result, the potential increased after storage for three to four weeks to a level near zero. In an open vessel, the potential remained negative for two days.

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

    DTIC Science & Technology

    1990-08-01

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

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

    PubMed

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

    1996-09-17

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

  9. Redox equilibria of iron oxides in aqueous-based magnetite dispersions: effect of pH and redox potential.

    PubMed

    Pang, Suh Cem; Chin, Suk Fun; Anderson, Marc A

    2007-07-01

    The effect of pH and redox potential on the redox equilibria of iron oxides in aqueous-based magnetite dispersions was investigated. The ionic activities of each dissolved iron species in equilibrium with magnetite nanoparticles were determined and contoured within the Eh-pH framework of a composite stability diagram. Both standard redox potentials and equilibrium constants for all major iron oxide redox equilibria in magnetite dispersions were found to differ from values reported for noncolloidal systems. The "triple point" position of redox equilibrium among Fe(II) ions, magnetite, and hematite shifted to a higher standard redox potential and an equilibrium constant which was several orders of magnitude higher. The predominant area of magnetite stability was enlarged to cover a wider range of both pH and redox potentials as compared to that of a noncolloidal magnetite system.

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

    NASA Astrophysics Data System (ADS)

    Sajedi, Toktam; Prescott, Cindy; Lavkulich, Les

    2010-05-01

    Redox potential (Eh) is an integrated soil measurement that reflects several environmental conditions in the soil associated with aeration, moisture and carbon (organic matter) dynamics. Its measurement can be related to water table fluctuations, precipitation and landscape gradients, organic matter decomposition rates, nutrient dynamics, biological diversity and plant species distribution. Redox is an excellent indicator of soil biological processes, as it is largely a reflection of microbial activities which to a large extent govern carbon dynamics and nutrient cycling. Redox thus serves as an ecological indicator of site productivity at the ecosystem scale and may be used for management purposes as its magnitude can be altered by activities such as harvesting and drainage. A threshold value of 300 mv has been documented as the critical value below which anaerobic conditions in the soil develop. However, redox measurements and its impacts on ecosystem processes such as nutrient cycling and productivity, especially in forest ecosystems, have not received the attention that this "master" variable deserves, On northern Vancouver Island, Canada, regenerating stands of western redcedar-western hemlock (CH) sites exhibit symptoms of nutrient deficiencies and slow growth, but this phenomenon does not occur on adjacent western hemlock- amabalis fir (HA) sites. We tested the hypothesis that differences in nutrient supply and distribution of plant species was caused by differences in moisture regime and redox potential. Redox potential, pH, soil aeration depth (steel rods), organic matter thickness, bulk density, soil carbon store, plant species distribution and richness were measured at five old-growth and five 10-year-old cutover blocks. Results of investigations confirmed that CH forests were wetter, had redox values lower than the critical 300mv and a shallower aerated zone, compared with adjacent regenerating HA sites. Fifty percent of the CH plots had redox values

  11. 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.

  12. In vivo NAD assay reveals the intracellular NAD contents and redox state in healthy human brain and their age dependences.

    PubMed

    Zhu, Xiao-Hong; Lu, Ming; Lee, Byeong-Yeul; Ugurbil, Kamil; Chen, Wei

    2015-03-03

    NAD is an essential metabolite that exists in NAD(+) or NADH form in all living cells. Despite its critical roles in regulating mitochondrial energy production through the NAD(+)/NADH redox state and modulating cellular signaling processes through the activity of the NAD(+)-dependent enzymes, the method for quantifying intracellular NAD contents and redox state is limited to a few in vitro or ex vivo assays, which are not suitable for studying a living brain or organ. Here, we present a magnetic resonance (MR) -based in vivo NAD assay that uses the high-field MR scanner and is capable of noninvasively assessing NAD(+) and NADH contents and the NAD(+)/NADH redox state in intact human brain. The results of this study provide the first insight, to our knowledge, into the cellular NAD concentrations and redox state in the brains of healthy volunteers. Furthermore, an age-dependent increase of intracellular NADH and age-dependent reductions in NAD(+), total NAD contents, and NAD(+)/NADH redox potential of the healthy human brain were revealed in this study. The overall findings not only provide direct evidence of declined mitochondrial functions and altered NAD homeostasis that accompany the normal aging process but also, elucidate the merits and potentials of this new NAD assay for noninvasively studying the intracellular NAD metabolism and redox state in normal and diseased human brain or other organs in situ.

  13. In vivo NAD assay reveals the intracellular NAD contents and redox state in healthy human brain and their age dependences

    PubMed Central

    Zhu, Xiao-Hong; Lu, Ming; Lee, Byeong-Yeul; Ugurbil, Kamil; Chen, Wei

    2015-01-01

    NAD is an essential metabolite that exists in NAD+ or NADH form in all living cells. Despite its critical roles in regulating mitochondrial energy production through the NAD+/NADH redox state and modulating cellular signaling processes through the activity of the NAD+-dependent enzymes, the method for quantifying intracellular NAD contents and redox state is limited to a few in vitro or ex vivo assays, which are not suitable for studying a living brain or organ. Here, we present a magnetic resonance (MR) -based in vivo NAD assay that uses the high-field MR scanner and is capable of noninvasively assessing NAD+ and NADH contents and the NAD+/NADH redox state in intact human brain. The results of this study provide the first insight, to our knowledge, into the cellular NAD concentrations and redox state in the brains of healthy volunteers. Furthermore, an age-dependent increase of intracellular NADH and age-dependent reductions in NAD+, total NAD contents, and NAD+/NADH redox potential of the healthy human brain were revealed in this study. The overall findings not only provide direct evidence of declined mitochondrial functions and altered NAD homeostasis that accompany the normal aging process but also, elucidate the merits and potentials of this new NAD assay for noninvasively studying the intracellular NAD metabolism and redox state in normal and diseased human brain or other organs in situ. PMID:25730862

  14. Redox potential - field measurements - meassured vs. expected values

    NASA Astrophysics Data System (ADS)

    Stavělová, Monika; Kovář, Martin

    2016-04-01

    Oxidation and reduction (redox) potential is an important and theoretically very well defined parameter and can be calculated accurately. Its value is determinative for management of many electrochemical processes, chemical redox technologies as well as biotechnologies. To measure the redox value that would correspond with the accuracy level of theoretical calculations in field or operational conditions is however nearly impossible. Redox is in practice measured using combined argentochloride electrode with subsequent value conversion to standard hydrogen electrode (EH). Argentochloride electrode does not allow for precise calibration. Prior to the measurement the accuracy of measurement of particular electrode can only be verified in comparative/control solution with value corresponding with oxic conditions (25°C: +220 mV argentochloride electrode, i.e.. +427 mV after conversion to EH). A commercial product of stabile comparative solution for anoxic conditions is not available and therefore not used in every day practice - accuracy of negative redox is not verified. In this presentation results of two tests will be presented: a) monitoring during dynamic groundwater sampling from eight monitoring wells at a site contaminated by chlorinated ethenes (i.e. post-oxic to anoxic conditions) and b) laboratory test of groundwater contaminated by arsenic from two sites during reaction with highly oxidized compounds of iron (ferrates) - i.e. strongly oxic conditions. In both tests a simultaneous measurement by four argentochloride electrodes was implemented - all four electrodes were prior to the test maintained expertly. The redox values of testing electrodes in a comparative solution varied by max. 6 mV. The redox values measured by four electrodes in both anoxic and oxic variant varied by tens to a hundred mV, while with growing time of test the variance of measured redox values increased in both oxic and anoxic variant. Therefore the interpretation of measured redox

  15. Confocal imaging of glutathione redox potential in living plant cells.

    PubMed

    Schwarzländer, M; Fricker, M D; Müller, C; Marty, L; Brach, T; Novak, J; Sweetlove, L J; Hell, R; Meyer, A J

    2008-08-01

    Reduction-oxidation-sensitive green fluorescent protein (roGFP1 and roGFP2) were expressed in different sub-cellular compartments of Arabidopsis and tobacco leaves to empirically determine their performance as ratiometric redox sensors for confocal imaging in planta. A lower redox-dependent change in fluorescence in combination with reduced excitation efficiency at 488 nm resulted in a significantly lower dynamic range of roGFP1 than for roGFP2. Nevertheless, when targeted to the cytosol and mitochondria of Arabidopsis leaves both roGFPs consistently indicated redox potentials of about -320 mV in the cytosol and -360 mV in the mitochondria after pH correction for the more alkaline matrix pH. Ratio measurements were consistent throughout the epidermal cell layer, but results might be attenuated deeper within the leaf tissue. Specific interaction of both roGFPs with glutaredoxin in vitro strongly suggests that in situ both variants preferentially act as sensors for the glutathione redox potential. roGFP2 targeted to plastids and peroxisomes in epidermal cells of tobacco leaves was slightly less reduced than in other plasmatic compartments, but still indicated a highly reduced glutathione pool. The only oxidizing compartment was the lumen of the endoplasmic reticulum, in which roGFP2 was almost completely oxidized. In all compartments tested, roGFP2 reversibly responded to perfusion with H(2)O(2) and DTT, further emphasizing that roGFP2 is a reliable probe for dynamic redox imaging in planta. Reliability of roGFP1 measurements might be obscured though in extended time courses as it was observed that intense irradiation of roGFP1 at 405 nm can lead to progressive photoisomerization and thus a redox-independent change of fluorescence excitation ratios.

  16. Sulfonamido tripods: tuning redox potentials via ligand modifications

    PubMed Central

    Lau, Nathanael; Ziller, Joseph W.

    2014-01-01

    A series of FeII–OH2 complexes were synthesized with ligands based on the tetradentate sulfonamido tripod N,N',N"-[2,2',2"-nitrilotris(ethane-2,1-diyl)]-tris-({R-Ph}-sulfonamido). These complexes differ by the substituent on the aryl rings and were fully characterized, including their molecular structures via X-ray diffraction methods. All the complexes were five-coordinate with trigonal bipyramidal geometry. A linear correlation was observed between the electronic effects of each ligand, given by the Hammett constants of the para-substituents, and the potential of the FeII/FeIII redox couple, which were determined using cyclic voltammetry. It was found that the range of redox potentials for the complexes spanned approximately 160 mV. PMID:25419035

  17. Online monitoring of Mezcal fermentation based on redox potential measurements.

    PubMed

    Escalante-Minakata, P; Ibarra-Junquera, V; Rosu, H C; De León-Rodríguez, A; González-García, R

    2009-01-01

    We describe an algorithm for the continuous monitoring of the biomass and ethanol concentrations as well as the growth rate in the Mezcal fermentation process. The algorithm performs its task having available only the online measurements of the redox potential. The procedure combines an artificial neural network (ANN) that relates the redox potential to the ethanol and biomass concentrations with a nonlinear observer-based algorithm that uses the ANN biomass estimations to infer the growth rate of this fermentation process. The results show that the redox potential is a valuable indicator of the metabolic activity of the microorganisms during Mezcal fermentation. In addition, the estimated growth rate can be considered as a direct evidence of the presence of mixed culture growth in the process. Usually, mixtures of microorganisms could be intuitively clear in this kind of processes; however, the total biomass data do not provide definite evidence by themselves. In this paper, the detailed design of the software sensor as well as its experimental application is presented at the laboratory level.

  18. Redox electrodeposition polymers: adaptation of the redox potential of polymer-bound Os complexes for bioanalytical applications.

    PubMed

    Guschin, Dmitrii A; Castillo, John; Dimcheva, Nina; Schuhmann, Wolfgang

    2010-10-01

    The design of polymers carrying suitable ligands for coordinating Os complexes in ligand exchange reactions against labile chloro ligands is a strategy for the synthesis of redox polymers with bound Os centers which exhibit a wide variation in their redox potential. This strategy is applied to polymers with an additional variation of the properties of the polymer backbone with respect to pH-dependent solubility, monomer composition, hydrophilicity etc. A library of Os-complex-modified electrodeposition polymers was synthesized and initially tested with respect to their electron-transfer ability in combination with enzymes such as glucose oxidase, cellobiose dehydrogenase, and PQQ-dependent glucose dehydrogenase entrapped during the pH-induced deposition process. The different polymer-bound Os complexes in a library containing 50 different redox polymers allowed the statistical evaluation of the impact of an individual ligand to the overall redox potential of an Os complex. Using a simple linear regression algorithm prediction of the redox potential of Os complexes becomes feasible. Thus, a redox polymer can now be designed to optimally interact in electron-transfer reactions with a selected enzyme.

  19. 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.

  20. Redox Potentials, Laccase Oxidation, and Antilarval Activities of Substituted Phenols

    PubMed Central

    Prasain, Keshar; Nguyen, Thi D. T.; Gorman, Maureen J.; Barrigan, Lydia M.; Peng, Zeyu; Kanost, Michael R.; Syed, Lateef U.; Li, Jun; Zhu, Kun Yan; Hua, Duy H.

    2012-01-01

    Laccases are copper-containing oxidases that are involved in sclerotization of the cuticle of mosquitoes and other insects. Oxidation of exogenous compounds by insect laccases may have the potential to produce reactive species toxic to insects. We investigated two classes of substituted phenolic compounds, halogenated di- and trihydroxybenzenes and substituted di-tert-butylphenols, on redox potential, oxidation by laccase and effects on mosquito larval growth. An inverse correlation between the oxidation potentials and laccase activity of halogenated hydroxybenzenes was found. Substituted di-tert-butylphenols however were found to impact mosquito larval growth and survival. In particular, 2,4-di-tert-butyl-6-(3-methyl-2-butenyl)phenol (15) caused greater than 98% mortality of Anopheles gambiae larvae in a concentration of 180 nM, whereas 2-(3,5-di-tert-butyl-4-hydroxyphenyl)-2-methylpropanal oxime (13) and 6,8-di-tert-butyl-2,2-dimethyl-3,4-dihydro-2H-chromene (33) caused 93% and 92% mortalities in concentrations of 3.4 and 3.7 μM, respectively. Larvae treated with di-tert-butylphenolic compounds died just before pupation. PMID:22300888

  1. Geothrix fermentans Secretes Two Different Redox-Active Compounds To Utilize Electron Acceptors across a Wide Range of Redox Potentials

    PubMed Central

    Mehta-Kolte, Misha G.

    2012-01-01

    The current understanding of dissimilatory metal reduction is based primarily on isolates from the proteobacterial genera Geobacter and Shewanella. However, environments undergoing active Fe(III) reduction often harbor less-well-studied phyla that are equally abundant. In this work, electrochemical techniques were used to analyze respiratory electron transfer by the only known Fe(III)-reducing representative of the Acidobacteria, Geothrix fermentans. In contrast to previously characterized metal-reducing bacteria, which typically reach maximal rates of respiration at electron acceptor potentials of 0 V versus standard hydrogen electrode (SHE), G. fermentans required potentials as high as 0.55 V to respire at its maximum rate. In addition, G. fermentans secreted two different soluble redox-active electron shuttles with separate redox potentials (−0.2 V and 0.3 V). The compound with the lower midpoint potential, responsible for 20 to 30% of electron transfer activity, was riboflavin. The behavior of the higher-potential compound was consistent with hydrophilic UV-fluorescent molecules previously found in G. fermentans supernatants. Both electron shuttles were also produced when cultures were grown with Fe(III), but not when fumarate was the electron acceptor. This study reveals that Geothrix is able to take advantage of higher-redox-potential environments, demonstrates that secretion of flavin-based shuttles is not confined to Shewanella, and points to the existence of high-potential-redox-active compounds involved in extracellular electron transfer. Based on differences between the respiratory strategies of Geothrix and Geobacter, these two groups of bacteria could exist in distinctive environmental niches defined by redox potential. PMID:22843516

  2. 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.

  3. A fluorescence-based assay for measuring the redox potential of 5-lipoxygenase inhibitors.

    PubMed

    Lee, Sangchul; Park, Youngsam; Kim, Junghwan; Han, Sung-Jun

    2014-01-01

    The activities and side effects of 5-lipoxygenase (5-LO) inhibitors can be predicted by identifying their redox mechanisms. In this study, we developed a fluorescence-based method to measure the redox potential of 5-LO inhibitors and compared it to the conventional, absorbance-based method. After the pseudo-peroxidase reaction, the amount of remaining lipid peroxide was quantified using the H2DCFDA (2',7'-dichlorodihydrofluorescein diacetate) fluorescence dye. Our method showed large signal windows and provided comparable redox potential values. Importantly, the redox mechanisms of known inhibitors were accurately measured with the fluorescence assay, whereas the conventional, absorbance-based method showed contradictory results. Our findings suggest that our developed method is a better alternative for classifying the redox potential of 5-LO inhibitors, and the fluorescence assay can be effectively used to study the mechanisms of action that are related to redox cycling.

  4. Perspectives on Proterozoic surface ocean redox from iodine contents in ancient and recent carbonate

    NASA Astrophysics Data System (ADS)

    Hardisty, Dalton S.; Lu, Zunli; Bekker, Andrey; Diamond, Charles W.; Gill, Benjamin C.; Jiang, Ganqing; Kah, Linda C.; Knoll, Andrew H.; Loyd, Sean J.; Osburn, Magdalena R.; Planavsky, Noah J.; Wang, Chunjiang; Zhou, Xiaoli; Lyons, Timothy W.

    2017-04-01

    The Proterozoic Eon hosted the emergence and initial recorded diversification of eukaryotes. Oxygen levels in the shallow marine settings critical to these events were lower than today's, although how much lower is debated. Here, we use concentrations of iodate (the oxidized iodine species) in shallow-marine limestones and dolostones to generate the first comprehensive record of Proterozoic near-surface marine redox conditions. The iodine proxy is sensitive to both local oxygen availability and the relative proximity to anoxic waters. To assess the validity of our approach, Neogene-Quaternary carbonates are used to demonstrate that diagenesis most often decreases and is unlikely to increase carbonate-iodine contents. Despite the potential for diagenetic loss, maximum Proterozoic carbonate iodine levels are elevated relative to those of the Archean, particularly during the Lomagundi and Shuram carbon isotope excursions of the Paleo- and Neoproterozoic, respectively. For the Shuram anomaly, comparisons to Neogene-Quaternary carbonates suggest that diagenesis is not responsible for the observed iodine trends. The baseline low iodine levels in Proterozoic carbonates, relative to the Phanerozoic, are linked to a shallow oxic-anoxic interface. Oxygen concentrations in surface waters would have at least intermittently been above the threshold required to support eukaryotes. However, the diagnostically low iodine data from mid-Proterozoic shallow-water carbonates, relative to those of the bracketing time intervals, are consistent with a dynamic chemocline and anoxic waters that would have episodically mixed upward and laterally into the shallow oceans. This redox instability may have challenged early eukaryotic diversification and expansion, creating an evolutionary landscape unfavorable for the emergence of animals.

  5. Electrical/optical dual-function redox potential transistor

    PubMed Central

    Li, Shunpu; Wang, Wensi; Xu, Ju; Chu, Daping; Shen, Z. John; Roy, Saibal

    2013-01-01

    We demonstrate a new type of transistors, the electrical/optical “dual-function redox-potential transistors”, which is solution processable and environmentally stable. This device consists of vertically staked electrodes that act as gate, emitter and collector. It can perform as a normal transistor, whilst one electrode which is sensitised by dye enables to generate photocurrent when illuminated. Solution processable oxide-nanoparticles were used to form various functional layers, which allow an electrolyte to penetrate through and, consequently, the current between emitter and collector can be controlled by the gate potential modulated distribution of ions. The result here shows that the device performs with high ON-current under low driving voltage (<1 V), while the transistor performance can readily be controlled by photo-illumination. Such device with combined optical and electrical functionalities allows single device to perform the tasks that are usually done by a circuit/system with multiple optical and electrical components, and it is promising for various applications. PMID:24310311

  6. Redox potentials of uranium in molten eutectic mixture of lithium, potassium, and cesium chlorides

    NASA Astrophysics Data System (ADS)

    Maltsev, D. S.; Volkovich, V. A.; Vasin, B. D.

    2016-08-01

    The behavior of uranium(III) and (IV) ions in the melts based on the eutectic mixture of lithium, potassium, and cesium chlorides has been studied using cyclic voltammetry in the range of 573-1073 K. The red-ox potentials of uranium have been determined and formal standard E U(III)/U(IV)* red-ox potentials have been calculated.

  7. A catalytic approach to estimate the redox potential of heme-peroxidases

    SciTech Connect

    Ayala, Marcela . E-mail: maa@ibt.unam.mx; Roman, Rosa; Vazquez-Duhalt, Rafael

    2007-06-08

    The redox potential of heme-peroxidases varies according to a combination of structural components within the active site and its vicinities. For each peroxidase, this redox potential imposes a thermodynamic threshold to the range of oxidizable substrates. However, the instability of enzymatic intermediates during the catalytic cycle precludes the use of direct voltammetry to measure the redox potential of most peroxidases. Here we describe a novel approach to estimate the redox potential of peroxidases, which directly depends on the catalytic performance of the activated enzyme. Selected p-substituted phenols are used as substrates for the estimations. The results obtained with this catalytic approach correlate well with the oxidative capacity predicted by the redox potential of the Fe(III)/Fe(II) couple.

  8. Miniaturized redox potential probe for in situ environmental monitoring.

    PubMed

    Jang, Am; Lee, Jin-Hwan; Bhadri, Prashant R; Kumar, Suresh A; Timmons, William; Beyette, Fred R; Papautsky, Ian; Bishop, Paul L

    2005-08-15

    The need for accurate, robust in situ microscale monitoring of oxidation-reduction potentials (ORP) is required for continuous soil pore water quality monitoring. We are developing a suite of self-contained microelectrodes that can be used in the environment, such as at Superfund sites, to monitor ORP in contaminated soils and sediments. This paper presents details on our development of microelectrode sensor arrays for ORP measurements. The electrochemical performance of these ORP electrodes was fully characterized by measuring redox potentials in standard solutions. It found that the newly developed integrated ORP microelectrodes produced a very stable voltage response (the corresponding rate of the integrated microelectrode potential change was in the range of 0.6-1.1 mV/min), even when the measurement was carried out outside of a Faraday cage where signals from most conventional microelectrodes are usually inhibited by external electrical nose. These new microelectrodes were easier to fabricate and were more robust than conventional microelectrodes. The tip size of the integrated ORP microelectrode was approximately 200 nm square, with a taper angle of approximately 20 degrees and a length of 57 microm. The integrated ORP microelectrode exhibited better signal stability and substantially shorter response times (from less than a few milliseconds to 30 s, depending on the standard solution used) than the commercial millielectrode (a few minutes). Compared with the slope of the commercial millelectrode, the slope of the integrated microelectrode (61.5 mV/pH) was closerto the ideal slope against quinhydrone calibration solutions. Therefore, it is to be expected that the newly developed ORP microelectrode may have wider applications in contaminated soils, biofilms, and sediments.

  9. Astatine standard redox potentials and speciation in acidic medium.

    PubMed

    Champion, J; Alliot, C; Renault, E; Mokili, B M; Chérel, M; Galland, N; Montavon, G

    2010-01-14

    A combined experimental and theoretical approach is used to define astatine (At) speciation in acidic aqueous solution and to answer the two main questions raised from literature data: does At(0) exist in aqueous solution and what is the chemical form of At(+III), if it exists. The experimental approach considers that a given species is characterized by its distribution coefficient (D) experimentally determined in a biphasic system. The change in speciation arising from a change in experimental conditions is observed by a change in D value. The theoretical approach involves quasi-relativistic quantum chemistry calculations. The results show that At at the oxidation state 0 cannot exist in aqueous solution. The three oxidation states present in the range of water stability are At(-I), At(+I), and At(+III) and exist as At(-), At(+), and AtO(+), respectively, in the 1-2 pH range. The standard redox potentials of the At(+)/At(-) and AtO(+)/At(+) couples have been determined, the respective values being 0.36 +/- 0.01 and 0.74 +/- 0.01 V vs NHE.

  10. 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

  11. Characterization of plasma thiol redox potential in a common marmoset model of aging.

    PubMed

    Roede, James R; Uppal, Karan; Liang, Yongliang; Promislow, Daniel E L; Wachtman, Lynn M; Jones, Dean P

    2013-01-01

    Due to its short lifespan, ease of use and age-related pathologies that mirror those observed in humans, the common marmoset (Callithrix jacchus) is poised to become a standard nonhuman primate model of aging. Blood and extracellular fluid possess two major thiol-dependent redox nodes involving cysteine (Cys), cystine (CySS), glutathione (GSH) and glutathione disulfide (GSSG). Alteration in these plasma redox nodes significantly affects cellular physiology, and oxidation of the plasma Cys/CySS redox potential (E hCySS) is associated with aging and disease risk in humans. The purpose of this study was to determine age-related changes in plasma redox metabolites and corresponding redox potentials (E h) to further validate the marmoset as a nonhuman primate model of aging. We measured plasma thiol redox states in marmosets and used existing human data with multivariate adaptive regression splines (MARS) to model the relationships between age and redox metabolites. A classification accuracy of 70.2% and an AUC of 0.703 were achieved using the MARS model built from the marmoset redox data to classify the human samples as young or old. These results show that common marmosets provide a useful model for thiol redox biology of aging.

  12. Development of redox potential-controlled schemes for very-high-gravity ethanol fermentation.

    PubMed

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

    2011-04-20

    Fermentation redox potential reflects the momentary physiological status of organisms. Controlling redox potential can modulate the redistribution of intracellular metabolic flux to favor the formation of the desired metabolite. Accordingly, we have developed three redox potential-controlled schemes to maximize their effects on the very-high-gravity (VHG) ethanol fermentation. They are aeration-controlled scheme (ACS), glucose-controlled feeding scheme (GCFS), and combined chemostat and aeration-controlled scheme (CCACS). These schemes can maintain fermentation redox potential at a prescribed level (i.e., -50, -100, and -150 mV) by supplementing sterile air, fresh glucose media, or a combination of sterile air and fresh glucose media into a fermenter to counteract the decline of redox potential due to yeast growth. When ACS was employed, the fermentation efficiency at -150 mV is superior to the other two redox potential levels especially when the initial glucose concentration is higher than 250 g/l. The redox potential-controlled period for ACS, GCFS, and CCACS at -150 mV under the same 200 g glucose/l condition was 2.5, 21.7 and 64.6h and the corresponding fermentation efficiency was 85.9,89.3 and 92.7%, respectively.

  13. Redox reactions with empirical potentials: atomistic battery discharge simulations.

    PubMed

    Dapp, Wolf B; Müser, Martin H

    2013-08-14

    Batteries are pivotal components in overcoming some of today's greatest technological challenges. Yet to date there is no self-consistent atomistic description of a complete battery. We take first steps toward modeling of a battery as a whole microscopically. Our focus lies on phenomena occurring at the electrode-electrolyte interface which are not easily studied with other methods. We use the redox split-charge equilibration (redoxSQE) method that assigns a discrete ionization state to each atom. Along with exchanging partial charges across bonds, atoms can swap integer charges. With redoxSQE we study the discharge behavior of a nano-battery, and demonstrate that this reproduces the generic properties of a macroscopic battery qualitatively. Examples are the dependence of the battery's capacity on temperature and discharge rate, as well as performance degradation upon recharge.

  14. Wiring of pyranose dehydrogenase with osmium polymers of different redox potentials.

    PubMed

    Zafar, Muhammad Nadeem; Tasca, Federico; Boland, Susan; Kujawa, Magdalena; Patel, Ilabahen; Peterbauer, Clemens K; Leech, Dónal; Gorton, Lo

    2010-11-01

    In this study, five different flexible osmium based redox polymers were investigated for their ability to efficiently "wire" the oxidoreductase pyranose dehydrogenase (PDH, EC 1.1.99.29) from Agaricus meleagris, on graphite electrodes for possible applications in biofuel cells. A series of newly synthesised osmium based redox polymers covering the potential range between -270 and +160 mV vs. Ag|AgCl (0.1M KCl) was used. The performance of the redox polymers for enzyme wiring was investigated using glucose as substrate. The optimal operational conditions such as pH and potential were investigated.

  15. 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.

  16. pH, redox potential and local biofilm potential microenvironments within Geobacter sulfurreducens biofilms and their roles in electron transfer.

    PubMed

    Babauta, Jerome T; Nguyen, Hung Duc; Harrington, Timothy D; Renslow, Ryan; Beyenal, Haluk

    2012-10-01

    The limitation of pH inside electrode-respiring biofilms is a well-known concept. However, little is known about how pH and redox potential are affected by increasing current inside biofilms respiring on electrodes. Quantifying the variations in pH and redox potential with increasing current is needed to determine how electron transfer is tied to proton transfer within the biofilm. In this research, we quantified pH and redox potential variations in electrode-respiring Geobacter sulfurreducens biofilms as a function of respiration rates, measured as current. We also characterized pH and redox potential at the counter electrode. We concluded that (1) pH continued to decrease in the biofilm through different growth phases, showing that the pH is not always a limiting factor in a biofilm and (2) decreasing pH and increasing redox potential at the biofilm electrode were associated only with the biofilm, demonstrating that G. sulfurreducens biofilms respire in a unique internal environment. Redox potential inside the biofilm was also compared to the local biofilm potential measured by a graphite microelectrode, where the tip of the microelectrode was allowed to acclimatize inside the biofilm.

  17. pH, Redox Potential and Local Biofilm Potential Microenvironments Within Geobacter sulfurreducens Biofilms and Their Roles in Electron Transfer

    PubMed Central

    Babauta, Jerome T.; Nguyen, Hung Duc; Harrington, Timothy D.; Renslow, Ryan; Beyenal, Haluk

    2012-01-01

    The limitation of pH inside electrode-respiring biofilms is a well-known concept. However, little is known about how pH and redox potential are affected by increasing current inside biofilms respiring on electrodes. Quantifying the variations in pH and redox potential with increasing current is needed to determine how electron transfer is tied to proton transfer within the biofilm. In this research, we quantified pH and redox potential variations in electrode-respiring Geobacter sulfurreducens biofilms as a function of respiration rates, measured as current. We also characterized pH and redox potential at the counter electrode. We concluded that (1) pH continued to decrease in the biofilm through different growth phases, showing that the pH is not always a limiting factor in a biofilm and (2) decreasing pH and increasing redox potential at the biofilm electrode were associated only with the biofilm, demonstrating that G. sulfurreducens biofilms respire in a unique internal environment. Redox potential inside the biofilm was also compared to the local biofilm potential measured by a graphite microelectrode, where the tip of the micro-electrode was allowed to acclimatize inside the biofilm. PMID:22549331

  18. A high redox potential form of cytochrome c550 in photosystem II from Thermosynechococcus elongatus.

    PubMed

    Guerrero, Fernando; Sedoud, Arezki; Kirilovsky, Diana; Rutherford, A William; Ortega, José M; Roncel, Mercedes

    2011-02-25

    Cytochrome c(550) (cyt c(550)) is a component of photosystem II (PSII) from cyanobacteria, red algae, and some other eukaryotic algae. Its physiological role remains unclear. In the present work, measurements of the midpoint redox potential (E(m)) were performed using intact PSII core complexes preparations from a histidine-tagged PSII mutant strain of the thermophilic cyanobacterium Thermosynechococcus (T.) elongatus. When redox titrations were done in the absence of redox mediators, an E(m) value of +200 mV was obtained for cyt c(550). This value is ∼300 mV more positive than that previously measured in the presence of mediators (E(m) = -80 mV). The shift from the high potential form (E(m) = +200 mV) to the low potential form (E(m) = -80 mV) of cyt c(550) is attributed to conformational changes, triggered by the reduction of a component of PSII that is sequestered and out of equilibrium with the medium, most likely the Mn(4)Ca cluster. This reduction can occur when reduced low potential redox mediators are present or under highly reducing conditions even in the absence of mediators. Based on these observations, it is suggested that the E(m) of +200 mV obtained without mediators could be the physiological redox potential of the cyt c(550) in PSII. This value opens the possibility of a redox function for cyt c(550) in PSII.

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

    PubMed Central

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

    2016-01-01

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

  20. A High Redox Potential Laccase from Pycnoporus sanguineus RP15: Potential Application for Dye Decolorization

    PubMed Central

    Zimbardi, Ana L. R. L.; Camargo, Priscila F.; Carli, Sibeli; Aquino Neto, Sidney; Meleiro, Luana P.; Rosa, Jose C.; De Andrade, Adalgisa R.; Jorge, João A.; Furriel, Rosa P. M.

    2016-01-01

    Laccase production by Pycnoporus sanguineus RP15 grown in wheat bran and corncob under solid-state fermentation was optimized by response surface methodology using a Central Composite Rotational Design. A laccase (Lacps1) was purified and characterized and the potential of the pure Lacps1 and the crude culture extract for synthetic dye decolorization was evaluated. At optimal conditions (eight days, 26 °C, 18% (w/w) milled corncob, 0.8% (w/w) NH4Cl and 50 mmol·L−1 CuSO4, initial moisture 4.1 mL·g−1), the laccase activity reached 138.6 ± 13.2 U·g−1. Lacps1 was a monomeric glycoprotein (67 kDa, 24% carbohydrate). Optimum pH and temperature for the oxidation of 2,2’-azino-bis(3-ethylbenzthiazoline-6-sulfonate) (ABTS) were 4.4 and 74.4 °C, respectively. Lacps1 was stable at pH 3.0–8.0, and after two hours at 55–60 °C, presenting high redox potential (0.747 V vs. NHE). ABTS was oxidized with an apparent affinity constant of 147.0 ± 6.4 μmol·L−1, maximum velocity of 413.4 ± 21.2 U·mg−1 and catalytic efficiency of 3140.1 ± 149.6 L·mmol−1·s−1. The maximum decolorization percentages of bromophenol blue (BPB), remazol brilliant blue R and reactive blue 4 (RB4), at 25 or 40 °C without redox mediators, reached 90%, 80% and 60%, respectively, using either pure Lacps1 or the crude extract. This is the first study of the decolorization of BPB and RB4 by a P. sanguineus laccase. The data suggested good potential for treatment of industrial dye-containing effluents. PMID:27164083

  1. A High Redox Potential Laccase from Pycnoporus sanguineus RP15: Potential Application for Dye Decolorization.

    PubMed

    Zimbardi, Ana L R L; Camargo, Priscila F; Carli, Sibeli; Aquino Neto, Sidney; Meleiro, Luana P; Rosa, Jose C; De Andrade, Adalgisa R; Jorge, João A; Furriel, Rosa P M

    2016-05-05

    Laccase production by Pycnoporus sanguineus RP15 grown in wheat bran and corncob under solid-state fermentation was optimized by response surface methodology using a Central Composite Rotational Design. A laccase (Lacps1) was purified and characterized and the potential of the pure Lacps1 and the crude culture extract for synthetic dye decolorization was evaluated. At optimal conditions (eight days, 26 °C, 18% (w/w) milled corncob, 0.8% (w/w) NH₄Cl and 50 mmol·L(-1) CuSO₄, initial moisture 4.1 mL·g(-1)), the laccase activity reached 138.6 ± 13.2 U·g(-1). Lacps1 was a monomeric glycoprotein (67 kDa, 24% carbohydrate). Optimum pH and temperature for the oxidation of 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonate) (ABTS) were 4.4 and 74.4 °C, respectively. Lacps1 was stable at pH 3.0-8.0, and after two hours at 55-60 °C, presenting high redox potential (0.747 V vs. NHE). ABTS was oxidized with an apparent affinity constant of 147.0 ± 6.4 μmol·L(-1), maximum velocity of 413.4 ± 21.2 U·mg(-1) and catalytic efficiency of 3140.1 ± 149.6 L·mmol(-1)·s(-1). The maximum decolorization percentages of bromophenol blue (BPB), remazol brilliant blue R and reactive blue 4 (RB4), at 25 or 40 °C without redox mediators, reached 90%, 80% and 60%, respectively, using either pure Lacps1 or the crude extract. This is the first study of the decolorization of BPB and RB4 by a P. sanguineus laccase. The data suggested good potential for treatment of industrial dye-containing effluents.

  2. The concept of electron activity and its relation to redox potentials in aqueous geochemical systems

    USGS Publications Warehouse

    Thorstenson, D.C.

    1984-01-01

    The definition of a formal thermodynamic activity of electrons in redox reactions appears in the literature of the 1920's. The concept of pe as -log (electron activity) was introduced by Jorgensen in 1945 and popularized in the geochemical literature by Sillen, who considered pe and pH as master variables in geochemical reactions. The physical significance of the concept of electron activity was challenged as early as 1928. However, only in the last two decades have sufficient thermodynamic data become available to examine this question quantitatively. The chemical nature of hydrated electrons differs greatly from that of hydrated protons, and thermodynamic data show that hydrated electrons cannot exist at physically meaningful equilibrium concentrations under natural conditions. This has important consequences for the understanding of redox processes in natural waters. These are: (1) the analogy between pe and pH as master variables is generally carried much further than is justified; (2) a thermodynamically meaningful value of redox potential cannot be assigned to disequilibrium systems; (3) the most useful approach to the study of redox characteristics is the analysis and study of multiple redox couples in the system; and (4) for all practical purposes, thermodynamically defined redox potentials do not exist (and thus cannot be measured) in natural waters. The overall implication for natural systems is that, in terms of redox reactions, each case must be considered on an individual and detailed basis. Field studies would appear to be a mandatory part of any site-specific study; conclusions regarding redox processes cannot be based solely on electrode measurements or thermodynamic stability calculations. (USGS)

  3. Effects of ph, carbonate, orthophosphate, and redox potential on cuprosolvency

    SciTech Connect

    Schock, M.R.; Lytle, D.A.; Clement, J.A.

    1995-12-01

    A comprehensive solubility model for copper in drinking water has been developed, that is consistent with available data for copper dissolution and passivation in drinking water systems. Copper solubility (cuprosolvency) is greatly affected by the redox conditions of the systems. The concentration of Cu(I) is dominated by Cu{sub 2}O(s) or CuOH(s) solid phases, plus soluble aqueous ammonia and chloride complexes. In new piping, the concentration of Cu(II) is mainly governed by Cu(OH){sub 2}(s) (cupric hydroxide), rather than CuO(s) (tenorite) or Cu{sub 2}(OH){sub 2}CO{sub 3}(s)(malachite). Complexation of Cu(II) by DIC and hydroxide ion is extremely important. Increases in DIC are predicted to cause significant increases in copper solubility in the pH range of 7.5--10. Utilities may trade off increasing cuprosolvency by DIC addition for ensuring adequate buffering intensity in the finished water. Sufficient dosages of orthophosphate in the pH range of 6.5 to 7.5 may reduce cuprosolvency under oxidizing conditions. Sulfate may decrease cuprosolvency under some conditions, or may interfere with the formation of cupric hydroxide films under mildly alkaline conditions. Dissolved oxygen and chlorine residual play complicated roles in determining copper concentrations after various standing times. Frequently, 48--72 hours are necessary to reach equilibrium levels of copper in disinfected systems.

  4. Quantitative measurement of redox potential in hypoxic cells using SERS nanosensors

    NASA Astrophysics Data System (ADS)

    Jiang, Jing; Auchinvole, Craig; Fisher, Kate; Campbell, Colin J.

    2014-09-01

    Hypoxia is considered to be a reductive disorder of cells that is caused either by a lack of oxygen or by the dysregulation of metabolic pathways and is thought to play a role in the pathology of diseases including stroke and cancer. One aspect of hypoxia that remains poorly investigated is the dysregulation of cellular redox potential and its role in controlling biological pathway activation. Since there is currently no way of quantitatively measuring the intracellular redox potential of hypoxic cells, this provided us with the motivation to develop optical nanosensors whose Surface-Enhanced Raman (SER) spectrum provides a quantitative measure of redox potential in hypoxic cells. Our nanosensors are made from organic reporter molecules that show oxidation-state-dependent changes in the Raman spectrum and are chemically adsorbed onto gold nanoshells. These nanosensors can be taken up by cells, and by collecting the SER spectrum we can calculate the localised intracellular redox potential from single hypoxic cells in a non-invasive, reversible way.Hypoxia is considered to be a reductive disorder of cells that is caused either by a lack of oxygen or by the dysregulation of metabolic pathways and is thought to play a role in the pathology of diseases including stroke and cancer. One aspect of hypoxia that remains poorly investigated is the dysregulation of cellular redox potential and its role in controlling biological pathway activation. Since there is currently no way of quantitatively measuring the intracellular redox potential of hypoxic cells, this provided us with the motivation to develop optical nanosensors whose Surface-Enhanced Raman (SER) spectrum provides a quantitative measure of redox potential in hypoxic cells. Our nanosensors are made from organic reporter molecules that show oxidation-state-dependent changes in the Raman spectrum and are chemically adsorbed onto gold nanoshells. These nanosensors can be taken up by cells, and by collecting the SER

  5. Potential role of glutathione in evolution of thiol-based redox signaling sites in proteins

    PubMed Central

    Mohanasundaram, Kaavya A.; Haworth, Naomi L.; Grover, Mani P.; Crowley, Tamsyn M.; Goscinski, Andrzej; Wouters, Merridee A.

    2015-01-01

    Cysteine is susceptible to a variety of modifications by reactive oxygen and nitrogen oxide species, including glutathionylation; and when two cysteines are involved, disulfide formation. Glutathione-cysteine adducts may be removed from proteins by glutaredoxin, whereas disulfides may be reduced by thioredoxin. Glutaredoxin is homologous to the disulfide-reducing thioredoxin and shares similar binding modes of the protein substrate. The evolution of these systems is not well characterized. When a single Cys is present in a protein, conjugation of the redox buffer glutathione may induce conformational changes, resulting in a simple redox switch that effects a signaling cascade. If a second cysteine is introduced into the sequence, the potential for disulfide formation exists. In favorable protein contexts, a bistable redox switch may be formed. Because of glutaredoxin's similarities to thioredoxin, the mutated protein may be immediately exapted into the thioredoxin-dependent redox cycle upon addition of the second cysteine. Here we searched for examples of protein substrates where the number of redox-active cysteine residues has changed throughout evolution. We focused on cross-strand disulfides (CSDs), the most common type of forbidden disulfide. We searched for proteins where the CSD is present, absent and also found as a single cysteine in protein orthologs. Three different proteins were selected for detailed study—CD4, ERO1, and AKT. We created phylogenetic trees, examining when the CSD residues were mutated during protein evolution. We posit that the primordial cysteine is likely to be the cysteine of the CSD which undergoes nucleophilic attack by thioredoxin. Thus, a redox-active disulfide may be introduced into a protein structure by stepwise mutation of two residues in the native sequence to Cys. By extension, evolutionary acquisition of structural disulfides in proteins can potentially occur via transition through a redox-active disulfide state. PMID

  6. Development of roGFP2-derived redox probes for measurement of the glutathione redox potential in the cytosol of severely glutathione-deficient rml1 seedlings

    PubMed Central

    Aller, Isabel; Rouhier, Nicolas; Meyer, Andreas J.

    2013-01-01

    Glutathione is important for detoxification, as a cofactor in biochemical reactions and as a thiol-redox buffer. The cytosolic glutathione buffer is normally highly reduced with glutathione redox potentials (EGSH) of more negative than −310 mV. Maintenance of such negative redox potential is achieved through continuous reduction of glutathione disulfide by glutathione reductase (GR). Deviations from steady state glutathione redox homeostasis have been discussed as a possible mean to alter the activity of redox-sensitive proteins through switching of critical thiol residues. To better understand such signaling mechanisms it is essential to be able to measure EGSH over a wide range from highly negative redox potentials down to potentials found in mutants that show already severe phenotypes. With the advent of redox-sensitive GFPs (roGFPs), understanding the in vivo dynamics of the thiol-based redox buffer system became within reach. The original roGFP versions, roGFP1 and roGFP2, however, have midpoint potentials between −280 and −290 mV rendering them fully oxidized in the ER and almost fully reduced in the cytosol, plastids, mitochondria, and peroxisomes. To extend the range of suitable probes we have engineered a roGFP2 derivative, roGFP2-iL, with a midpoint potential of about −238 mV. This value is within the range of redox potentials reported for homologous roGFP1-iX probes, albeit with different excitation properties. To allow rapid and specific equilibration with the glutathione pool, fusion constructs with human glutaredoxin 1 (GRX1) were generated and characterized in vitro. GRX1-roGFP2-iL proved to be suitable for in vivo redox potential measurements and extends the range of EGSH values that can be measured in vivo with roGFP2-based probes from about −320 mV for GRX1-roGFP2 down to about −210 mV for GRX1-roGFP2-iL. Using both probes in the cytosol of severely glutathione-deficient rml1 seedlings revealed an EGSH of about −260 mV in this mutant

  7. 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.

  8. Species-Specific Standard Redox Potential of Thiol-Disulfide Systems: A Key Parameter to Develop Agents against Oxidative Stress

    PubMed Central

    Mirzahosseini, Arash; Noszál, Béla

    2016-01-01

    Microscopic standard redox potential, a new physico-chemical parameter was introduced and determined to quantify thiol-disulfide equilibria of biological significance. The highly composite, codependent acid-base and redox equilibria of thiols could so far be converted into pH-dependent, apparent redox potentials (E’°) only. Since the formation of stable metal-thiolate complexes precludes the direct thiol-disulfide redox potential measurements by usual electrochemical techniques, an indirect method had to be elaborated. In this work, the species-specific, pH-independent standard redox potentials of glutathione were determined primarily by comparing it to 1-methylnicotinamide, the simplest NAD+ analogue. Secondarily, the species-specific standard redox potentials of the two-electron redox transitions of cysteamine, cysteine, homocysteine, penicillamine, and ovothiol were determined using their microscopic redox equilibrium constants with glutathione. The 30 different, microscopic standard redox potential values show close correlation with the respective thiolate basicities and provide sound means for the development of potent agents against oxidative stress. PMID:27869189

  9. Species-Specific Standard Redox Potential of Thiol-Disulfide Systems: A Key Parameter to Develop Agents against Oxidative Stress

    NASA Astrophysics Data System (ADS)

    Mirzahosseini, Arash; Noszál, Béla

    2016-11-01

    Microscopic standard redox potential, a new physico-chemical parameter was introduced and determined to quantify thiol-disulfide equilibria of biological significance. The highly composite, codependent acid-base and redox equilibria of thiols could so far be converted into pH-dependent, apparent redox potentials (E’°) only. Since the formation of stable metal-thiolate complexes precludes the direct thiol-disulfide redox potential measurements by usual electrochemical techniques, an indirect method had to be elaborated. In this work, the species-specific, pH-independent standard redox potentials of glutathione were determined primarily by comparing it to 1-methylnicotinamide, the simplest NAD+ analogue. Secondarily, the species-specific standard redox potentials of the two-electron redox transitions of cysteamine, cysteine, homocysteine, penicillamine, and ovothiol were determined using their microscopic redox equilibrium constants with glutathione. The 30 different, microscopic standard redox potential values show close correlation with the respective thiolate basicities and provide sound means for the development of potent agents against oxidative stress.

  10. Relationship Between Redox Potential, Disinfectant, and pH in Drinking Water

    EPA Science Inventory

    This work will examine the effects of pH and oxidant type (chlorine [Cl2], oxygen [O2], hydrogen peroxide [H2O2], monochloramine [MCA], and potassium permanganate [KMnO4]) and concentration (mg/L) on the redox potential of buffered test water. Also, the effects of incrementing ir...

  11. Influence of microbial growth in the redox potential of fermented cucumbers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Commonly, pH measurements are used during the production of fermented cucumbers to indirectly monitor growth of lactic acid bacteria (LAB) and acid production. Redox potential (Eh) measurements, which are determined by the flux of electrons in a system, could serve as a more accurate tool to monitor...

  12. Real-Time Imaging of the Intracellular Glutathione Redox Potential in the Malaria Parasite Plasmodium falciparum

    PubMed Central

    Kasozi, Denis; Mohring, Franziska; Rahlfs, Stefan; Meyer, Andreas J.; Becker, Katja

    2013-01-01

    In the malaria parasite Plasmodium falciparum, the cellular redox potential influences signaling events, antioxidant defense, and mechanisms of drug action and resistance. Until now, the real-time determination of the redox potential in malaria parasites has been limited because conventional approaches disrupt sub-cellular integrity. Using a glutathione biosensor comprising human glutaredoxin-1 linked to a redox-sensitive green fluorescent protein (hGrx1-roGFP2), we systematically characterized basal values and drug-induced changes in the cytosolic glutathione-dependent redox potential (EGSH) of drug-sensitive (3D7) and resistant (Dd2) P. falciparum parasites. Via confocal microscopy, we demonstrated that hGrx1-roGFP2 rapidly detects EGSH changes induced by oxidative and nitrosative stress. The cytosolic basal EGSH of 3D7 and Dd2 were estimated to be −314.2±3.1 mV and −313.9±3.4 mV, respectively, which is indicative of a highly reducing compartment. We furthermore monitored short-, medium-, and long-term changes in EGSH after incubation with various redox-active compounds and antimalarial drugs. Interestingly, the redox cyclers methylene blue and pyocyanin rapidly changed the fluorescence ratio of hGrx1-roGFP2 in the cytosol of P. falciparum, which can, however, partially be explained by a direct interaction with the probe. In contrast, quinoline and artemisinin-based antimalarial drugs showed strong effects on the parasites' EGSH after longer incubation times (24 h). As tested for various conditions, these effects were accompanied by a drop in total glutathione concentrations determined in parallel with alternative methods. Notably, the effects were generally more pronounced in the chloroquine-sensitive 3D7 strain than in the resistant Dd2 strain. Based on these results hGrx1-roGFP2 can be recommended as a reliable and specific biosensor for real-time spatiotemporal monitoring of the intracellular EGSH in P. falciparum. Applying this technique in further

  13. Redox potential dynamics in a grassed swale used for storage and treatment

    NASA Astrophysics Data System (ADS)

    Vorenhout, Michel; Boogaard, Floris Cornelis

    2016-04-01

    Treatment wetlands are used to remove pollutants from water. Most swales are designed to infiltrate stormwater into the subsurface. A combination of both functions can help to enhance water quality and reduce flooding risks in urban areas. The chemical forms and possible removal of pollutants such as nitrate and heavy metals in wetlands are highly dependent on the redox conditions. The redox conditions are expected to be highly dynamic and dependent on water levels and flow. We studied the correlation between these factors in an urban grassed swale system, and show that more factors play a role in these systems than water levels alone. The study system is located in the World Heritage site "Bryggen" in the city of Bergen, Norway. It consists of a series of SUDS, a socalled treatment train. The system is fed by storm water, which is at first stored in a rain garden then led to grassed swales. Water infiltrates into the subsurface in the swales. The reason for implementation of the system at this site is the protection of the highly organic archaeological layers at the site, which requires reduced conditions. Swales 1 and 2 were equipped with pressure loggers and multi-level redox and temperature probes (-2, -5, -10 and -20cm from surface). Redox and temperature probes were connected to a HYPNOS system. Measurements were taken for more than 1 year at 15 minute interval. A weather station supplemented the dataset with precipitation measurements. The redox potential in the swales show a strong correlation with water level. The regularly flooded swale 2 shows frequent anoxic events (Eh < 200mV) where as swale 1 shows oxic conditions (Eh = 650mV) throughout the same measurement period. Swale 1 has fewer flooding events than Swale 2 and a more coarse soil with less organic matter than swale 2. These redox results are as expected given the local conditions, and show that redox conditions are localised phenomena that depend on local soil conditions. Analysis of the redox

  14. In vitro Real-time Measurement of the Intra-bacterial Redox Potential

    PubMed Central

    van der Heijden, Joris; Finlay, B. Brett

    2016-01-01

    All bacteria that live in oxygenated environments have to deal with oxidative stress caused by some form of exogenous or endogenous reactive oxygen species (ROS) (Imlay, 2013). Large quantities of ROS damage DNA, lipids and proteins which can eventually lead to bacterial cell death (Imlay, 2013). In contrast, smaller quantities of ROS can play more sophisticated roles in cellular signalling pathways affecting almost every process in the bacterial cell e.g. metabolism, stress responses, transcription, protein synthesis, etc. Previously, inadequate analytical methods prevented appropriate analysis of the intra-bacterial redox potential. Herein, we describe a method for the measurement of real-time changes to the intra-bacterial redox potential using redox-sensitive GFP (roGFP2) (van der Heijden et al., 2015). The roGFP2 protein is engineered to contain specific cysteine residues that form an internal disulfide bridge upon oxidation which results in a slight shift in protein conformation (Hanson et al., 2004). This shift results in two distinct protein isoforms with different fluorescence excitation spectra after excitation at 405 nm and 480 nm respectively. Consequently, the corresponding 405/480 nm ratio can be used as a measure for the intra-bacterial redox potential. The ratio-metric analysis excludes variations due to differences in roGFP2 concentrations and since the conformational shift is reversible the system allows for measurement of oxidizing as well as reducing conditions. In this protocol we describe the system by measuring the intra-bacterial redox potential inside Salmonella typhimurium (S. typhimurium) however this system can be adjusted for use in other Gram-negative bacteria. PMID:27617271

  15. Evaluation of an amperometric glucose biosensor based on a ruthenium complex mediator of low redox potential.

    PubMed

    Yamamoto, Katsunobu; Zeng, Haisheng; Shen, Yi; Ahmed, Md Mahiuddin; Kato, Takeshi

    2005-06-15

    An amperometric glucose ring-disk biosensor based on a ruthenium complex mediator of low redox potential was fabricated and evaluated. This thin-layer radial flow microsensor (10mul) with ring-disk working electrode displayed remarkable amperometric sensitivity. For Ru(3)(mu(3)-O)(AcO)(6)(Py)(3)(ClO(4)) (Ru-Py), a trinuclear oxo-acetate bridged cluster, a reversible redox curve of low redox potential and narrow potential window (redox potentials were -0.190 and -0.106V versus Ag/AgCl wire, respectively) was observed, which is comparable to many reported mediators such as ferrocene derivatives and other ruthenium complexes. The glucose and hydrogen peroxide assays were carried out with this complex-modified electrode Ru-Py-HRP-GOx/Nafion. The sensitivity was obtained 24nA (15.4mAM(-1)cm(-2)) for 10muM glucose and 126 nA (160mAM(-1)cm(-2)) for 5muM H(2)O(2), respectively with a working potential at 0V versus Ag/AgCl. Ascorbic acid was studied as interference to the glucose assay. The application of 0V potential versus Ag/AgCl did not avoid the occurrence of the oxidation of ascorbic acid, however, the pre-coating of ascorbate oxidase on the disk part of the ring-disk working electrode efficiently pre-oxidized the ascorbic acid and hence eliminated its interference on the glucose response. The practical reliability was also evaluated by assaying the dialysate from the prefrontal cortex of Wistar rats.

  16. Determination of glutathione redox potential and pH value in subcellular compartments of malaria parasites.

    PubMed

    Mohring, Franziska; Rahbari, Mahsa; Zechmann, Bernd; Rahlfs, Stefan; Przyborski, Jude M; Meyer, Andreas J; Becker, Katja

    2017-03-01

    The malaria parasite Plasmodium falciparum is exposed to multiple sources of oxidative challenge during its complex life cycle in the Anopheles vector and its human host. In order to further elucidate redox-based parasite host cell interactions and mechanisms of drug action, we targeted the genetically encoded glutathione redox sensor roGFP2 coupled to human glutaredoxin 1 (roGFP2-hGrx1) as well as the ratiometric pH sensor pHluorin to the apicoplast and the mitochondrion of P. falciparum. Using live cell imaging, this allowed for the first time the determination of the pH values of the apicoplast (7.12±0.40) and mitochondrion (7.37±0.09) in the intraerythrocytic asexual stages of the parasite. Based on the roGFP2-hGrx1 signals, glutathione-dependent redox potentials of -267mV and -328mV, respectively, were obtained. Employing these novel tools, initial studies on the effects of redox-active agents and clinically employed antimalarial drugs were carried out on both organelles.

  17. A new synthesis route for Os-complex modified redox polymers for potential biofuel cell applications.

    PubMed

    Pöller, Sascha; Beyl, Yvonne; Vivekananthan, Jeevanthi; Guschin, Dmitrii A; Schuhmann, Wolfgang

    2012-10-01

    A new synthesis route for Os-complex modified redox polymers was developed. Instead of ligand exchange reactions for coordinative binding of suitable precursor Os-complexes at the polymer, Os-complexes already exhibiting the final ligand shell containing a suitable functional group were bound to the polymer via an epoxide opening reaction. By separation of the polymer synthesis from the ligand exchange reaction at the Os-complex, the modification of the same polymer backbone with different Os-complexes or the binding of the same Os-complex to a number of different polymer backbones becomes feasible. In addition, the Os-complex can be purified and characterized prior to its binding to the polymer. In order to further understand and optimize suitable enzyme/redox polymer systems concerning their potential application in biosensors or biofuel cells, a series of redox polymers was synthesized and used as immobilization matrix for Trametes hirsuta laccase. The properties of the obtained biofuel cell cathodes were compared with similar biocatalytic interfaces derived from redox polymers obtained via ligand exchange reaction of the parent Os-complex with a ligand integrated into the polymer backbone during the polymer synthesis.

  18. Reduction potentials of heterometallic manganese-oxido cubane complexes modulated by redox-inactive metals.

    PubMed

    Tsui, Emily Y; Agapie, Theodor

    2013-06-18

    Understanding the effect of redox-inactive metals on the properties of biological and heterogeneous water oxidation catalysts is important both fundamentally and for improvement of future catalyst designs. In this work, heterometallic manganese-oxido cubane clusters [MMn3O4] (M = Sr(2+), Zn(2+), Sc(3+), Y(3+)) structurally relevant to the oxygen-evolving complex (OEC) of photosystem II were prepared and characterized. The reduction potentials of these clusters and other related mixed metal manganese-tetraoxido complexes are correlated with the Lewis acidity of the apical redox-inactive metal in a manner similar to a related series of heterometallic manganese-dioxido clusters. The redox potentials of the [SrMn3O4] and [CaMn3O4] clusters are close, which is consistent with the observation that the OEC is functional only with one of these two metals. Considering our previous studies of [MMn3O2] moieties, the present results with more structurally accurate models of the OEC ([MMn3O4]) suggest a general relationship between the reduction potentials of heterometallic oxido clusters and the Lewis acidities of incorporated cations that applies to diverse structural motifs. These findings support proposals that one function of calcium in the OEC is to modulate the reduction potential of the cluster to allow electron transfer.

  19. Lid mobility in lipase SMG1 validated using a thiol/disulfide redox potential probe.

    PubMed

    Guo, Shaohua; Popowicz, Grzegorz Maria; Li, Daoming; Yuan, Dongjuan; Wang, Yonghua

    2016-05-01

    Most lipases possess a lid domain above the catalytic site that is responsible for their activation. Lipase SMG1 from Malassezia globose CBS 7966 (Malassezia globosa LIP1), is a mono- and diacylglycerol lipase with an atypical loop-like lid domain. Activation of SMG1 was proposed to be solely through a gating mechanism involving two residues (F278 and N102). However, through disulfide bond cross-linking of the lid, this study shows that full activation also requires mobility of the lid domain, contrary to a previous proposal. The newly introduced disulfide bond makes lipase SMG1 eligible as a ratiometric thiol/disulfide redox potential probe, when it is coupled with chromogenic substrates. This redox-switch lipase could also be of potential use in cascade biocatalysis.

  20. Ageing vessel configuration for continuous redox potential-controlled very-high-gravity fermentation.

    PubMed

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

    2011-01-01

    The development of continuous very-high-gravity (VHG) fermentation is hindered by ineffective glucose uptake in order to result in zero discharge in the effluent stream. To overcome the problem, we proposed a continuous redox potential-controlled fermentation configuration, consisting of a Chemostat vessel connected with two ageing vessels installed in parallel, and the relevant design criteria are also specified. The Chemostat vessel is subjected to redox potential control to maintain yeast viability, and the ageing vessels are used to completely utilize glucose before discharging to next process unit. Two ageing vessels are scheduled alternatively, resulting in continuously-like operation. The size of ageing vessel is governed by the Chemostat size, dilution rate and filling time. The guideline to choose proper dilution rate is provided and the selection criterion of the proposed continuous configuration over batch fermentation is derived. The excess ethanol produced by the proposed continuous configuration over batch fermenter is quantified. As an illustration, a bio-ethanol plant is typically operated 8000 h per annum and the downtime between batches is 6h. Given that the fermenter size of 100 m(3) for both batch fermenter and Chemostat vessel, and glucose fed at 300 g/l, if the proposed continuous redox potential-controlled fermentation configuration (operated at 0.028 h(-1) and controlled at -50 mV) is selected, it will take 191 h for this configuration to outperform the batch counterpart, and the excess amount of ethanol being produced will be 1142 t.

  1. Redox-Inactive Metals Modulate the Reduction Potential in Heterometallic Manganese-Oxido Clusters

    PubMed Central

    Tsui, Emily Y.; Tran, Rosalie; Yano, Junko; Agapie, Theodor

    2013-01-01

    Redox-inactive metals are found in biological and heterogeneous water oxidation catalysts, but their roles in catalysis are currently not well understood. A series of high oxidation state tetranuclear-dioxido clusters comprised of three manganese centers and a redox-inactive metal (M) of various charge is reported. Crystallographic studies show an unprecedented Mn3M(μ4-O)(μ2-O) core that remains intact upon changing M or the manganese oxidation state. Electrochemical studies reveal that the reduction potentials span a window of 700 mV, dependent upon the Lewis acidity of the second metal. With the pKa of the redox-inactive metal-aqua complex as a measure of Lewis acidity, these compounds display a linear dependence between reduction potential and acidity with a slope of ca. 100 mV per pKa unit. The Sr2+ and Ca2+ compounds show similar potentials, an observation that correlates with the behavior of the OEC, which is active only in the presence of one of these two metals. PMID:23511417

  2. Redox potentials of dopamine and its supramolecular complex with aspartic acid

    NASA Astrophysics Data System (ADS)

    Liu, Tao; Han, Ling-Li; Du, Chun-Mei; Yu, Zhang-Yu

    2014-07-01

    Dopamine (DA) can be oxidized to dopamine quinone (DAquinone) through a one-step, two-electron redox reaction. The electron transfer property of DA and its supramolecular complex with aspartic acid (Asp) has been investigated by the theoretical calculations. We calculated the standard redox potentials ( E o) of DA/DAquinone at the MP2/6-31G( d,p)//B3LYP/6-31G( d,p), MP2/6-31+G( d,p)//B3LYP/6-31+G( d,p), MP2/6-31G( d,p)//B3LYP/6-311G( d,p), and MP2/6-311+G( d,p)//B3LYP/6-311+G( d,p) levels. Comparing the experimental value, the redox potentials of DA/DAquinone obtained at MP2//B3LYP/6-311G( d,p) and MP2//B3LYP/6-311+G( d,p) levels can be considered as the upper and lower estimates. DA can form supramolecular complex (DA-Asp) with Asp through hydrogen bond (H-bond). Therefore, the values of 0.631 and 0.628 V obtained at MP2//B3LYP/6-311G( d,p) and MP2//B3LYP/6-311+G( d,p) levels for DA-Asp/DAquinone-Asp can be proposed as the upper and lower estimates of a probable (about 0.630 V) value of the corresponding redox potential. The calculated E o values of DA-Asp/DAquinone-Asp at the four theoretical levels are upper than those of DA/DAquinone, which indicates that the formation of H-bonds weaken the electron-donating ability of DA.

  3. An Inner Membrane Cytochrome Required Only for Reduction of High Redox Potential Extracellular Electron Acceptors

    PubMed Central

    Levar, Caleb E.; Chan, Chi Ho; Mehta-Kolte, Misha G.

    2014-01-01

    ABSTRACT Dissimilatory metal-reducing bacteria, such as Geobacter sulfurreducens, transfer electrons beyond their outer membranes to Fe(III) and Mn(IV) oxides, heavy metals, and electrodes in electrochemical devices. In the environment, metal acceptors exist in multiple chelated and insoluble forms that span a range of redox potentials and offer different amounts of available energy. Despite this, metal-reducing bacteria have not been shown to alter their electron transfer strategies to take advantage of these energy differences. Disruption of imcH, encoding an inner membrane c-type cytochrome, eliminated the ability of G. sulfurreducens to reduce Fe(III) citrate, Fe(III)-EDTA, and insoluble Mn(IV) oxides, electron acceptors with potentials greater than 0.1 V versus the standard hydrogen electrode (SHE), but the imcH mutant retained the ability to reduce Fe(III) oxides with potentials of ≤−0.1 V versus SHE. The imcH mutant failed to grow on electrodes poised at +0.24 V versus SHE, but switching electrodes to −0.1 V versus SHE triggered exponential growth. At potentials of ≤−0.1 V versus SHE, both the wild type and the imcH mutant doubled 60% slower than at higher potentials. Electrodes poised even 100 mV higher (0.0 V versus SHE) could not trigger imcH mutant growth. These results demonstrate that G. sulfurreducens possesses multiple respiratory pathways, that some of these pathways are in operation only after exposure to low redox potentials, and that electron flow can be coupled to generation of different amounts of energy for growth. The redox potentials that trigger these behaviors mirror those of metal acceptors common in subsurface environments where Geobacter is found. PMID:25425235

  4. An inner membrane cytochrome required only for reduction of high redox potential extracellular electron acceptors

    SciTech Connect

    Levar, Caleb E.; Chan, Chi Ho; Mehta-Kolte, Misha G.; Bond, Daniel R.

    2014-10-28

    Dissimilatory metal-reducing bacteria, such as Geobacter sulfurreducens, transfer electrons beyond their outer membranes to Fe(III) and Mn(IV) oxides, heavy metals, and electrodes in electrochemical devices. In the environment, metal acceptors exist in multiple chelated and insoluble forms that span a range of redox potentials and offer different amounts of available energy. Despite this, metal-reducing bacteria have not been shown to alter their electron transfer strategies to take advantage of these energy differences. Disruption of imcH, encoding an inner membrane c-type cytochrome, eliminated the ability of G. sulfurreducens to reduce Fe(III) citrate, Fe(III)-EDTA, and insoluble Mn(IV) oxides, electron acceptors with potentials greater than 0.1 V versus the standard hydrogen electrode (SHE), but the imcH mutant retained the ability to reduce Fe(III) oxides with potentials of ≤–0.1 V versus SHE. The imcH mutant failed to grow on electrodes poised at +0.24 V versus SHE, but switching electrodes to –0.1 V versus SHE triggered exponential growth. At potentials of ≤–0.1 V versus SHE, both the wild type and the imcH mutant doubled 60% slower than at higher potentials. Electrodes poised even 100 mV higher (0.0 V versus SHE) could not trigger imcH mutant growth. These results demonstrate that G. sulfurreducens possesses multiple respiratory pathways, that some of these pathways are in operation only after exposure to low redox potentials, and that electron flow can be coupled to generation of different amounts of energy for growth. Redox potentials that trigger these behaviors mirror those of metal acceptors common in subsurface environments where Geobacter is found.

  5. Reactions of copper macrocycles with antioxidants and HOCl: potential for biological redox sensing.

    PubMed

    Sowden, Rebecca J; Trotter, Katherine D; Dunbar, Lynsey; Craig, Gemma; Erdemli, Omer; Spickett, Corinne M; Reglinski, John

    2013-02-01

    A series of simple copper N(2)S(2) macrocycles were examined for their potential as biological redox sensors, following previous characterization of their redox potentials and crystal structures. The divalent species were reduced by glutathione or ascorbate at a biologically relevant pH in aqueous buffer. A less efficient reduction was also achieved by vitamin E in DMSO. Oxidation of the corresponding univalent copper species by sodium hypochlorite resulted in only partial (~65 %) recovery of the divalent form. This was concluded to be due to competition between metal oxidation and ligand oxidation, which is believed to contribute to macrocycle demetallation. Electrospray mass spectrometry confirmed that ligand oxidation had occurred. Moreover, the macrocyclic complexes could be demetallated by incubation with EDTA and bovine serum albumin, demonstrating that they would be inappropriate for use in biological systems. The susceptibility to oxidation and demetallation was hypothesized to be due to oxidation of the secondary amines. Consequently these were modified to incorporate additional oxygen donor atoms. This modification led to greater resistance to demetallation and ligand oxidation, providing a better platform for further development of copper macrocycles as redox sensors for use in biological systems.

  6. Early-Late Heterobimetallic Complexes Linked by Phosphinoamide Ligands. Tuning Redox Potentials and Small Molecule Activation

    SciTech Connect

    Thomas, Christine M.

    2015-08-01

    Recent attention in the chemical community has been focused on the energy efficient and environmentally benign conversion of abundant small molecules (CO2, H2O, etc.) to useful liquid fuels. This project addresses these goals by examining fundamental aspects of catalyst design to ultimately access small molecule activation processes under mild conditions. Specifically, Thomas and coworkers have targetted heterobimetallic complexes that feature metal centers with vastly different electronic properties, dictated both by their respective positions on the periodic table and their coordination environment. Unlike homobimetallic complexes featuring identical or similar metals, the bonds between metals in early/late heterobimetallics are more polarized, with the more electron-rich late metal center donating electron density to the more electron-deficient early metal center. While metal-metal bonds pose an interesting strategy for storing redox equivalents and stabilizing reactive metal fragments, the polar character of metal-metal bonds in heterobimetallic complexes renders these molecules ideally poised to react with small molecule substrates via cleavage of energy-rich single and double bonds. In addition, metal-metal interactions have been shown to dramatically affect redox potentials and promote multielectron redox activity, suggesting that metal-metal interactions may provide a mechanism to tune redox potentials and access substrate reduction/activation at mild overpotentials. This research project has provided a better fundamental understanding of how interactions between transition metals can be used as a strategy to promote and/or control chemical transformations related to the clean production of fuels. While this project focused on the study of homogeneous systems, it is anticipated that the broad conclusions drawn from these investigations will be applicable to heterogeneous catalysis as well, particularly on heterogeneous processes that occur at interfaces in

  7. An inner membrane cytochrome required only for reduction of high redox potential extracellular electron acceptors

    DOE PAGES

    Levar, Caleb E.; Chan, Chi Ho; Mehta-Kolte, Misha G.; ...

    2014-10-28

    Dissimilatory metal-reducing bacteria, such as Geobacter sulfurreducens, transfer electrons beyond their outer membranes to Fe(III) and Mn(IV) oxides, heavy metals, and electrodes in electrochemical devices. In the environment, metal acceptors exist in multiple chelated and insoluble forms that span a range of redox potentials and offer different amounts of available energy. Despite this, metal-reducing bacteria have not been shown to alter their electron transfer strategies to take advantage of these energy differences. Disruption of imcH, encoding an inner membrane c-type cytochrome, eliminated the ability of G. sulfurreducens to reduce Fe(III) citrate, Fe(III)-EDTA, and insoluble Mn(IV) oxides, electron acceptors with potentialsmore » greater than 0.1 V versus the standard hydrogen electrode (SHE), but the imcH mutant retained the ability to reduce Fe(III) oxides with potentials of ≤–0.1 V versus SHE. The imcH mutant failed to grow on electrodes poised at +0.24 V versus SHE, but switching electrodes to –0.1 V versus SHE triggered exponential growth. At potentials of ≤–0.1 V versus SHE, both the wild type and the imcH mutant doubled 60% slower than at higher potentials. Electrodes poised even 100 mV higher (0.0 V versus SHE) could not trigger imcH mutant growth. These results demonstrate that G. sulfurreducens possesses multiple respiratory pathways, that some of these pathways are in operation only after exposure to low redox potentials, and that electron flow can be coupled to generation of different amounts of energy for growth. Redox potentials that trigger these behaviors mirror those of metal acceptors common in subsurface environments where Geobacter is found.« less

  8. Redox potential of shallow groundwater by 1-month continuous in situ potentiometric measurements

    NASA Astrophysics Data System (ADS)

    Ioka, Seiichiro; Muraoka, Hirofumi; Suzuki, Yota

    2016-06-01

    One-month continuous in situ potentiometric measurements of redox potential (Eh) were used to investigate the dominant redox processes in the shallow groundwater (i.e., <10 m) of a Holocene aquifer, Aomori City, northern Japan. The Eh values, which were determined using a platinum electrode, were -163, -169 and -173 mV, respectively, for three monitoring campaigns. The temperatures and pH values of shallow groundwater during all three periods were approximately 12 °C and 6.6, respectively. Dissolved oxygen and sulfide ion concentrations were not detected. Chemical analyses showed that the shallow groundwater is Na-Fe-HCO3 type, and contains over 40 mg/L of Fe (the dominant cation) and over 200 mg/L of HCO3 - (the dominant anion). A good fit was found between measured Eh values and Eh values calculated using thermodynamic data of fine-grained goethite. This suggests that Fe redox system is related to the Eh values of shallow groundwater in the Aomori City aquifer.

  9. Redox Potential as a Means to Control the Treatment of Slurry to Lower H2S Emissions

    PubMed Central

    Hjorth, Maibritt; Pedersen, Christina Ø; Feilberg, Anders

    2012-01-01

    Slurry can be oxidized to eliminate undesirable emissions, including malodorous hydrogen sulfide (H2S). However, it is difficult to assess the optimal amount of oxidizing agent required. In this study, one cow and one pig manure, each in three particle size ranges were oxidized with 0–350 mg ozone/L manure. Redox and H2S concentration were measured continuously. During ozonation the manures gave equivalent redox potential curves. A relatively rapid rise in redox potential was observed within a range of −275 mV to −10 mV, with all manures changing as a minimum from −200 mV to −80 mV. The gaseous H2S emissions were decreased by 99.5% during the redox increase (−200 mV to −80 mV). This is attributed to H2S oxidation by ozone and oxygen, and is not due to H2S deprotonation or gas flushing. By identifying the initiation of the final redox level following the rise, the amount of ozone required to remove H2S from the manure samples was estimated to be in the range of 6–24 mg O3/L manure, depending on the type of manure. Hence, continuous monitoring of redox potential (termination of the redox rise) during the oxidation treatment is a simple method of achieving cost-effective minimization of H2S emissions from slurry. PMID:22778588

  10. The effect of HWVP feed nitrate and carbonate content on glass redox adjustment

    SciTech Connect

    Wiemers, K.D.

    1996-03-01

    The Hanford Waste Vitrification Plant (HWVP) is being designed for the Department of Energy to immobilize pretreated radioactive high-level waste (HLW) as glass for geological disposal. In the HWVP formic acid will be added to the pretreated HLW prior to vitrification. The formic acid is added to adjust the feed rheology and to provide a reductant which maintains the feed in the melter within an acceptable redox range. This study was conducted to evaluate the effect of nitrate and carbonate concentrations in the pretreated neutralized current acid waste (NCAW) feed on the amount of formic acid required to obtain an acceptable glass redox state in the melter. The glass redox state was measured by the Fe{sup +2}/Fe{sup +3} ratio in the vitrified product.

  11. Complex oscillatory redox dynamics with signaling potential at the edge between normal and pathological mitochondrial function

    PubMed Central

    Kembro, Jackelyn M.; Cortassa, Sonia; Aon, Miguel A.

    2014-01-01

    The time-keeping properties bestowed by oscillatory behavior on functional rhythms represent an evolutionarily conserved trait in living systems. Mitochondrial networks function as timekeepers maximizing energetic output while tuning reactive oxygen species (ROS) within physiological levels compatible with signaling. In this work, we explore the potential for timekeeping functions dependent on mitochondrial dynamics with the validated two-compartment mitochondrial energetic-redox (ME-R) computational model, that takes into account (a) four main redox couples [NADH, NADPH, GSH, Trx(SH)2], (b) scavenging systems (glutathione, thioredoxin, SOD, catalase) distributed in matrix and extra-matrix compartments, and (c) transport of ROS species between them. Herein, we describe that the ME-R model can exhibit highly complex oscillatory dynamics in energetic/redox variables and ROS species, consisting of at least five frequencies with modulated amplitudes and period according to power spectral analysis. By stability analysis we describe that the extent of steady state—as against complex oscillatory behavior—was dependent upon the abundance of Mn and Cu, Zn SODs, and their interplay with ROS production in the respiratory chain. Large parametric regions corresponding to oscillatory dynamics of increasingly complex waveforms were obtained at low Cu, Zn SOD concentration as a function of Mn SOD. This oscillatory domain was greatly reduced at higher levels of Cu, Zn SOD. Interestingly, the realm of complex oscillations was located at the edge between normal and pathological mitochondrial energetic behavior, and was characterized by oxidative stress. We conclude that complex oscillatory dynamics could represent a frequency- and amplitude-modulated H2O2 signaling mechanism that arises under intense oxidative stress. By modulating SOD, cells could have evolved an adaptive compromise between relative constancy and the flexibility required under stressful redox

  12. Metabolic efficiency of Geobacter sulfurreducens growing on anodes with different redox potentials.

    PubMed

    Bosch, Julian; Lee, Keun-Young; Hong, Siang-Fu; Harnisch, Falk; Schröder, Uwe; Meckenstock, Rainer U

    2014-06-01

    Microorganisms respiring Fe(III) in the environment face a range of redox potentials of the prospective terminal ferric electron acceptors, because Fe(III) can be present in different minerals or organic complexes. We investigated the adaptation of Geobacter sulfurreducens to this range by exposing the bacteria to different redox potentials between the electron donor acetate and solid, extracellular anodes in a microbial fuel-cell set-up. Over a range of anode potentials from -0.105 to +0.645 V versus standard hydrogen electrode, G. sulfurreducens produced identical amounts of biomass per electron respired. This indicated that the organism cannot utilize higher available energies for energy conservation to ATP, and confirmed recent studies. Either the high potentials cannot be used due to physiological limitations, or G. sulfurreducens decreased its metabolic efficiency, and less biomass per unit of energy was produced. In this case, G. sulfurreducens "wasted" energy at high-potential differences, most likely as heat to fuel growth kinetics.

  13. Chemical and structural indicators for large redox potentials in Fe-based positive electrode materials.

    PubMed

    Melot, Brent C; Scanlon, David O; Reynaud, Marine; Rousse, Gwenaëlle; Chotard, Jean-Noël; Henry, Marc; Tarascon, Jean-Marie

    2014-07-23

    Li-ion batteries have enabled a revolution in the way portable consumer-electronics are powered and will play an important role as large-scale electrochemical storage applications like electric vehicles and grid-storage are developed. The ability to identify and design promising new positive insertion electrodes will be vital in continuing to push Li-ion technology to its fullest potential. Utilizing a combination of computational tools and structural analysis, we report new indicators which will facilitate the recognition of phases with the desired redox potential. Most importantly of these, we find there is a strong correlation between the presence of Li ions sitting in close-proximity to the redox center of polyanionic phases and the open circuit voltage in Fe-based cathodes. This common structural feature suggests that the bonding associated with Li may have a secondary inductive effect which increases the ionic character of Fe bonds beyond what is typically expected based purely on arguments of electronegativity associated with the polyanionic group. This correlation is supported by ab initio calculations which show the Bader charge increases (reflecting an increased ionicity) in a nearly linear fashion with the experimental cell potentials. These features are demonstrated to be consistent across a wide variety of compositions and structures and should help to facilitate the design of new, high-potential, and environmentally sustainable insertion electrodes.

  14. 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.

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

    PubMed

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

    2017-01-01

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

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

    PubMed Central

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

    2017-01-01

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

  17. Designing redox potential-controlled protein switches based on mutually exclusive proteins.

    PubMed

    Peng, Qing; Kong, Na; Wang, Hui-Chuan Eileen; Li, Hongbin

    2012-08-01

    Synthetic/artificial protein switches provide an efficient means of controlling protein functions using chemical signals and stimuli. Mutually exclusive proteins, in which only the host or guest domain can remain folded at a given time owing to conformational strain, have been used to engineer novel protein switches that can switch enzymatic functions on and off in response to ligand binding. To further explore the potential of mutually exclusive proteins as protein switches and sensors, we report here a new redox-based approach to engineer a mutually exclusive folding-based protein switch. By introducing a disulfide bond into the host domain of a mutually exclusive protein, we demonstrate that it is feasible to use redox potential to switch the host domain between its folded and unfolded conformations via the mutually exclusive folding mechanism, and thus switching the functionality of the host domain on and off. Our study opens a new and potentially general avenue that uses mutually exclusive proteins to design novel switches able to control the function of a variety of proteins.

  18. Correlation between the stability and redox potential of three homologous cytochromes c from two thermophiles and one mesophile.

    PubMed

    Takeda, Taku; Sonoyama, Takafumi; Takayama, Shin-ichi J; Mita, Hajime; Yamamoto, Yasuhiko; Sambongi, Yoshihiro

    2009-02-01

    The stability of the oxidized and reduced forms of three homologous cytochromes c from two thermophiles and one mesophile was systematically monitored by means of Soret absorption measurements in the presence of various concentrations of a denaturant, guanidine thiocyanate, at pH 7.0 at 25 degrees C. Thermophilic Hydrogenobacter thermophilus cytochrome c(552) was the most stable in both redox states, followed by moderately thermophilic Hydrogenophilus thermoluteolus cytochrome c(552), and then mesophilic Pseudomonas aeruginosa cytochrome c(551). Further stability and electrochemical analysis of the three proteins and the reciprocal variants, which exhibited a different hydrophobic interaction with the heme, showed that the one with the higher stability in both redox states had the lower redox potential. Consequently, these cytochromes c probably adapted to the cellular environments of the original bacteria with correlated stability and redox potential constraints, which are in part regulated by the hydrophobicity around the heme.

  19. Redox potential as a master variable controlling pathways of metal reduction by Geobacter sulfurreducens

    PubMed Central

    Levar, Caleb E; Hoffman, Colleen L; Dunshee, Aubrey J; Toner, Brandy M; Bond, Daniel R

    2017-01-01

    Geobacter sulfurreducens uses at least two different pathways to transport electrons out of the inner membrane quinone pool before reducing acceptors beyond the outer membrane. When growing on electrodes poised at oxidizing potentials, the CbcL-dependent pathway operates at or below redox potentials of –0.10 V vs the standard hydrogen electrode, whereas the ImcH-dependent pathway operates only above this value. Here, we provide evidence that G. sulfurreducens also requires different electron transfer proteins for reduction of a wide range of Fe(III)- and Mn(IV)-(oxyhydr)oxides, and must transition from a high- to low-potential pathway during reduction of commonly studied soluble and insoluble metal electron acceptors. Freshly precipitated Fe(III)-(oxyhydr)oxides could not be reduced by mutants lacking the high-potential pathway. Aging these minerals by autoclaving did not change their powder X-ray diffraction pattern, but restored reduction by mutants lacking the high-potential pathway. Mutants lacking the low-potential, CbcL-dependent pathway had higher growth yields with both soluble and insoluble Fe(III). Together, these data suggest that the ImcH-dependent pathway exists to harvest additional energy when conditions permit, and CbcL switches on to allow respiration closer to thermodynamic equilibrium conditions. With evidence of multiple pathways within a single organism, the study of extracellular respiration should consider not only the crystal structure or solubility of a mineral electron acceptor, but rather the redox potential, as this variable determines the energetic reward affecting reduction rates, extents, and final microbial growth yields in the environment. PMID:28045456

  20. Redox potential as a master variable controlling pathways of metal reduction by Geobacter sulfurreducens.

    PubMed

    Levar, Caleb E; Hoffman, Colleen L; Dunshee, Aubrey J; Toner, Brandy M; Bond, Daniel R

    2017-03-01

    Geobacter sulfurreducens uses at least two different pathways to transport electrons out of the inner membrane quinone pool before reducing acceptors beyond the outer membrane. When growing on electrodes poised at oxidizing potentials, the CbcL-dependent pathway operates at or below redox potentials of -0.10 V vs the standard hydrogen electrode, whereas the ImcH-dependent pathway operates only above this value. Here, we provide evidence that G. sulfurreducens also requires different electron transfer proteins for reduction of a wide range of Fe(III)- and Mn(IV)-(oxyhydr)oxides, and must transition from a high- to low-potential pathway during reduction of commonly studied soluble and insoluble metal electron acceptors. Freshly precipitated Fe(III)-(oxyhydr)oxides could not be reduced by mutants lacking the high-potential pathway. Aging these minerals by autoclaving did not change their powder X-ray diffraction pattern, but restored reduction by mutants lacking the high-potential pathway. Mutants lacking the low-potential, CbcL-dependent pathway had higher growth yields with both soluble and insoluble Fe(III). Together, these data suggest that the ImcH-dependent pathway exists to harvest additional energy when conditions permit, and CbcL switches on to allow respiration closer to thermodynamic equilibrium conditions. With evidence of multiple pathways within a single organism, the study of extracellular respiration should consider not only the crystal structure or solubility of a mineral electron acceptor, but rather the redox potential, as this variable determines the energetic reward affecting reduction rates, extents, and final microbial growth yields in the environment.

  1. Variation of fermentation redox potential during cell-recycling continuous ethanol operation.

    PubMed

    Thani, Arthit; Lin, Yen-Han; Laopaiboon, Pattana; Laopaiboon, Lakkana

    2016-12-10

    Fermentation redox potential was monitored during cell-recycling continuous ethanol operation. The cell-recycling system (CRS) was operated using two hollow fibre (HF) membranes (pore sizes 0.20 and 0.65μm) at three dilution rates (0.02, 0.04 and 0.08h(-1)). Saccharomyces cerevisiae NP 01 were recycled in the fermenter at a recycle ratio of 0.625. Aeration was provided at 2.5vvm for the first 4h and then further supplied continuously at 0.25vvm. As steady state was established, results showed that the fermentation redox potential was lower for processes employing CRS than those without. At the same dilution rates, the sugar utilization and ethanol production with CRS were higher than those without CRS. The highest fermentation efficiency (87.94g/l of ethanol, ∼90% of theoretical yield) was achieved using a 0.2-μm HF membrane CRS at a dilution rate of 0.02h(-1). It was found that 7.53-10.07% of the carbon derived from glucose was incorporated into the yeast. Further, at the same dilution rates, yeast in the processes with CRS incorporated less carbon into ethanol than in those grown without CRS. This result suggests that processes involving CRS utilize more carbon for metabolite synthesis than biomass formation. This indicated that the processes with CRS could utilize more carbon for metabolite synthesis than biomass formation.

  2. Cell surface redox potential as a mechanism of defense against photosensitizers in fungi.

    PubMed

    Sollod, C C; Jenns, A E; Daub, M E

    1992-02-01

    The phytotoxin cercosporin, a singlet oxygen-generating photosensitizer, is toxic to plants, mice, and many fungi, yet the fungi that produce it, Cercospora spp., are resistant. We hypothesize that resistance to cercosporin may result from a reducing environment at the cell surface. Twenty tetrazolium dyes differing in redox potential were used as indicators of cell surface redox potential of seven fungal species differing in resistance to cercosporin. Resistant fungi were able to reduce significantly more dyes than were sensitive fungi. A correlation between dye reduction and cercosporin resistance was also observed when resistance levels of Cercospora species were manipulated by growth on different media. The addition of the reducing agents ascorbate, cysteine, and reduced glutathione (GSH) to growth media decreased cercosporin toxicity for sensitive fungi. None of these agents directly reduced cercosporin at the concentrations at which they protected fungi. Spectral and thin-layer chromatographic analyses of cercosporin solutions containing the different reducing agents indicated that GSH, but not cysteine or ascorbate, reacted with cercosporin. Resistant and sensitive fungi did not differ in endogenous levels of cysteine, GSH, or total thiols. On the basis of data from this and other studies, this report presents a model which proposes that cercosporin resistance results from the production of reducing power at the surfaces of resistant cells, leading to transient reduction and detoxification of the cercosporin molecule.

  3. Redox probing study of the potential dependence of charge transport through Li2O2

    DOE PAGES

    Knudsen, Kristian B.; Luntz, Alan C.; Jensen, Søren H.; ...

    2015-11-20

    In the field of energy storage devices the pursuit for cheap, high energy density, reliable secondary batteries is at the top of the agenda. The Li–O2 battery is one of the possible technologies that, in theory, should be able to close the gap, which exists between the present state-of-the-art Li-ion technologies and the demand placed on batteries by technologies such as electrical vehicles. Here we present a redox probing study of the charge transfer across the main deposition product lithium peroxide, Li2O2, in the Li–O2 battery using outer-sphere redox shuttles. The change in heterogeneous electron transfer exchange rate as amore » function of the potential and the Li2O2 layer thickness (~depth-of-discharge) was determined using electrochemical impedance spectroscopy. In addition, the attenuation of the electron transfer exchange rate with film thickness is dependent on the probing potential, providing evidence that hole transport is the dominant process for charge transfer through Li2O2 and showing that the origin of the sudden death observed upon discharge is due to charge transport limitations.« less

  4. Modulating the Redox Potential of the Stable Electron Acceptor, QB, in Mutagenized Photosystem II Reaction Centers.

    SciTech Connect

    Perrine, Zoee; Sayre, Richard

    2011-02-10

    One of the unique features of electron transfer processes in photosystem II (PSII) reaction centers (RC) is the exclusive transfer of electrons down only one of the two parallel cofactor branches. In contrast to the RC core polypeptides (psaA and psaB) of photosystem I (PSI), where electron transfer occurs down both parallel redox-active cofactor branches, there is greater protein-cofactor asymmetry between the PSII RC core polypeptides (D1 and D2). We have focused on the identification of protein-cofactor relationships that determine the branch along which primary charge separation occurs (P680+/pheophytin-(Pheo)). We have previously shown that mutagenesis of the strong hydrogen-bonding residue, D1-E130, to less polar residues (D1-E130Q,H,L) shifted the midpoint potential of the PheoD1/PheoD1- couple to more negative values, reducing the quantum yield of primary charge separation. We did not observe, however, electron transfer down the inactive branch in D1-E130 mutants. The protein residue corresponding to D1-E130 on the inactive branch is D2-Q129 which presumably has a reduced hydrogen-bonding interaction with PheoD2 relative to the D1-E130 residue with PheoD1. Analysis of the recent 2.9 Å cyanobacterial PSII crystal structure indicated, however, that the D2-Q129 residue was too distant from the PheoD2 headgroup to serve as a possible hydrogen bond donor and directly impact its midpoint potential as well as potentially determine the directionality of electron transfer. Our objective was to characterize the function of this highly conserved inactive branch residue by replacing it with a nonconservative leucine or a conservative histidine residue. Measurements of Chl fluorescence decay kinetics and thermoluminescence studies indicate that the mutagenesis of D2-Q129 decreases the redox gap between QA and QB due to a lowering of the redox potential of QB. The

  5. Redox potential characterization and soil greenhouse gas concentration across a hydrological gradient in a Gulf coast forest

    USGS Publications Warehouse

    Yu, K.; Faulkner, S.P.; Patrick, W.H.

    2006-01-01

    Soil redox potential (Eh), concentrations of oxygen (O2) and three greenhouse gases (CO2, CH4, and N2O) were measured in the soil profile of a coastal forest at ridge, transition, and swamp across a hydrological gradient. The results delineated a distinct boundary in soil Eh and O2 concentration between the ridge and swamp with essentially no overlap between the two locations. Critical soil Eh to initiate significant CH4 production under this field conditions was about +300 mV, much higher than in the homogenous soils (about -150 mV). The strength of CH4 source to the atmosphere was strong for the swamp, minor for the transition, and negligible or even negative (consumption) for the ridge. Maximum N2O concentration in the soils was found at about Eh +250 mV, and the soil N2O emission was estimated to account for less than 4% for the ridge and transition, and almost negligible for the swamp in the cumulative global warming potential (GWP) of these three gases. The dynamic nature of this study site in response to water table fluctuations across a hydrological gradient makes it an ideal model of impact of future sea level rise to coastal ecosystems. Soil carbon (C) sequestration potential due to increasing soil water content upon sea level rise and subsidence in this coastal forest was likely limited and temporal, and at the expense of increasing soil CH4 production and emission. ?? 2005 Elsevier Ltd. All rights reserved.

  6. Opening of connexin 43 hemichannels is increased by lowering intracellular redox potential

    PubMed Central

    Retamal, Mauricio A.; Schalper, Kurt A.; Shoji, Kenji F.; Bennett, Michael V. L.; Sáez, Juan C.

    2007-01-01

    Nonjunctional membrane in many cells contains connexin gap junction hemichannels (or connexons) that can open to allow permeation of small molecules. Opening of Cx43 hemichannels is infrequent in normal extracellular Ca2+ and enhanced by low Ca2+, positive membrane potentials, and dephosphorylation of critical residues. Here we report that lowering intracellular redox potential increases Cx43 hemichannel open probability under otherwise normal conditions. We studied dye uptake and single-channel activity in HeLa cells transfected with wild-type Cx43, Cx43 with enhanced GFP attached to its C terminus (Cx43-EGFP), and Cx43 with enhanced GFP attached to its N terminus (EGFP-Cx43). Dithiothreitol [(DTT) 10 mM], a membrane permeant-reducing agent, increased the rate of dye uptake by cells expressing Cx43 and Cx43-EGFP, but not by parental cells or cells expressing EGFP-Cx43. Induced dye uptake was blocked by La3+, by a peptide gap junction and hemichannel blocker (gap 26), and by flufenamic acid. DTT increased Cx43-EGFP hemichannel opening at positive voltages. Bath application of reduced glutathione, a membrane impermeant-reducing agent, did not increase dye uptake, but glutathione in the recording pipette increased hemichannel opening at positive voltages, suggesting that it acted intracellularly. DTT caused little change in levels of surface Cx43 or Cx43-EGFP, or in intracellular pH. These findings suggest that lowering intracellular redox potential increases the opening of Cx43 and Cx43-EGFP hemichannels, possibly by action on cytoplasmic cysteine residues in the connexin C terminus. PMID:17494739

  7. Opening of connexin 43 hemichannels is increased by lowering intracellular redox potential.

    PubMed

    Retamal, Mauricio A; Schalper, Kurt A; Shoji, Kenji F; Bennett, Michael V L; Sáez, Juan C

    2007-05-15

    Nonjunctional membrane in many cells contains connexin gap junction hemichannels (or connexons) that can open to allow permeation of small molecules. Opening of Cx43 hemichannels is infrequent in normal extracellular Ca(2+) and enhanced by low Ca(2+), positive membrane potentials, and dephosphorylation of critical residues. Here we report that lowering intracellular redox potential increases Cx43 hemichannel open probability under otherwise normal conditions. We studied dye uptake and single-channel activity in HeLa cells transfected with wild-type Cx43, Cx43 with enhanced GFP attached to its C terminus (Cx43-EGFP), and Cx43 with enhanced GFP attached to its N terminus (EGFP-Cx43). Dithiothreitol [(DTT) 10 mM], a membrane permeant-reducing agent, increased the rate of dye uptake by cells expressing Cx43 and Cx43-EGFP, but not by parental cells or cells expressing EGFP-Cx43. Induced dye uptake was blocked by La(3+), by a peptide gap junction and hemichannel blocker (gap 26), and by flufenamic acid. DTT increased Cx43-EGFP hemichannel opening at positive voltages. Bath application of reduced glutathione, a membrane impermeant-reducing agent, did not increase dye uptake, but glutathione in the recording pipette increased hemichannel opening at positive voltages, suggesting that it acted intracellularly. DTT caused little change in levels of surface Cx43 or Cx43-EGFP, or in intracellular pH. These findings suggest that lowering intracellular redox potential increases the opening of Cx43 and Cx43-EGFP hemichannels, possibly by action on cytoplasmic cysteine residues in the connexin C terminus.

  8. Differentiation of chemical reaction activity of various carbon nanotubes using redox potential: Classification by physical and chemical structures.

    PubMed

    Tsuruoka, Shuji; Matsumoto, Hidetoshi; Castranova, Vincent; Porter, Dale W; Yanagisawa, Takashi; Saito, Naoto; Kobayashi, Shinsuke; Endo, Morinobu

    2015-12-01

    The present study systematically examined the kinetics of a hydroxyl radical scavenging reaction of various carbon nanotubes (CNTs) including double-walled and multi-walled carbon nanotubes (DWCNTs and MWCNTs), and carbon nano peapods (AuCl3@DWCNT). The theoretical model that we recently proposed based on the redox potential of CNTs was used to analyze the experimental results. The reaction kinetics for DWCNTs and thin MWCNTs agreed well with the theoretical model and was consistent with each other. On the other hand, thin and thick MWCNTs behaved differently, which was consistent with the theory. Additionally, surface morphology of CNTs substantially influenced the reaction kinetics, while the doped particles in the center hollow parts of CNTs (AuCl3@DWCNT) shifted the redox potential in a different direction. These findings make it possible to predict the chemical and biological reactivity of CNTs based on the structural and chemical nature and their influence on the redox potential.

  9. Differentiation of chemical reaction activity of various carbon nanotubes using redox potential: Classification by physical and chemical structures

    PubMed Central

    Castranova, Vincent; Porter, Dale W.; Yanagisawa, Takashi; Saito, Naoto; Kobayashi, Shinsuke; Endo, Morinobu

    2016-01-01

    The present study systematically examined the kinetics of a hydroxyl radical scavenging reaction of various carbon nanotubes (CNTs) including double-walled and multi-walled carbon nanotubes (DWCNTs and MWCNTs), and carbon nano peapods (AuCl3@DWCNT). The theoretical model that we recently proposed based on the redox potential of CNTs was used to analyze the experimental results. The reaction kinetics for DWCNTs and thin MWCNTs agreed well with the theoretical model and was consistent with each other. On the other hand, thin and thick MWCNTs behaved differently, which was consistent with the theory. Additionally, surface morphology of CNTs substantially influenced the reaction kinetics, while the doped particles in the center hollow parts of CNTs (AuCl3@DWCNT) shifted the redox potential in a different direction. These findings make it possible to predict the chemical and biological reactivity of CNTs based on the structural and chemical nature and their influence on the redox potential. PMID:26783369

  10. Low glutathione regulates gene expression and the redox potentials of the nucleus and cytosol in Arabidopsis thaliana.

    PubMed

    Schnaubelt, Daniel; Queval, Guillaume; Dong, Yingping; Diaz-Vivancos, Pedro; Makgopa, Matome Eugene; Howell, Gareth; De Simone, Ambra; Bai, Juan; Hannah, Matthew A; Foyer, Christine H

    2015-02-01

    Reduced glutathione (GSH) is considered to exert a strong influence on cellular redox homeostasis and to regulate gene expression, but these processes remain poorly characterized. Severe GSH depletion specifically inhibited root meristem development, while low root GSH levels decreased lateral root densities. The redox potential of the nucleus and cytosol of Arabidopsis thaliana roots determined using roGFP probes was between -300 and -320 mV. Growth in the presence of the GSH-synthesis inhibitor buthionine sulfoximine (BSO) increased the nuclear and cytosolic redox potentials to approximately -260 mV. GSH-responsive genes including transcription factors (SPATULA, MYB15, MYB75), proteins involved in cell division, redox regulation (glutaredoxinS17, thioredoxins, ACHT5 and TH8) and auxin signalling (HECATE), were identified in the GSH-deficient root meristemless 1-1 (rml1-1) mutant, and in other GSH-synthesis mutants (rax1-1, cad2-1, pad2-1) as well as in the wild type following the addition of BSO. Inhibition of auxin transport had no effect on organ GSH levels, but exogenous auxin decreased the root GSH pool. We conclude that GSH depletion significantly increases the redox potentials of the nucleus and cytosol, and causes arrest of the cell cycle in roots but not shoots, with accompanying transcript changes linked to altered hormone responses, but not oxidative stress.

  11. Determination of the in vivo redox potential using roGFP and fluorescence spectra obtained from one-wavelength excitation

    NASA Astrophysics Data System (ADS)

    Wierer, S.; Elgass, K.; Bieker, S.; Zentgraf, U.; Meixner, A. J.; Schleifenbaum, F.

    2011-02-01

    The analysis of molecular processes in living (plant) cells such as signal transduction, DNA replication, carbon metabolism and senescence has been revolutionized by the use of green fluorescent protein (GFP) and its variants as specific cellular markers. Many cell biological processes are accompanied by changes in the intracellular redox potential. To monitor the redox potential, a redox-sensitive mutant of GFP (roGFP) was created, which shows changes in its optical properties in response to changes in the redox state of its surrounding medium. For a quantitative analysis in living systems, it is essential to know the optical properties of roGFP in vitro. Therefore, we applied spectrally resolved fluorescence spectroscopy on purified roGFP exposed to different redox potentials to determine shifts in both the absorption and the emission spectra of roGFP. Based on these in vitro findings, we introduce a new approach using one-wavelength excitation to use roGFP for the in vivo analysis of cell biological processes. We demonstrate the ability this technique by investigating chloroplast-located Grx1-roGFP2 expressing Arabidopsis thaliana cells as example for dynamically moving intracellular compartments. This is not possible with the two-wavelength excitation technique established so far, which hampers a quantitative analysis of highly mobile samples due to the time delay between the two measurements and the consequential displacement of the investigated area.

  12. Dietary Sulfur Amino Acid Effects on Fasting Plasma Cysteine/Cystine Redox Potential in Humans

    PubMed Central

    Jones, Dean P.; Park, Youngja; Gletsu-Miller, Nana; Liang, Yongliang; Yu, Tianwei; Accardi, Carolyn Jonas; Ziegler, Thomas R.

    2010-01-01

    Objective Oxidation of plasma cysteine/cystine (Cys/CySS) redox potential (EhCySS) has been associated with risk factors for cardiovascular disease in humans. Cys and CySS are derived from dietary sulfur amino acids (SAA), but the specific effects of SAA depletion and repletion on Cys/CySS redox indices are unknown. The present study examined the effect of dietary SAA intake level on free Cys, free CySS and EhCySS in human plasma under fasting conditions. Research Methods and Procedures Healthy individuals aged 18–36 y (n=13) were equilibrated to foods providing the RDA for SAA and then fed chemically defined diets without SAA (0 mg·kg−1·d−1; n=13) followed by SAA at levels approximating the mean (56 mg·kg−1·d−1; n=8) or 99th percentile (117 mg·kg−1·d−1; n=5) intake levels of Americans. Fasting plasma samples were collected daily during 4-d study periods and analyzed for free Cys, free CySS and the EhCySS. Results The SAA-free diet significantly (p<0.05) decreased plasma free Cys concentrations and oxidized EhCySS values after 4 days of SAA depletion. With SAA repletion at 56 mg·kg−1·d− 1, plasma free Cys increased significantly and values for EhCySS became more reducing. Administration of a diet providing a higher dose of SAA (117 mg·kg−1·d−1) resulted in a significantly higher level of free Cys and a more reducing EhCySS. Conclusions These results show that free Cys and Cys/CySS redox potential (EhCySS) in fasting plasma are affected by dietary SAA intake level in humans. Significant changes occur slowly over 4 days with insufficient SAA intake, but rapidly (after 1 day) with repletion. PMID:20471805

  13. Redox-responsive degradable PEG cryogels as potential cell scaffolds in tissue engineering.

    PubMed

    Dispinar, Tugba; Van Camp, Wim; De Cock, Liesbeth J; De Geest, Bruno G; Du Prez, Filip E

    2012-03-01

    A Michael addition strategy involving the reaction between a maleimide double bond and amine groups is investigated for the synthesis of cryogels at subzero temperature. Low-molecular-weight PEG-based building blocks with amine end groups and disulfide-containing building blocks with maleimide end groups are combined to synthesize redox-responsive PEG cryogels. The cryogels exhibit an interconnected macroporous morphology, a high compressive modulus and gelation yields of around 95%. While the cryogels are stable under physiological conditions, complete dissolution of the cryogels into water-soluble products is obtained in the presence of a reducing agent (glutathione) in the medium. Cell seeding experiments and toxicologic analysis demonstrate their potential as scaffolds in tissue engineering.

  14. Fluctuation Analysis of Redox Potential to Distinguish Microbial Fe(II) Oxidation

    NASA Astrophysics Data System (ADS)

    Enright, A. M. L.; Ferris, F. G.

    2016-11-01

    We developed a novel method for distinguishing abiotic and biological iron oxidation in liquid media using oxidation-reduction (redox) potential time series data. The instrument and processing algorithm were tested by immersing the tip of a Pt electrode with an Ag-AgCl reference electrode into an active iron-oxidizing biofilm in a groundwater discharge zone, as well as in two abiotic systems: a killed sample and a chemical control from the same site. We used detrended fluctuation analysis to characterize average root mean square fluctuation behavior, which was distinct in the live system. The calculated α value scaling exponents determined by detrended fluctuation analysis were significantly different at p < 0.001. This indicates that time series of electrode response data may be used to distinguish live and abiotic chemical reaction pathways. Due to the simplicity, portability, and small size, it may be suitable for characterization of extraterrestrial environments where water has been observed, such as Mars and Europa.

  15. Tunable redox potential of nonmetal doped monolayer MoS2: First principle calculations

    NASA Astrophysics Data System (ADS)

    Lu, S.; Li, C.; Zhao, Y. F.; Gong, Y. Y.; Niu, L. Y.; Liu, X. J.

    2016-10-01

    Doping is an effective method to alter the electronic behavior of materials by forming new chemical bonds and bringing bond relaxation. With this aid of first principle calculations, the crystal configuration and electronic properties of monolayer MoS2 have been modulated by the nonmetal (NM) dopants (H, B, C, N, O, F, Si, P, Cl, As, Se, Br, Te and I), and the thermodynamic stability depending on the preparation conditions (Mo-rich and S-rich conditions) were discussed. Results shown that, the NM dopants substituted preferentially for S under Mo-rich condition, the electronic distribution around the dopants and the nearby Mo atoms are changed by the new formed Mo-NM bonds and bands relaxation. Compared to pristine monolayer MoS2, the NM ions with odd chemical valences enhance the oxidation potential and reduce the reduction potential of specimens, but the NM ions with even chemical valences have the opposite effects on the redox potentials. Compared to the NM ions with even chemical valences, the lone pair electrons in NM ions with odd chemical valences can extra interact with the Mo ions and reduces the ECBM and EVBM values of specimens. It offers a simple way to design various monolayer MoS2 based catalysts in order to catalyze different materials by chose the reasonable dopants for stronger oxidation or reduction potential.

  16. Discharging a Li-S battery with ultra-high sulphur content cathode using a redox mediator

    PubMed Central

    Kim, Kwi Ryong; Lee, Kug-Seung; Ahn, Chi-Yeong; Yu, Seung-Ho; Sung, Yung-Eun

    2016-01-01

    Lithium-sulphur batteries are under intense research due to the high specific capacity and low cost. However, several problems limit their commercialization. One of them is the insulating nature of sulphur, which necessitates a large amount of conductive agent and binder in the cathode, reducing the effective sulphur load as well as the energy density. Here we introduce a redox mediator, cobaltocene, which acts as an electron transfer agent between the conductive surface and the polysulphides in the electrolyte. We confirmed that cobaltocene could effectively convert polysulphides to Li2S using scanning electron microscope, X-ray absorption near-edge structure and in-situ X-ray diffraction studies. This redox mediator enabled excellent electrochemical performance in a cathode with ultra-high sulphur content (80 wt%). It delivered 400 mAh g−1cathode capacity after 50 cycles, which is equivalent to 800 mAh g−1S in a typical cathode with 50 wt% sulphur. Furthermore, the volumetric capacity was also dramatically improved. PMID:27573528

  17. 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.

  18. Characterization of apoplast phenolics: Invitro oxidation of acetosyringone results in a rapid prolonged increase in the redox potential

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In a previous study we observed that if tobacco cell suspensions were inoculated with certain bacterial strains, several hours later the redox potential of the suspensions would increase (oxidative), as much as 100 mV, and in some cases last more than an hour. To discover possible contributors to t...

  19. Fluctuation Analysis of Redox Potential to Distinguish Microbial Fe(II) Oxidation.

    PubMed

    Enright, A M L; Ferris, F G

    2016-11-01

    We developed a novel method for distinguishing abiotic and biological iron oxidation in liquid media using oxidation-reduction (redox) potential time series data. The instrument and processing algorithm were tested by immersing the tip of a Pt electrode with an Ag-AgCl reference electrode into an active iron-oxidizing biofilm in a groundwater discharge zone, as well as in two abiotic systems: a killed sample and a chemical control from the same site. We used detrended fluctuation analysis to characterize average root mean square fluctuation behavior, which was distinct in the live system. The calculated α value scaling exponents determined by detrended fluctuation analysis were significantly different at p < 0.001. This indicates that time series of electrode response data may be used to distinguish live and abiotic chemical reaction pathways. Due to the simplicity, portability, and small size, it may be suitable for characterization of extraterrestrial environments where water has been observed, such as Mars and Europa. Key Words: Oxidation-reduction potential-Detrended fluctuation analysis-Iron-oxidizing bacteria. Astrobiology 16, 846-852.

  20. Electron acceptor redox potential globally regulates transcriptomic profiling in Shewanella decolorationis S12

    PubMed Central

    Lian, Yingli; Yang, Yonggang; Guo, Jun; Wang, Yan; Li, Xiaojing; Fang, Yun; Gan, Lixia; Xu, Meiying

    2016-01-01

    Electron acceptor redox potential (EARP) was presumed to be a determining factor for microbial metabolism in many natural and engineered processes. However, little is known about the potentially global effects of EARP on bacteria. In this study, we compared the physiological and transcriptomic properties of Shewanella decolorationis S12 respiring with different EARPs in microbial electrochemical systems to avoid the effects caused by the other physicochemical properties of real electron acceptor. Results showed that the metabolic activities of strain S12 were nonlinear responses to EARP. The tricarboxylic acid cycle for central carbon metabolism was down-regulated while glyoxylate shunt was up-regulated at 0.8 V compared to 0.2 and −0.2 V, which suggested that EARP is an important but not the only determinant for metabolic pathways of strain S12. Moreover, few cytochrome c genes were differentially expressed at different EARPs. The energy intensive flagella assembly and assimilatory sulfur metabolism pathways were significantly enriched at 0.8 V, which suggested strain S12 had stronger electrokinesis behavior and oxidative stress-response at high EARP. This study provides the first global information of EARP regulations on microbial metabolism, which will be helpful for understanding microorganism respiration. PMID:27503002

  1. Type 1 copper site synthetic model complexes with increased redox potentials.

    PubMed

    Yang, Lei; Tolman, William B

    2012-02-01

    Reactions of NaSCPh(3) with (R(3)tacn)Cu(OTf)(2) (R is Me, iPr; tacn is 1,4,7-triazacyclononane; OTf is CF(3)SO(3)(-)) yield blue complexes identified as ((R(3)tacn)CuSCPh(3))(OTf) on the basis of UV-vis, resonance Raman, and electron paramagnetic resonance (EPR) spectroscopy and electrospray ionization mass spectrometry. These complexes exhibit spectroscopic properties typical of type 1 copper sites in proteins, including diagnostic Sπ → Cu(d(x(2)-y(2))) ligand-to-metal charge transfer transitions at approximately 610-630 nm and small A(||) values in EPR spectra of less than 100 × 10(-4) cm(-1). Cyclic voltammetry experiments revealed redox potentials for the complexes similar to those of several low-potential type 1 copper proteins (e.g., azurin, stellacyanin) and approximately 0.5 V higher than those of previously reported model compounds. Thus, the new complexes mimic key aspects of both the structure and the function of type 1 copper sites.

  2. Electron acceptor redox potential globally regulates transcriptomic profiling in Shewanella decolorationis S12

    NASA Astrophysics Data System (ADS)

    Lian, Yingli; Yang, Yonggang; Guo, Jun; Wang, Yan; Li, Xiaojing; Fang, Yun; Gan, Lixia; Xu, Meiying

    2016-08-01

    Electron acceptor redox potential (EARP) was presumed to be a determining factor for microbial metabolism in many natural and engineered processes. However, little is known about the potentially global effects of EARP on bacteria. In this study, we compared the physiological and transcriptomic properties of Shewanella decolorationis S12 respiring with different EARPs in microbial electrochemical systems to avoid the effects caused by the other physicochemical properties of real electron acceptor. Results showed that the metabolic activities of strain S12 were nonlinear responses to EARP. The tricarboxylic acid cycle for central carbon metabolism was down-regulated while glyoxylate shunt was up-regulated at 0.8 V compared to 0.2 and ‑0.2 V, which suggested that EARP is an important but not the only determinant for metabolic pathways of strain S12. Moreover, few cytochrome c genes were differentially expressed at different EARPs. The energy intensive flagella assembly and assimilatory sulfur metabolism pathways were significantly enriched at 0.8 V, which suggested strain S12 had stronger electrokinesis behavior and oxidative stress-response at high EARP. This study provides the first global information of EARP regulations on microbial metabolism, which will be helpful for understanding microorganism respiration.

  3. Redox potentials and pKa for benzoquinone from density functional theory based molecular dynamics.

    PubMed

    Cheng, Jun; Sulpizi, Marialore; Sprik, Michiel

    2009-10-21

    The density functional theory based molecular dynamics (DFTMD) method for the computation of redox free energies presented in previous publications and the more recent modification for computation of acidity constants are reviewed. The method uses a half reaction scheme based on reversible insertion/removal of electrons and protons. The proton insertion is assisted by restraining potentials acting as chaperones. The procedure for relating the calculated deprotonation free energies to Brønsted acidities (pK(a)) and the oxidation free energies to electrode potentials with respect to the normal hydrogen electrode is discussed in some detail. The method is validated in an application to the reduction of aqueous 1,4-benzoquinone. The conversion of hydroquinone to quinone can take place via a number of alternative pathways consisting of combinations of acid dissociations, oxidations, or dehydrogenations. The free energy changes of all elementary steps (ten in total) are computed. The accuracy of the calculations is assessed by comparing the energies of different pathways for the same reaction (Hess's law) and by comparison to experiment. This two-sided test enables us to separate the errors related with the restrictions on length and time scales accessible to DFTMD from the errors introduced by the DFT approximation. It is found that the DFT approximation is the main source of error for oxidation free energies.

  4. Mechanism-Based Development of a Low-Potential, Soluble, and Cyclable Multielectron Anolyte for Nonaqueous Redox Flow Batteries.

    PubMed

    Sevov, Christo S; Fisher, Sydney L; Thompson, Levi T; Sanford, Melanie S

    2016-11-30

    The development of nonaqueous redox flow batteries (NRFBs) has been impeded by a lack of electroactive compounds (anolytes and catholytes) with the necessary combination of (1) redox potentials that exceed the potential limits of water, (2) high solubility in nonaqueous media, and (3) high stability toward electrochemical cycling. In addition, ideal materials would maintain all three of these properties over multiple electron transfer events, thereby providing a proportional increase in storage capacity. This paper describes the mechanism-based design of a new class of metal-coordination complexes (MCCs) as anolytes for NRFBs. The tridentate bipyridylimino isoindoline (BPI) ligands of these complexes were designed to enable multielectron redox events. These molecules were optimized using a combination of systematic variation of the BPI ligand and the metal center along with mechanistic investigations of the decomposition pathways that occur during electrochemical cycling. Ultimately, these studies led to the identification of nickel BPI complexes that could undergo stable charge-discharge cycling (<5% capacity loss over 200 cycles) as well as a derivative that possesses the previously unprecedented combination of high solubility (>700 mM in CH3CN), multiple electron transfers at low redox potentials (-1.7 and -1.9 V versus Ag/Ag(+)), and high stability in the charged state for days at high concentration. Overall, the studies described herein have enabled the identification of a promising anolyte candidate for NRFBs and have also provided key insights into chemical design principles for future classes of MCC-based anolytes.

  5. Evaluation of blood redox-balance, nitric oxide content and CCR6 rs3093024 in the genetic susceptibility during psoriasis.

    PubMed

    Matoshvili, M; Katsitadze, A; Sanikidze, T; Tophuria, D; D'Epiro, S; Richetta, A

    2015-03-01

    The aim of our study was to evaluate whether this polymorphism of CCR6 gene and oxidative stress are associated with psoriasis risk in Caucasian population. The association of the CCR6 polymorphism in the genetic susceptibility of psoriasis was performed at the Department of Dermatology and Venereology, Policlinico Umberto I of Rome (Italy). 516 participants were enrolled including 127 patients affected with psoriasis and 389 healthy controls. Cases and controls were genotyped, using a commercially available assay (Life Technologies, Carlsbad, California, USA) for CCR6 rs3093024 polymorphism. To verify the relations between genotypes and psoriasis risk we evaluated genotype frequencies for each individual DNA polymorphism in both case and control series. There were no differences in the genotype frequencies of the polymorphism between psoriasis cases and healthy controls. When patients with arthropathic psoriasis were excluded from the analysis, logistic regression showed that allele A was likely to reduce the risk of developing psoriasis in a dominant model. Logistic regression showed that male patients harboring the heterozygous genotype GA presented a reduced risk of developing psoriasis, compared with the reference GG genotype. None of the clinical features as age at onset, gender, family history of psoriasis, type of psoriasis, severity, BMI, smoking history or alcohol consumption, were associated with the genotype frequencies of the tested CCR6 polymorphism. In blood samples of patients with psoriasis intensive EPR signals of lipoperoxide (LOO.) free radicals were detected. Activity of blood SOD was significantly decreased in psoriatic patients compared to healthy controls. Activity of catalase was significantly increased in psoriatic patients, reflecting a high concentration of peroxide radicals. In blood samples of psoriatic patients decrease of free spin-trapped NO content were detected, that may be explained by biological transformation of NO into other

  6. Design of a single protein that spans the entire 2-V range of physiological redox potentials

    PubMed Central

    Hosseinzadeh, Parisa; Marshall, Nicholas M.; Yu, Yang; Nilges, Mark J.; New, Siu Yee; Tashkov, Stoyan A.; Blackburn, Ninian J.; Lu, Yi

    2016-01-01

    The reduction potential (E°′) is a critical parameter in determining the efficiency of most biological and chemical reactions. Biology employs three classes of metalloproteins to cover the majority of the 2-V range of physiological E°′s. An ultimate test of our understanding of E°′ is to find out the minimal number of proteins and their variants that can cover this entire range and the structural features responsible for the extreme E°′. We report herein the design of the protein azurin to cover a range from +970 mV to −954 mV vs. standard hydrogen electrode (SHE) by mutating only five residues and using two metal ions. Spectroscopic methods have revealed geometric parameters important for the high E°′. The knowledge gained and the resulting water-soluble redox agents with predictable E°′s, in the same scaffold with the same surface properties, will find wide applications in chemical, biochemical, biophysical, and biotechnological fields. PMID:26631748

  7. Spatio-temporal patterns of redox potential diffusive boundarys around Potamogeton crispus leaves and stems

    NASA Astrophysics Data System (ADS)

    Dong, B.

    2016-08-01

    To understand functions of a diffusive boundary layer around submerged macrophytes, the redox potential (ORP) around the leaves and stems of Potamogeton crispus were measured using a microsensor. Periphyton attached on macrophytes was analysed with the standard method. Results showed that significant spatio-temporal variations of ORP existed around leaves of P. crispus. In a vertical direction (within 2 mm), ORP significantly decreased with reducing distance from the leaf /stem surfaces and reached a minimum (428.51 mv) at the leaf /stem surface. The ORP microprofile was steepest around the mature leaf at the middle shoot and that of the senescent leaves at the basal shoot was relatively flat. At the temporal scale, the ORP microprofile was steepest at the stable growing stage, and those of the seedling stage and declining stage were relatively flat. Periphyton attached on P. crispus became dense gradually upon macrophyte entering growth stages. The results indicated that characteristics of ORP microprofiles were mainly affected by macrophytic physiological characteristics and periphyton synergistically.

  8. Redox potential driven aeration during very-high-gravity ethanol fermentation by using flocculating yeast

    PubMed Central

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

    2016-01-01

    Ethanol fermentation requires oxygen to maintain high biomass and cell viability, especially under very-high-gravity (VHG) condition. In this work, fermentation redox potential (ORP) was applied to drive the aeration process at low dissolved oxygen (DO) levels, which is infeasible to be regulated by a DO sensor. The performance and characteristics of flocculating yeast grown under 300 and 260 g glucose/L conditions were subjected to various aeration strategies including: no aeration; controlled aeration at −150, −100 and −50 mV levels; and constant aeration at 0.05 and 0.2 vvm. The results showed that anaerobic fermentation produced the least ethanol and had the highest residual glucose after 72 h of fermentation. Controlled aerations, depending on the real-time oxygen demand, led to higher cell viability than the no-aeration counterpart. Constant aeration triggered a quick biomass formation, and fast glucose utilization. However, over aeration at 0.2 vvm caused a reduction of final ethanol concentration. The controlled aeration driven by ORP under VHG conditions resulted in the best fermentation performance. Moreover, the controlled aeration could enhance yeast flocculating activity, promote an increase of flocs size, and accelerate yeast separation near the end of fermentation. PMID:27161047

  9. Redox potential tuning through differential quinone binding in the photosynthetic reaction center of Rhodobacter sphaeroides

    DOE PAGES

    Vermaas, Josh V.; Taguchi, Alexander T.; Dikanov, Sergei A.; ...

    2015-03-03

    Ubiquinone forms an integral part of the electron transport chain in cellular respiration and photosynthesis across a vast number of organisms. Prior experimental results have shown that the photosynthetic reaction center (RC) from Rhodobacter sphaeroides is only fully functional with a limited set of methoxy-bearing quinones, suggesting that specific interactions with this substituent are required to drive electron transport and the formation of quinol. The nature of these interactions has yet to be determined. Through parameterization of a CHARMM-compatible quinone force field and subsequent molecular dynamics simulations of the quinone-bound RC, in this paper we have investigated and characterized themore » interactions of the protein with the quinones in the QA and QB sites using both equilibrium simulation and thermodynamic integration. In particular, we identify a specific interaction between the 2-methoxy group of ubiquinone in the QB site and the amide nitrogen of GlyL225 that we implicate in locking the orientation of the 2-methoxy group, thereby tuning the redox potential difference between the quinones occupying the QA and QB sites. Finally, disruption of this interaction leads to weaker binding in a ubiquinone analogue that lacks a 2-methoxy group, a finding supported by reverse electron transfer electron paramagnetic resonance experiments of the QA–QB– biradical and competitive binding assays.« less

  10. Control of redox potential in hybridoma cultures: effects on MAb production, metabolism, and apoptosis.

    PubMed

    Meneses-Acosta, Angélica; Gómez, Alfonso; Ramírez, Octavio T

    2012-08-01

    Culture redox potential (CRP) has proven to be a valuable monitoring tool in several areas of biotechnology; however, it has been scarcely used in animal cell culture. In this work, a proportional feedback control was employed, for the first time, to maintain the CRP at different constant values in hybridoma batch cultures for production of a monoclonal antibody (MAb). Reducing and oxidant conditions, in the range of -130 and +70 mV, were maintained in 1-l bioreactors through automatic control of the inlet gas composition. Cultures at constant DOT, in the range of 3 and 300 %, were used for comparison. The effect of constant CRP on cell concentration, MAb production, metabolism of glucose, glutamine, thiols, oxygen consumption, and programmed cell death, was evaluated. Reducing conditions resulted in the highest viable cell and MAb concentrations and thiols production, whereas specific glucose and glutamine consumption rates remained at the lowest values. In such conditions, programmed cell death, particularly apoptosis, occurred only after nutrient exhaustion. The optimum specific MAb production rate occurred at intermediate CRP levels. Oxidant conditions resulted in a detrimental effect in all culture parameters, increasing the specific glucose, glutamine, and oxygen consumption rates and inducing the apoptotic process, which was detected as early as 24 h even when glutamine and glucose were present at non-limiting concentrations. In most cases, such results were similar to those obtained in control cultures at constant DOT.

  11. Influence of the heteroatom size on the redox potentials of selected polyoxoanions.

    PubMed

    Mbomekallé, Israël-Martyr; López, Xavier; Poblet, Josep M; Sécheresse, Francis; Keita, Bineta; Nadjo, Louis

    2010-08-02

    The apparent formal potentials for the one-electron redox process of most Keggin-type heteropolytungstates, XW(12)O(40)(q-), have long been shown to linearly depend on their overall negative charges, in the absence of proton interference in the process. However, for a given overall negative charge, these formal potentials are also shown here to depend on the specific central heteroatom X. In the present work, cyclic voltammetry was used to study a large variety of Keggin-type anions, under conditions where their comparisons are straightforward. In short, apparent potential values get more negative (the clusters are more difficult to reduce) for smaller central heteroatoms within a given family of Keggin-type heteropolyanions carrying the same overall negative charge. Density functional theory calculations were performed on the same family of Keggin compounds and satisfactorily reproduce these trends. They show that internal XO(4) units affect differently the tungstate oxide cage. The electrostatic potential created by each internal anionic unit in a fragment-like approach (XO(4)(q-)@W(12)O(36)) was analyzed, and it is observed that X atoms of the same group show slight differences. Within each group of the periodic table, X atoms with lower atomic numbers are also smaller in size. The net effect of such a tendency is to produce a more negative potential in the surroundings and thus a smaller capacity to accept electrons. The case of [BW(12)O(40)](5-) illustrates well this conclusion, with the smallest heteroatom of the Keggin series with group III central elements and a very negative reduction potential with respect to the other elements of the same group. Particularly in this case, the electronic structure of the Keggin anion shows the effects of the small size of boron: the highest occupied molecular orbitals of [BW(12)O(40)](5-) appear to be approximately 0.35 eV higher than those in the other clusters of the same charge, explaining that the BO(4) unit is more

  12. Control of a redox reaction on lipid bilayer surfaces by membrane dipole potential.

    PubMed Central

    Alakoskela, J I; Kinnunen, P K

    2001-01-01

    Nitro-2,1,3-benzoxadiazol-4-yl (NBD) group is a widely used, environment-sensitive fluorescent probe. The negatively charged dithionite rapidly reduces the accessible NBD-labeled lipids in liposomes to their corresponding nonfluorescent derivatives. In this study both the phospholipid headgroup and acyl chain NBD-labeled L-alpha-1,2-dipalmitoyl-sn-glycero-3-phospho-[N-(4-nitrobenz-2-oxa-1,3-diazole)-ethanolamine] (DPPN) and 1-acyl-2-[12-[(7-nitro-2,1,3-benzoxadiazol-4-yl)amino]dodecanoyl]-sn-glycero-3-phosphocholine (NBD-PC), respectively, were employed. The correlation of both the rate coefficient k(1) of the redox reaction and the fluorescence properties of the two probes with the membrane dipole potential Psi in fluid dipalmitoylglycerophosphocholine (DPPC) liposomes is demonstrated. When Psi of the bilayer was varied (decreased by phloretin or increased by 6-ketocholestanol), the value for k1 decreased for both DPPN and NBD-PC with increasing Psi. For both fluorophores a positive correlation to Psi was evident for the relative fluorescence emission intensity (RFI, normalized to the emission of the fluorophore in a DPPC matrix). The relative changes in emission intensity as a function of Psi were approximately equal for both NBD derivatives. Changes similar to those caused by phloretin were seen when dihexadecylglycerophosphocholine (DHPC) was added to DPPC liposomes, in keeping with the lower dipole potential for the former lipid compound compared with DPPC. These effects of Psi on NBD fluorescence should be taken into account when interpreting data acquired using NBD-labeled lipids as fluorescent probes. PMID:11159402

  13. Control of a redox reaction on lipid bilayer surfaces by membrane dipole potential.

    PubMed

    Alakoskela, J I; Kinnunen, P K

    2001-01-01

    Nitro-2,1,3-benzoxadiazol-4-yl (NBD) group is a widely used, environment-sensitive fluorescent probe. The negatively charged dithionite rapidly reduces the accessible NBD-labeled lipids in liposomes to their corresponding nonfluorescent derivatives. In this study both the phospholipid headgroup and acyl chain NBD-labeled L-alpha-1,2-dipalmitoyl-sn-glycero-3-phospho-[N-(4-nitrobenz-2-oxa-1,3-diazole)-ethanolamine] (DPPN) and 1-acyl-2-[12-[(7-nitro-2,1,3-benzoxadiazol-4-yl)amino]dodecanoyl]-sn-glycero-3-phosphocholine (NBD-PC), respectively, were employed. The correlation of both the rate coefficient k(1) of the redox reaction and the fluorescence properties of the two probes with the membrane dipole potential Psi in fluid dipalmitoylglycerophosphocholine (DPPC) liposomes is demonstrated. When Psi of the bilayer was varied (decreased by phloretin or increased by 6-ketocholestanol), the value for k1 decreased for both DPPN and NBD-PC with increasing Psi. For both fluorophores a positive correlation to Psi was evident for the relative fluorescence emission intensity (RFI, normalized to the emission of the fluorophore in a DPPC matrix). The relative changes in emission intensity as a function of Psi were approximately equal for both NBD derivatives. Changes similar to those caused by phloretin were seen when dihexadecylglycerophosphocholine (DHPC) was added to DPPC liposomes, in keeping with the lower dipole potential for the former lipid compound compared with DPPC. These effects of Psi on NBD fluorescence should be taken into account when interpreting data acquired using NBD-labeled lipids as fluorescent probes.

  14. Brassinosteroid Ameliorates Zinc Oxide Nanoparticles-Induced Oxidative Stress by Improving Antioxidant Potential and Redox Homeostasis in Tomato Seedling

    PubMed Central

    Li, Mengqi; Ahammed, Golam J.; Li, Caixia; Bao, Xiao; Yu, Jingquan; Huang, Chunlei; Yin, Hanqin; Zhou, Jie

    2016-01-01

    In the last few decades use of metal-based nanoparticles (MNPs) has been increased significantly that eventually contaminating agricultural land and limiting crop production worldwide. Moreover, contamination of food chain with MNPs has appeared as a matter of public concern due to risk of potential health hazard. Brassinosteroid has been shown to play a critical role in alleviating heavy metal stress; however, its function in relieving zinc oxide nanoparticles (ZnO NPs)-induced phytotoxicity remains unknown. In this study, we investigated the potential role of 24-epibrassinolide (BR) in mitigating ZnO NPs-induced toxicity in tomato seedlings. Seedling growth, biomass production, and root activity gradually decreased, but Zn accumulation increased with increasing ZnO NPs concentration (10–100 mg/L) in growth media (½ MS). The augmentation of BR (5 nM) in media significantly ameliorated 50 mg/L ZnO NPs-induced growth inhibition. Visualization of hydrogen peroxide (H2O2), and quantification of H2O2 and malondialdehyde (MDA) in tomato roots confirmed that ZnO NPs induced an oxidative stress. However, combined treatment with BR and ZnO NPs remarkably reduced concentration of H2O2 and MDA as compared with ZnO NPs only treatment, indicating that BR supplementation substantially reduced oxidative stress. Furthermore, the activities of key antioxidant enzymes such as superoxide dismutase (SOD), catalase, ascorbate peroxidase and glutathione reductase were increased by combined treatment of BR and ZnO NPs compared with ZnO NPs only treatment. BR also increased reduced glutathione (GSH), but decreased oxidized glutathione (GSSG)] and thus improved cellular redox homeostasis by increasing GSH:GSSG ratio. The changes in relative transcript abundance of corresponding antioxidant genes such as Cu/Zn SOD, CAT1, GSH1, and GR1 were in accordance with the changes in those antioxidants under different treatments. More importantly, combined application of BR and ZnO NPs

  15. Differentiation between stoichiometric and anticatalytic antioxidant properties of benzoic acid analogues: a structure/redox potential relationship study.

    PubMed

    Franck, Thierry; Mouithys-Mickalad, Ange; Robert, Thierry; Ghitti, Gianangelo; Deby-Dupont, Ginette; Neven, Philippe; Serteyn, Didier

    2013-11-25

    We investigated the antioxidant activities of some phenolic acid derivatives on a cell free system and on cellular and enzymatic models involved in inflammation. The stoichiometric antioxidant activities of phenolic acid derivatives were studied by measuring their capacity to scavenge the radical cation 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS(+)) and reactive oxygen species (ROS) produced by stimulated neutrophils. The anticatalytic antioxidant capacity of the molecules was evaluated on the activity of myeloperoxidase (MPO), an oxidant enzyme present in and released by the primary granules of neutrophils. The ROS produced by PMA-stimulated neutrophils were measured by lucigenin-enhanced chemiluminescence (CL) and the potential interaction of the molecules with MPO was investigated without interferences due to medium by Specific Immuno-Extraction Followed by Enzyme Detection (SIEFED). The antioxidant activities of the phenolic compounds were correlated to their redox potentials measured by differential pulse voltammetry (DPV), and discussed in relation to their molecular structure. The ability of the phenolic molecules to scavenge ABTS radicals and ROS derived from neutrophils was inversely correlated to their increased redox potential. The number of hydroxyl groups (three) and their position (catechol) were essential for their efficacy as stoichiometric antioxidants or scavengers. On MPO activity, the inhibitory capacity of the molecules was not really correlated with their redox potential. Likewise, for the inhibition of MPO activity the number of OH groups and mainly the elongation of the carboxylic group were essential, probably by facilitating the interaction with the active site or the structure of the enzyme. The redox potential measurement, combined with ABTS and CL techniques, seems to be a good technique to select stoichiometric antioxidants but not anticatalytic ones, as seen for MPO, what rather involves a direct interaction with

  16. Biological redox cycling of iron in nontronite and its potential application in nitrate removal.

    PubMed

    Zhao, Linduo; Dong, Hailiang; Kukkadapu, Ravi K; Zeng, Qiang; Edelmann, Richard E; Pentrák, Martin; Agrawal, Abinash

    2015-05-05

    Biological redox cycling of structural Fe in phyllosilicates is an important but poorly understood process. The objective of this research was to study microbially mediated redox cycles of Fe in nontronite (NAu-2). During the reduction phase, structural Fe(III) in NAu-2 served as electron acceptor, lactate as electron donor, AQDS as electron shuttle, and dissimilatory Fe(III)-reducing bacterium Shewanella putrefaciens CN32 as mediator in bicarbonate- and PIPES-buffered media. During the oxidation phase, biogenic Fe(II) served as electron donor and nitrate as electron acceptor. Nitrate-dependent Fe(II)-oxidizing bacterium Pseudogulbenkiania sp. strain 2002 was added as mediator in the same media. For all three cycles, structural Fe in NAu-2 was able to reversibly undergo three redox cycles without significant dissolution. Fe(II) in bioreduced samples occurred in two distinct environments, at edges and in the interior of the NAu-2 structure. Nitrate reduction to nitrogen gas was coupled with oxidation of edge-Fe(II) and part of interior-Fe(II) under both buffer conditions, and its extent and rate did not change with Fe redox cycles. These results suggest that biological redox cycling of structural Fe in phyllosilicates is a reversible process and has important implications for biogeochemical cycles of carbon, nitrogen, and other nutrients in natural environments.

  17. Improving the oxidative stability of a high redox potential fungal peroxidase by rational design.

    PubMed

    Sáez-Jiménez, Verónica; Acebes, Sandra; Guallar, Victor; Martínez, Angel T; Ruiz-Dueñas, Francisco J

    2015-01-01

    Ligninolytic peroxidases are enzymes of biotechnological interest due to their ability to oxidize high redox potential aromatic compounds, including the recalcitrant lignin polymer. However, different obstacles prevent their use in industrial and environmental applications, including low stability towards their natural oxidizing-substrate H2O2. In this work, versatile peroxidase was taken as a model ligninolytic peroxidase, its oxidative inactivation by H2O2 was studied and different strategies were evaluated with the aim of improving H2O2 stability. Oxidation of the methionine residues was produced during enzyme inactivation by H2O2 excess. Substitution of these residues, located near the heme cofactor and the catalytic tryptophan, rendered a variant with a 7.8-fold decreased oxidative inactivation rate. A second strategy consisted in mutating two residues (Thr45 and Ile103) near the catalytic distal histidine with the aim of modifying the reactivity of the enzyme with H2O2. The T45A/I103T variant showed a 2.9-fold slower reaction rate with H2O2 and 2.8-fold enhanced oxidative stability. Finally, both strategies were combined in the T45A/I103T/M152F/M262F/M265L variant, whose stability in the presence of H2O2 was improved 11.7-fold. This variant showed an increased half-life, over 30 min compared with 3.4 min of the native enzyme, under an excess of 2000 equivalents of H2O2. Interestingly, the stability improvement achieved was related with slower formation, subsequent stabilization and slower bleaching of the enzyme Compound III, a peroxidase intermediate that is not part of the catalytic cycle and leads to the inactivation of the enzyme.

  18. Leaching of Zinc Sulfide by Thiobacillus ferrooxidans: Experiments with a Controlled Redox Potential Indicate No Direct Bacterial Mechanism

    PubMed Central

    Fowler, T. A.; Crundwell, F. K.

    1998-01-01

    The role of Thiobacillus ferrooxidans in bacterial leaching of mineral sulfides is controversial. Much of the controversy is due to the fact that the solution conditions, especially the concentrations of ferric and ferrous ions, change during experiments. The role of the bacteria would be more easily discernible if the concentrations of ferric and ferrous ions were maintained at set values throughout the experimental period. In this paper we report results obtained by using the constant redox potential apparatus described previously (P. I. Harvey and F. K. Crundwell, Appl. Environ. Microbiol. 63:2586–2592, 1997). This apparatus is designed to control the redox potential in the leaching compartment of an electrolytic cell by reduction or oxidation of dissolved iron. By controlling the redox potential the apparatus maintains the concentrations of ferrous and ferric ions at their initial values. Experiments were conducted in the presence of T. ferrooxidans and under sterile conditions. Analysis of the conversion of zinc sulfide in the absence of the bacteria and analysis of the conversion of zinc sulfate in the presence of the bacteria produced the same results. This indicates that the only role of the bacteria under the conditions used is regeneration of ferric ions in solution. In this work we found no evidence that there is a direct mechanism for bacterial leaching. PMID:9758769

  19. Electron Pathways through Erythrocyte Plasma Membrane in Human Physiology and Pathology: Potential Redox Biomarker?

    PubMed

    Matteucci, Elena; Giampietro, Ottavio

    2007-09-17

    Erythrocytes are involved in the transport of oxygen and carbon dioxide in the body. Since pH is the influential factor in the Bohr-Haldane effect, pHi is actively maintained via secondary active transports Na(+)/H(+) exchange and HC(3) (-)/Cl(-) anion exchanger. Because of the redox properties of the iron, hemoglobin generates reactive oxygen species and thus, the human erythrocyte is constantly exposed to oxidative damage. Although the adult erythrocyte lacks protein synthesis and cannot restore damaged proteins, it is equipped with high activity of protective enzymes. Redox changes in the cell initiate various signalling pathways. Plasma membrane oxido-reductases (PMORs) are transmembrane electron transport systems that have been found in the membranes of all cells and have been extensively characterized in the human erythrocyte. Erythrocyte PMORs transfer reducing equivalents from intracellular reductants to extracellular oxidants, thus their most important role seems to be to enable the cell respond to changes in intra- and extra-cellular redox environments.So far the activity of erythrocyte PMORs in disease states has not been systematically investigated. This review summarizes present knowledge on erythrocyte electron transfer activity in humans (health, type 1 diabetes, diabetic nephropathy, and chronic uremia) and hypothesizes an integrated model of the functional organization of erythrocyte plasma membrane where electron pathways work in parallel with transport metabolons to maintain redox homeostasis.

  20. AN EVALUATION OF ELECTRODE INSERTION TECHNIQUES FOR MEASUREMENT OF REDOX POTENTIAL IN ESTUARINE SEDIMENTS

    EPA Science Inventory

    Eh measurements by electrodes are commonly used to characterize redox status of sediments in freshwater, marine and estuarine studies, due to the relative ease and rapidity of data collection. In our studies of fine-grained estuarine seabeds, we observed that Eh values measured i...

  1. ELECTRODE MEASUREMENT OF REDOX POTENTIAL IN ANAEROBIC FERRIC/FERROUS CHLORIDE SYSTEMS

    EPA Science Inventory

    The behaviour of two inert redox electrodes (Pt and wax-impregnated graphite) was investigated in anaerobic ferrous and ferric chloride solutions in order to establish if these electrodes respond to the Fe3+/Fe2+ couple in a Nernstian manner. A new method fo...

  2. Redox Disrupting Potential of ToxCast™Chemicals Ranked by Activity in Mouse Embryonic Stem Cells

    EPA Science Inventory

    Little is known regarding the adverse outcome pathways responsible for developmental toxicity following exposure to chemicals. An evaluation of Toxoast™ Phase I chemicals in an adherent mouse embryonic stem cell (mESC) assay revealed a redox sensitive pathway that correlated with...

  3. REDOX DISRUPTING POTENTIAL OF TOXCAST CHEMICALS RANKED BY ACTIVITY IN MOUSE EMBRYONIC STEM CELLS

    EPA Science Inventory

    To gain insight regarding the adverse outcome pathways leading to developmental toxicity following exposure to chemicals, we evaluated ToxCast™ Phase I chemicals in an adherent mouse embryonic stem cell (mESC) assay and identified a redox sensitive pathway that correlated with al...

  4. Effect of the L499M mutation of the ascomycetous Botrytis aclada laccase on redox potential and catalytic properties

    SciTech Connect

    Osipov, Evgeny; Kittl, Roman; Shleev, Sergey; Dorovatovsky, Pavel; Tikhonova, Tamara; Popov, Vladimir

    2014-11-01

    The structures of the ascomycetous B. aclada laccase and its L499M T1-site mutant have been solved at 1.7 Å resolution. The mutant enzyme shows a 140 mV lower redox potential of the type 1 copper and altered kinetic behaviour. The wild type and the mutant have very similar structures, which makes it possible to relate the changes in the redox potential to the L499M mutation Laccases are members of a large family of multicopper oxidases that catalyze the oxidation of a wide range of organic and inorganic substrates accompanied by the reduction of dioxygen to water. These enzymes contain four Cu atoms per molecule organized into three sites: T1, T2 and T3. In all laccases, the T1 copper ion is coordinated by two histidines and one cysteine in the equatorial plane and is covered by the side chains of hydrophobic residues in the axial positions. The redox potential of the T1 copper ion influences the enzymatic reaction and is determined by the nature of the axial ligands and the structure of the second coordination sphere. In this work, the laccase from the ascomycete Botrytis aclada was studied, which contains conserved Ile491 and nonconserved Leu499 residues in the axial positions. The three-dimensional structures of the wild-type enzyme and the L499M mutant were determined by X-ray crystallography at 1.7 Å resolution. Crystals suitable for X-ray analysis could only be grown after deglycosylation. Both structures did not contain the T2 copper ion. The catalytic properties of the enzyme were characterized and the redox potentials of both enzyme forms were determined: E{sub 0} = 720 and 580 mV for the wild-type enzyme and the mutant, respectively. Since the structures of the wild-type and mutant forms are very similar, the change in the redox potential can be related to the L499M mutation in the T1 site of the enzyme.

  5. Relationship between redox potentials, the inhibition of mitochondrial respiration and the production of toxic oxygen species by flavonoids

    SciTech Connect

    Hodnick, W.F.; Milosavljevic, E.B.; Nelson, J.H.; Pardini, R.S.

    1986-05-01

    Flavonoids have been shown to inhibit mitochondrial respiration and produce oxy-radicals. They have also been shown to possess diverse biological activities, some of which have been speculated to be dependent upon their redox activity. The authors have investigated the redox behavior of a series of structurally related flavonoids employing cyclic voltammetry under physiological conditions. The flavonoids that autoxidized and produced oxygen radicals had reduction potentials (E 1/2) significantly lower (-30 to +60 mV) than those that didn't autoxidize (+130 to +340 mV). The E 1/2 values for the autoxidizable flavonoids compare to the E 1/2 range of -70 to +30 mv (le/sup -/ reduction potential) for optimum quinone induced production of superoxide (O/sub 2//sup -/) in mitochondrial NADH-CoQ reductase (complex I). The authors reported that the most potent flavonoid inhibitors of mitochondrial succinate-CoQ reductase (complex II) possessed hydroxyl configurations capable of supporting redox reactions. For a series of 3,5,7-trihydroxyflavones which differed by b-ring hydroxylation it was found that decreasing E 1/2 of the flavonoids was associated with decreasing I/sub 50/ values towards succinoxidase. These findings suggest that the electrochemical properties of the flavonoids may contribute to their biological activity.

  6. In vivo ROS and redox potential fluorescent detection in plants: Present approaches and future perspectives.

    PubMed

    Ortega-Villasante, Cristina; Burén, Stefan; Barón-Sola, Ángel; Martínez, Flor; Hernández, Luis E

    2016-10-15

    Reactive oxygen species (ROS) are metabolic by-products in aerobic organisms including plants. Endogenously produced ROS act as cellular messengers and redox regulators involved in several plant biological processes, but excessive accumulation of ROS cause oxidative stress and cell damage. Understanding ROS signalling and stress responses requires precise imaging and quantification of local, subcellular and global ROS dynamics with high selectivity, sensitivity, and spatiotemporal resolution. Several fluorescent vital dyes have been tested so far, which helped to provide relevant spatially resolved information of oxidative stress dynamics in plants subjected to harmful environmental conditions. However, certain plant characteristics, such as high background fluorescence of plant tissues in vivo and antioxidant mechanisms, can interfere with ROS detection. The development of improved small-molecule fluorescent dyes and protein-based ROS sensors targeted to subcellular compartments will enable in vivo monitoring of ROS and redox changes in photosynthetic organisms.

  7. Electron-transfer studies with a new flavin adenine dinucleotide dependent glucose dehydrogenase and osmium polymers of different redox potentials.

    PubMed

    Zafar, Muhammad Nadeem; Wang, Xiaoju; Sygmund, Christoph; Ludwig, Roland; Leech, Dónal; Gorton, Lo

    2012-01-03

    A new extracellular flavin adenine dinucleotide (FAD)-dependent glucose dehydrogenase from Glomerella cingulata (GcGDH) was electrochemically studied as a recognition element in glucose biosensors. The redox enzyme was recombinantly produced in Pichia pastoris and homogeneously purified, and its glucose-oxidizing properties on spectrographic graphite electrodes were investigated. Six different Os polymers, the redox potentials of which ranged in a broad potential window between +15 and +489 mV versus the normal hydrogen electrode (NHE), were used to immobilize and "wire" GcGDH to the spectrographic graphite electrode's surface. The GcGDH/Os polymer modified electrodes were evaluated by chronoamperometry using flow injection analysis. The current response was investigated using a stepwisely increased applied potential. It was observed that the ratio of GcGDH/Os polymer and the overall loading of the enzyme electrode significantly affect the performance of the enzyme electrode for glucose oxidation. The best-suited Os polymer [Os(4,4'-dimethyl-2,2'-bipyridine)(2)(PVI)Cl](+) had a potential of +309 mV versus NHE, and the optimum GcGDH/Os polymer ratio was 1:2 yielding a maximum current density of 493 μA·cm(-2) at a 30 mM glucose concentration.

  8. Effect of the L499M mutation of the ascomycetous Botrytis aclada laccase on redox potential and catalytic properties

    PubMed Central

    Osipov, Evgeny; Polyakov, Konstantin; Kittl, Roman; Shleev, Sergey; Dorovatovsky, Pavel; Tikhonova, Tamara; Hann, Stephan; Ludwig, Roland; Popov, Vladimir

    2014-01-01

    Laccases are members of a large family of multicopper oxidases that catalyze the oxidation of a wide range of organic and inorganic substrates accompanied by the reduction of dioxygen to water. These enzymes contain four Cu atoms per molecule organized into three sites: T1, T2 and T3. In all laccases, the T1 copper ion is coordinated by two histidines and one cysteine in the equatorial plane and is covered by the side chains of hydrophobic residues in the axial positions. The redox potential of the T1 copper ion influences the enzymatic reaction and is determined by the nature of the axial ligands and the structure of the second coordination sphere. In this work, the laccase from the ascomycete Botrytis aclada was studied, which contains conserved Ile491 and nonconserved Leu499 residues in the axial positions. The three-dimensional structures of the wild-type enzyme and the L499M mutant were determined by X-ray crystallography at 1.7 Å resolution. Crystals suitable for X-ray analysis could only be grown after deglycosylation. Both structures did not contain the T2 copper ion. The catalytic properties of the enzyme were characterized and the redox potentials of both enzyme forms were determined: E 0 = 720 and 580 mV for the wild-type enzyme and the mutant, respectively. Since the structures of the wild-type and mutant forms are very similar, the change in the redox potential can be related to the L499M mutation in the T1 site of the enzyme. PMID:25372682

  9. Mathematical modelling of the combined effect of water activity, pH and redox potential on the heat destruction.

    PubMed

    Reichart, O; Mohácsi-Farkas, C

    1994-12-01

    Heat destruction of seven foodborne microorganisms (Lactobacillus plantarum, Lactobacillus brevis, Saccharomyces cerevisiae, Zygosaccharomyces bailii, Yarrowia lipolytica, Paecilomyces varioti and Neosartoria fischeri) as a function of the temperature, pH, redox potential and water activity was studied in synthetic heating media. Several mathematical models were developed for describing the heat destruction rate, most of them resulted in a good correlation between the fitted and measured values. The determination coefficients of the model-fitting were the best in case of lactobacilli and moulds (0.96-0.99) and the worst in case of the yeasts (0.81-0.88).

  10. Rhizome phyllosphere oxygenation in Phragmites and other species in relation to redox potential, convective gas flow, submergence and aeration pathways.

    PubMed

    Armstrong, J; Jones, R E; Armstrong, W

    2006-01-01

    Underground rhizomes of emergent aquatic macrophytes are important for perennation, vegetative spread, competition and anchorage. In four species we examined the potential for the development of oxidized phyllospheres around rhizome apical buds, similar to the protective oxygenated rhizospheres around roots. Redox potentials and polarographic measurements of radial oxygen loss were recorded using platinum cathodes around the apical buds. The aeration pathway from atmosphere to phyllosphere was investigated anatomically and by applied pressurized gas flow. Redox potentials increased by +400, +45, +200 and +340 mV around rhizome apices of Phragmites australis, Oryza rhizomatis, Carex rostrata and Glyceria maxima, respectively. Radial oxygen loss from rhizome apices of Phragmites was increased by convective gas flow through the rhizome and by shoot de-submergence, and decreased by resistances applied within the aeration pathway and by shoot submergence. We conclude that oxygen passes via internal gas-space connections between aerial shoot, rhizome and underground buds and into the phyllosphere regions via scale-leaf stomata and surfaces on the buds. We suggest that oxidized phyllospheres may protect rhizome apices against phytotoxins in waterlogged soils, just as oxidized rhizospheres protect roots.

  11. Injectable redox-polymerized methylcellulose hydrogels as potential soft tissue filler materials.

    PubMed

    Gold, Gittel T; Varma, Devika M; Harbottle, David; Gupta, Michelle S; Stalling, Simone S; Taub, Peter J; Nicoll, Steven B

    2014-12-01

    There is a significant clinical need for long-lasting, injectable materials for soft tissue reconstruction. Methylcellulose (MC) is an FDA-approved polysaccharide derivative of cellulose that is inexpensive, renewable, and biocompatible, and may serve as an alternative to existing synthetic and natural fillers. In this study, MC was modified with functional methacrylate groups and polymerized using a redox-initiation system to produce hydrogels with tunable properties. By varying the percent methacrylation and macromer concentration, the equilibrium moduli of the hydrogels were found to range between 1.29 ± 0.46 and 12.8 ± 2.94 kPa, on par with human adipose tissue, and also displayed an inverse relationship to the swelling properties. Rheological analyses determined gelation onset and completion to be in accordance with the ISO standard for injectable materials. Cellulase enzymatic treatment resulted in complete degradation of the hydrogels by 48 h, presenting the possibility of minimally invasive removal of the materials in the event of malposition or host reaction. In addition, co-culture experiments with human dermal fibroblasts showed the gels to be cytocompatible based on DNA measurements and Live/Dead staining. Taken together, these redox-polymerized MC hydrogels may be of use for a wide range of clinical indications requiring soft tissue augmentation.

  12. An Assessment of Potential Efficiency Gains through Online Content Use

    ERIC Educational Resources Information Center

    Creaser, Claire; Hamblin, Yvonne; Davies, J. Eric

    2006-01-01

    Purpose: Online content has largely replaced traditional print-based resources as the primary tool for literature searching throughout much of the academic and research community. This paper presents the results of a small-scale study, commissioned by the JISC in 2004, to assess the potential efficiency gains that may be achieved through the use…

  13. 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.

  14. Importance of Hydrogen Bonding in Fine Tuning the [2Fe-2S] Cluster Redox Potential of HydC from Thermotoga maritima.

    PubMed

    Birrell, James A; Laurich, Christoph; Reijerse, Edward J; Ogata, Hideaki; Lubitz, Wolfgang

    2016-08-09

    Iron-sulfur clusters form one of the largest and most diverse classes of enzyme cofactors in nature. They may serve as structural factors, form electron transfer chains between active sites and external redox partners, or form components of enzyme active sites. Their specific role is a consequence of the cluster type and the surrounding protein environment. The relative effects of these factors are not completely understood, and it is not yet possible to predict the properties of iron-sulfur clusters based on amino acid sequences or rationally tune their properties to generate proteins with new desirable functions. Here, we generate mutations in a [2Fe-2S] cluster protein, the TmHydC subunit of the trimeric [FeFe]-hydrogenase from Thermotoga maritima, to study the factors that affect its redox potential. Saturation mutagenesis of Val131 was used to tune the redox potential over a 135 mV range and revealed that cluster redox potential and electronic properties correlate with amino acid hydrophobicity and the ability to form hydrogen bonds to the cluster. Proline scanning mutagenesis between pairs of ligating cysteines was used to remove backbone amide hydrogen bonds to the cluster and decrease the redox potential by up to 132 mV, without large structural changes in most cases. However, substitution of Gly83 with proline caused a change of HydC to a [4Fe-4S] cluster protein with a redox potential of -526 mV. Together, these results confirm the importance of hydrogen bonding in tuning cluster redox potentials and demonstrate the versatility of iron-sulfur cluster protein folds at binding different types of clusters.

  15. Transcriptome analysis of Lactococcus lactis subsp. lactis during milk acidification as affected by dissolved oxygen and the redox potential.

    PubMed

    Larsen, Nadja; Moslehi-Jenabian, Saloomeh; Werner, Birgit Brøsted; Jensen, Maiken Lund; Garrigues, Christel; Vogensen, Finn Kvist; Jespersen, Lene

    2016-06-02

    Performance of Lactococcus lactis as a starter culture in dairy fermentations depends on the levels of dissolved oxygen and the redox state of milk. In this study the microarray analysis was used to investigate the global gene expression of L. lactis subsp. lactis DSM20481(T) during milk acidification as affected by oxygen depletion and the decrease of redox potential. Fermentations were carried out at different initial levels of dissolved oxygen (dO2) obtained by milk sparging with oxygen (high dO2, 63%) or nitrogen (low dO2, 6%). Bacterial exposure to high initial oxygen resulted in overexpression of genes involved in detoxification of reactive oxygen species (ROS), oxidation-reduction processes, biosynthesis of trehalose and down-regulation of genes involved in purine nucleotide biosynthesis, indicating that several factors, among them trehalose and GTP, were implicated in bacterial adaptation to oxidative stress. Generally, transcriptional changes were more pronounced during fermentation of oxygen sparged milk. Genes up-regulated in response to oxygen depletion were implicated in biosynthesis and transport of pyrimidine nucleotides, branched chain amino acids and in arginine catabolic pathways; whereas genes involved in salvage of nucleotides and cysteine pathways were repressed. Expression pattern of genes involved in pyruvate metabolism indicated shifts towards mixed acid fermentation after oxygen depletion with production of specific end-products, depending on milk treatment. Differential expression of genes, involved in amino acid and pyruvate pathways, suggested that initial oxygen might influence the release of flavor compounds and, thereby, flavor development in dairy fermentations. The knowledge of molecular responses involved in adaptation of L. lactis to the shifts of redox state and pH during milk fermentations is important for the dairy industry to ensure better control of cheese production.

  16. Effects of Moisture Content and Redox Potential on in situ Kd Values for Radiodine in Soil

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Understanding the processes that determine the solid-liquid partitioning (Kd value) of Se are of fundamental importance in assessing the risk associated with the disposal of radioselenium-containing waste. Using a mini-column approach, in-situ Kd values for 75Se were determined over time in relation...

  17. Polarization curve measurements combined with potential probe sensing for determining current density distribution in vanadium redox-flow batteries

    NASA Astrophysics Data System (ADS)

    Becker, Maik; Bredemeyer, Niels; Tenhumberg, Nils; Turek, Thomas

    2016-03-01

    Potential probes are applied to vanadium redox-flow batteries for determination of effective felt resistance and current density distribution. During the measurement of polarization curves in 100 cm2 cells with different carbon felt compression rates, alternating potential steps at cell voltages between 0.6 V and 2.0 V are applied. Polarization curves are recorded at different flow rates and states of charge of the battery. Increasing compression rates lead to lower effective felt resistances and a more uniform resistance distribution. Low flow rates at high or low state of charge result in non-linear current density distribution with high gradients, while high flow rates give rise to a nearly linear behavior.

  18. Electron Flow in Multiheme Bacterial Cytochromes is a Balancing Act Between Heme Electronic Interaction and Redox Potentials

    SciTech Connect

    Breuer, Marian; Rosso, Kevin M.; Blumberger, Jochen

    2014-01-14

    The naturally widespread process of electron transfer from metal reducing bacteria to extracellular solid metal oxides entails unique biomolecular machinery optimized for long-range electron transport. To perform this function efficiently microorganisms have adapted multi-heme c-type cytochromes to arrange heme cofactors into wires that cooperatively span the cellular envelope, transmitting electrons along distances greater than 100 Angstroms. Implications and opportunities for bionanotechnological device design are self-evident. However, at the molecular level how these proteins shuttle electrons along their heme wires, navigating intraprotein intersections and interprotein interfaces effciently, remains a mystery so far inaccessible to experiment. To shed light on this critical topic, we carried out extensive computer simulations to calculate Marcus theory quantities for electron transfer along the ten heme cofactors in the recently crystallized outer membrane cytochrome MtrF. The combination of electronic coupling matrix elements with free energy calculations of heme redox potentials and reorganization energies for heme-to-heme electron transfer allows the step-wise and overall electron transfer rate to be estimated and understood in terms of structural and dynamical characteristics of the protein. By solving a master equation for electron hopping, we estimate an intrinsic, maximum possible electron flux through solvated MtrF of 104-105 s-1, consistent with recently measured rates for the related MtrCAB protein complex. Intriguingly, this flux must navigate thermodynamically uphill steps past low potential hemes. Our calculations show that the rapid electron transport through MtrF is the result of a clear correlation between heme redox potential and the strength of electronic coupling along the wire: Thermodynamically uphill steps occur only between electronically well connected stacked heme pairs. This suggests that the protein evolved to harbor low potential

  19. Humin as an electron donor for enhancement of multiple microbial reduction reactions with different redox potentials in a consortium.

    PubMed

    Zhang, Dongdong; Zhang, Chunfang; Xiao, Zhixing; Suzuki, Daisuke; Katayama, Arata

    2015-02-01

    A solid-phase humin, acting as an electron donor, was able to enhance multiple reductive biotransformations, including dechlorination of pentachlorophenol (PCP), dissimilatory reduction of amorphous Fe (III) oxide (FeOOH), and reduction of nitrate, in a consortium. Humin that was chemically reduced by NaBH4 served as an electron donor for these microbial reducing reactions, with electron donating capacities of 0.013 mmol e(-)/g for PCP dechlorination, 0.15 mmol e(-)/g for iron reduction, and 0.30 mmol e(-)/g for nitrate reduction. Two pairs of oxidation and reduction peaks within the humin were detected by cyclic voltammetry analysis. 16S rRNA gene sequencing-based microbial community analysis of the consortium incubated with different terminal electron acceptors, suggested that Dehalobacter sp., Bacteroides sp., and Sulfurospirillum sp. were involved in the PCP dechlorination, dissimilatory iron reduction, and nitrate reduction, respectively. These findings suggested that humin functioned as a versatile redox mediator, donating electrons for multiple respiration reactions with different redox potentials.

  20. 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.

  1. Milk acidification by Lactococcus lactis is improved by decreasing the level of dissolved oxygen rather than decreasing redox potential in the milk prior to inoculation.

    PubMed

    Jeanson, Sophie; Hilgert, Nadine; Coquillard, Marie-Odile; Seukpanya, Céline; Faiveley, Marc; Neveu, Pascal; Abraham, Christophe; Georgescu, Véra; Fourcassié, Pascal; Beuvier, Eric

    2009-04-30

    Although redox potential is very rarely taken into account in food fermentation it could be as influential as pH on bacterial activities. Lactococcus lactis is already known to exhibit a powerful reducing activity in milk but its reduction activity was shown to occur prior to its acidification activity with a potential interaction between these two lactococcal activities. Therefore, acidification lag-type phase could be shortened by decreasing the redox potential of milk before inoculation. As the redox potential is highly dependent on the dissolved oxygen level, our objective was to study their separate and combined influences on acidification and growth kinetics of pure L. lactis strains in milk. Results showed that high level of dissolved oxygen is significantly more influential on growth, and even more on acidification kinetics, than initial decreased redox potential of milk. Reduction of milk was drastic and mostly due to bacterial activity. The redox potential of milk only dropped when dissolved oxygen was entirely consumed. When there was no dissolved oxygen from the beginning, L. lactis immediately decreased the redox potential of milk and acidified afterwards. When the level of dissolved oxygen was initially high, acidification and reduction of milk occurred at the same time. Acidification kinetics was then biphasic with a slower rate during the aerobic stage and a faster rate during the anaerobic stage. The seven strains tested demonstrated diversity in both their acidification kinetics and their adaptation to high level of dissolved oxygen, independent of their growth kinetics. To conclude, we have shown that the level of dissolved oxygen in milk has a dramatic influence on acidification kinetics and could be used to control acidification kinetics in dairy industries.

  2. Electrochemistry of the [4Fe4S] Cluster in Base Excision Repair Proteins: Tuning the Redox Potential with DNA.

    PubMed

    Bartels, Phillip L; Zhou, Andy; Arnold, Anna R; Nuñez, Nicole N; Crespilho, Frank N; David, Sheila S; Barton, Jacqueline K

    2017-03-02

    Escherichia coli endonuclease III (EndoIII) and MutY are DNA glycosylases that contain [4Fe4S] clusters and that serve to maintain the integrity of the genome after oxidative stress. Electrochemical studies on highly oriented pyrolytic graphite (HOPG) revealed that DNA binding by EndoIII leads to a large negative shift in the midpoint potential of the cluster, consistent with stabilization of the oxidized [4Fe4S](3+) form. However, the smooth, hydrophobic HOPG surface is nonideal for working with proteins in the absence of DNA. In this work, we use thin film voltammetry on a pyrolytic graphite edge electrode to overcome these limitations. Improved adsorption leads to substantial signals for both EndoIII and MutY in the absence of DNA, and a large negative potential shift is retained with DNA present. In contrast, the EndoIII mutants E200K, Y205H, and K208E, which provide electrostatic perturbations in the vicinity of the cluster, all show DNA-free potentials within error of wild type; similarly, the presence of negatively charged poly-l-glutamate does not lead to a significant potential shift. Overall, binding to the DNA polyanion is the dominant effect in tuning the redox potential of the [4Fe4S] cluster, helping to explain why all DNA-binding proteins with [4Fe4S] clusters studied to date have similar DNA-bound potentials.

  3. Redox Modulating NRF2: A Potential Mediator of Cancer Stem Cell Resistance

    PubMed Central

    Ryoo, In-geun; Lee, Sang-hwan; Kwak, Mi-Kyoung

    2016-01-01

    Tumors contain a distinct small subpopulation of cells that possess stem cell-like characteristics. These cells have been called cancer stem cells (CSCs) and are thought to be responsible for anticancer drug resistance and tumor relapse after therapy. Emerging evidence indicates that CSCs share many properties, such as self-renewal and quiescence, with normal stem cells. In particular, CSCs and normal stem cells retain low levels of reactive oxygen species (ROS), which can contribute to stem cell maintenance and resistance to stressful tumor environments. Current literatures demonstrate that the activation of ataxia telangiectasia mutated (ATM) and forkhead box O3 (FoxO3) is associated with the maintenance of low ROS levels in normal stem cells such as hematopoietic stem cells. However, the importance of ROS signaling in CSC biology remains poorly understood. Recent studies demonstrate that nuclear factor-erythroid 2-related factor 2 (NRF2), a master regulator of the cellular antioxidant defense system, is involved in the maintenance of quiescence, survival, and stress resistance of CSCs. Here, we review the recent findings on the roles of NRF2 in maintenance of the redox state and multidrug resistance in CSCs, focusing on how NRF2-mediated ROS modulation influences the growth and resistance of CSCs. PMID:26682001

  4. NoxE NADH Oxidase and the Electron Transport Chain Are Responsible for the Ability of Lactococcus lactis To Decrease the Redox Potential of Milk▿ †

    PubMed Central

    Tachon, Sybille; Brandsma, Johannes Bernhard; Yvon, Mireille

    2010-01-01

    The redox potential plays a major role in the microbial and sensorial quality of fermented dairy products. The redox potential of milk (around 400 mV) is mainly due to the presence of oxygen and many other oxidizing compounds. Lactococcus lactis has a strong ability to decrease the redox potential of milk to a negative value (−220 mV), but the molecular mechanisms of milk reduction have never been addressed. In this study, we investigated the impact of inactivation of genes encoding NADH oxidases (noxE and ahpF) and components of the electron transport chain (ETC) (menC and noxAB) on the ability of L. lactis to decrease the redox potential of ultrahigh-temperature (UHT) skim milk during growth under aerobic and anaerobic conditions. Our results revealed that elimination of oxygen is required for milk reduction and that NoxE is mainly responsible for the rapid removal of oxygen from milk before the exponential growth phase. The ETC also contributes slightly to oxygen consumption, especially during the stationary growth phase. We also demonstrated that the ETC is responsible for the decrease in the milk redox potential from 300 mV to −220 mV when the oxygen concentration reaches zero or under anaerobic conditions. This suggests that the ETC is responsible for the reduction of oxidizing compounds other than oxygen. Moreover, we found great diversity in the reducing activities of natural L. lactis strains originating from the dairy environment. This diversity allows selection of specific strains that can be used to modulate the redox potential of fermented dairy products to optimize their microbial and sensorial qualities. PMID:20038695

  5. Influence of DOM and redox potential on the leaching of As and Cr from coal fly ash

    NASA Astrophysics Data System (ADS)

    Deonarine, A.; Kolker, A.; Huggins, F.; Foster, A. L.

    2012-12-01

    Coal ash, a byproduct of coal-fired power plants, contains toxic trace elements such as arsenic (As) and chromium (Cr). Coal ash has recently been scrutinized as a potential source of toxic trace elements to aquatic systems and potable water sources, and the legislation pertinent to coal ash management is currently under revision. Coal ash is currently stored in surface impoundments and landfills that are poorly regulated and at risk of failure. Impoundment failure can result in the mobilization of coal ash and leachates into aquatic systems and potable water-sources. The current understanding of the environmental fate (i.e., transformation, toxicity and mobility) of As and Cr in coal ash is largely limited to leaching protocols that are not environmentally relevant, as they exclude parameters such as redox potential and dissolved organic matter (DOM) that are prevalent in aquatic systems. Furthermore, the relationship between coal-ash particle size and the speciation and leaching behavior of As and Cr has not been well investigated. The size of host particles may influence the speciation and coordination environment of trace elements, and may be a critical factor in the leaching/dissolution behavior of As and Cr from coal ash into solution. In this study, coal ash samples from three different coal-fired power plants using different coal sources and different combustion processes were segregated into size fractions (< 1 mm to ≥ 100 μm, < 100 μm to ≥ 10 μm, < 10 μm to ≥ 1 μm, and < 1 μm) using a combination of dry sieving and particle impaction. Coal ash size fractions were examined using synchrotron x-ray absorption spectroscopy (XANES/ EXAFS) to determine whether there were any differences in As and Cr concentration and speciation/coordination environment as a function of particle size. Coal-ash size fractions were also exposed to a buffered solution (pH ~7) with varying DOM concentration (1 to 30 mg/L) and redox potential (reducing, oxic). Dissolved

  6. The effect of hydrazine dosing on high temperature pH{sub T} and redox potentials under PWR environments

    SciTech Connect

    Maekelae, K.; Aaltonen, P.; Buddas, T.

    1995-10-01

    The release and deposit of corrosion products, which play a key role in activity transport, are controlled by the properties of the primary water and oxides present on component surfaces. Some of the VVER 440 type reactors have started to use hydrazine dosing to primary coolant instead of ammonia, because it has been shown to be efficient in reducing activity transport. On the other hand, some other studies have shown that there is no significant difference between new VVER units using hydrazine dosing and the ones operating with standard potassium/ammonia water chemistry. In this paper the results are presented concerning the out-of-core high temperature water chemistry and incore redox potential measurements at Rez research reactor in Czech Republic during hydrazine/ammonia water chemistries.

  7. Hole scavenger redox potentials determine quantum efficiency and stability of Pt-decorated CdS nanorods for photocatalytic hydrogen generation

    NASA Astrophysics Data System (ADS)

    Berr, Maximilian J.; Wagner, Peter; Fischbach, Stefan; Vaneski, Aleksandar; Schneider, Julian; Susha, Andrei S.; Rogach, Andrey L.; Jäckel, Frank; Feldmann, Jochen

    2012-05-01

    We use Pt-decorated CdS nanorods for photocatalytic hydrogen generation in the presence of sacrificial hole scavengers. Both the quantum efficiency for hydrogen generation and the stability of the colloidal nanocrystals in solution improve with increasing redox potential of the hole scavenger. The higher redox potential leads to faster hole scavenging, which increases quantum efficiency and stability since electron hole recombination and oxidation of the CdS become less important. The quantum efficiencies can be tuned over more than an order of magnitude. This finding is important for choosing hole scavengers and for comparing efficiencies and stabilities for different photocatalytic nanosystems.

  8. Hole scavenger redox potentials determine quantum efficiency and stability of Pt-decorated CdS nanorods for photocatalytic hydrogen generation

    SciTech Connect

    Berr, Maximilian J.; Wagner, Peter; Fischbach, Stefan; Schneider, Julian; Jaeckel, Frank; Feldmann, Jochen; Vaneski, Aleksandar; Susha, Andrei S.; Rogach, Andrey L.

    2012-05-28

    We use Pt-decorated CdS nanorods for photocatalytic hydrogen generation in the presence of sacrificial hole scavengers. Both the quantum efficiency for hydrogen generation and the stability of the colloidal nanocrystals in solution improve with increasing redox potential of the hole scavenger. The higher redox potential leads to faster hole scavenging, which increases quantum efficiency and stability since electron hole recombination and oxidation of the CdS become less important. The quantum efficiencies can be tuned over more than an order of magnitude. This finding is important for choosing hole scavengers and for comparing efficiencies and stabilities for different photocatalytic nanosystems.

  9. Effects of dynamic redox zonation on the potential for natural attenuation of trichloroethylene at a fire-training-impacted aquifer

    USGS Publications Warehouse

    Skubal, K.L.; Haack, S.K.; Forney, L.J.; Adriaens, P.

    1999-01-01

    Hydrogeochemical and microbiological methods were used to characterize temporal changes along a transect of an aquifer contaminated by mixed hydrocarbon and solvent wastes from fire training activities at Wurtsmith Air Force Base (Oscoda, MI). Predominant terminal electron accepting processes (TEAPs) as measured by dissolved hydrogen indicated reoxygenation along the transect between October 1995 and October 1996, possibly because of recharge, fluctuations in water table elevation, or microbial activity. Microbiological analyses using universal and archaeal probes revealed a relationship between groundwater hydrogen concentration, TEAP, and predominant bacterial phylogeny. Specifically, a raised water table level and evidence of methanogenesis corresponded to an order of magnitude increase in archaeal 16S rRNA relative to when this zone was unsaturated. Spatial microbial and geochemical dynamics did not result in measurable differences in trichloroethylene (TCE) mineralization potential in vadose, capillary fringe, and saturated zone soils during a 500-day microcosm experiment using unprocessed contaminated soil and groundwater. Aerobic systems indicated that methane, but not toluene, may serve as cosubstrate for TCE cometabolism. Anaerobic microcosms demonstrated evidence for methanogenesis, CO2 production and hydrogen consumption, yet dechlorination activity was only observed in a microcosm with sulfate-reduction as the dominant TEAP. Mass balance calculations indicated less than 5% mineralization, regardless of redox zone or degree of saturation, at maximum rates of 0.01-0.03 ??mol/g soil??d. The general lack of dechlorination activity under laboratory conditions corroborates the limited evidence for natural dechlorination at this site, despite abundant electron donor material and accumulated organic acids from microbial degradation of alkylbenzenes. Thus, the short-term temporal dynamics in redox conditions is unlikely to have measurable effects on the long

  10. Uranium isotopes as a potential global-ocean redox proxy: a test from the Upper Pennsylvanian Hushpuckney Shale (Kansas, U.S.A.)

    NASA Astrophysics Data System (ADS)

    Herrmann, A. D.; Algeo, T. J.; Gordon, G. W.; Anbar, A. D.

    2015-12-01

    Uranium (U) isotope variation in marine sediments has been proposed as a proxy for changes in average global-ocean redox conditions. Here, we investigate U isotope variation in the black shale (BS) member of the Hushpuckney Shale (Swope Formation) at two sites ~400 km apart within the Late Paleozoic Midcontinent Sea (LPMS) of North America, with the goal of testing whether sediment δ238U records a global-ocean redox signal or local environmental influences. Our results document a spatial gradient of at least 0.25‰ in δ238U within the LPMS, demonstrating that local (probably redox) controls have overprinted any global U-isotope signal. Furthermore, the pattern of stratigraphic variation in δ238U in both study cores, with low values (‒0.4 to ‒0.2‰) at the base and top and peak values (+0.4 to +0.65‰) in the middle of the BS, is inconsistent with dominance of a global-ocean redox signal because (1) the middle of the BS was deposited at maximum eustatic highstand when euxinic conditions existed most widely within the LPMS and coeval epicontinental seas, and (2) more extensive euxinia should have shifted global-ocean seawater δ238U to lower values based on mass-balance principles. On the other hand, the observed δ238U pattern is consistent with a dominant local redox control, with larger U-isotope fractionations associated with more reducing bottom waters. We therefore conclude that U was not removed quantitatively to euxinic facies of the LPMS, and that sediment U-isotope compositions were controlled mainly by local redox and hydrographic factors. Our results imply that U-isotope signals from epicontinental-sea sections must be vetted carefully through analysis of high-resolution datasets at multiple sites in order to validate their potential use as a global-seawater redox proxy.

  11. Electrochemistry of cations in diopsidic melt - Determining diffusion rates and redox potentials from voltammetric curves

    NASA Technical Reports Server (NTRS)

    Colson, Russell O.; Haskin, Larry A.; Crane, Daniel

    1990-01-01

    Results are presented on determinations of reduction potentials and their temperature dependence of selected ions in diopsidic melt, by using linear sweep voltammetry. Diffusion coefficients were measured for cations of Eu, Mn, Cr, and In. Enthalpies and entropies of reduction were determined for the cations V(V), Cr(3+), Mn(2+), Mn(3+), Fe(2+), Cu(2+), Mo(VI), Sn(IV), and Eu(3+). Reduction potentials were used to study the structural state of cations in the melt.

  12. Density functional theory calculations of the redox potentials of actinide(VI)/actinide(V) couple in water.

    PubMed

    Steele, Helen M; Guillaumont, Dominique; Moisy, Philippe

    2013-05-30

    The measured redox potential of an actinide at an electrode surface involves the transfer of a single electron from the electrode surface on to the actinide center. Before electron transfer takes place, the complexing ligands and molecules of solvation need to become structurally arranged such that the electron transfer is at its most favorable. Following the electron transfer, there is further rearrangement to obtain the minimum energy structure for the reduced state. As such, there are three parts to the total energy cycle required to take the complex from its ground state oxidized form to its ground state reduced form. The first part of the energy comes from the structural rearrangement and solvation energies of the actinide species before the electron transfer or charge transfer process; the second part, the energy of the electron transfer; the third part, the energy required to reorganize the ligands and molecules of solvation around the reduced species. The time resolution of electrochemical techniques such as cyclic voltammetry is inadequate to determine to what extent bond and solvation rearrangement occurs before or after electron transfer; only for a couple to be classed as reversible is it fast in terms of the experimental time. Consequently, the partitioning of the energy theoretically is of importance to obtain good experimental agreement. Here we investigate the magnitude of the instantaneous charge transfer through calculating the fast one electron reduction energies of AnO2(H2O)n(2+), where An = U, Np, and Pu, for n = 4-6, in solution without inclusion of the structural optimization energy of the reduced form. These calculations have been performed using a number of DFT functionals, including the recently developed functionals of Zhao and Truhlar. The results obtained for calculated electron affinities in the aqueous phase for the AnO2(H2O)5(2+/+) couples are within 0.04 V of accepted experimental redox potentials, nearly an order of magnitude

  13. 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

  14. O2, pH, and redox potential microprofiles around Potamogeton malaianus measured using microsensors.

    PubMed

    Dong, Bin; Han, Ruiming; Wang, Guoxiang; Cao, Xun

    2014-01-01

    This study aimed to elucidate the effects of periphyton on the microprofiles of oxygen (O2), pH, and oxidation-reduction potential around the stems and leaves of a submerged macrophyte Potamogeton malaianus and on the plant growth in the eutrophic shallow Taihu Lake, China. The microprofiles were measured using a motorized microprofiling system equipped with microsensors. The leaf age of the macrophyte and periphyton exerted significant effects on the microprofiles of O2, pH, and oxidation-reduction potential. O2 concentration and pH increased whereas the oxidation-reduction potential decreased with decreasing distance to the stem/leaf surface. The fluctuation amplitudes of O2, pH, and oxidation-reduction potential were the largest in the microprofiles of mature leaves and the lowest in senescent leaves. The periphyton increased the thickness of the broad diffusive boundary layer and fluctuation amplitudes of O2, pH, and oxidation-reduction potential. When the periphyton was removed, the thickness of the broad diffusive boundary layer in the microprofiles of stems, senescent leaves, and mature leaves reduced by 29.0%, 49.72%, and 70.34%, and the O2, pH, and oxidation-reduction potential fluctuation amplitudes also declined accordingly. Our results suggest that a thick periphyton exerted negative effects on the growth of macrophytes by providing extensive shading and creating a barrier that hindered the transport of dissolved substances such as O2, and led to premature decline in macrophytes in the eutrophic Taihu Lake. The consequent implications can help to elucidate the control mechanism of the broad diffusive boundary layer around macrophytes on nutrient cycling in eutrophic waters and to better understand the role of this layer in the Taihu Lake and other similar eutrophic waters.

  15. Microbial redox processes in deep subsurface environments and the potential application of (per)chlorate in oil reservoirs.

    PubMed

    Liebensteiner, Martin G; Tsesmetzis, Nicolas; Stams, Alfons J M; Lomans, Bartholomeus P

    2014-01-01

    The ability of microorganisms to thrive under oxygen-free conditions in subsurface environments relies on the enzymatic reduction of oxidized elements, such as sulfate, ferric iron, or CO2, coupled to the oxidation of inorganic or organic compounds. A broad phylogenetic and functional diversity of microorganisms from subsurface environments has been described using isolation-based and advanced molecular ecological techniques. The physiological groups reviewed here comprise iron-, manganese-, and nitrate-reducing microorganisms. In the context of recent findings also the potential of chlorate and perchlorate [jointly termed (per)chlorate] reduction in oil reservoirs will be discussed. Special attention is given to elevated temperatures that are predominant in the deep subsurface. Microbial reduction of (per)chlorate is a thermodynamically favorable redox process, also at high temperature. However, knowledge about (per)chlorate reduction at elevated temperatures is still scarce and restricted to members of the Firmicutes and the archaeon Archaeoglobus fulgidus. By analyzing the diversity and phylogenetic distribution of functional genes in (meta)genome databases and combining this knowledge with extrapolations to earlier-made physiological observations we speculate on the potential of (per)chlorate reduction in the subsurface and more precisely oil fields. In addition, the application of (per)chlorate for bioremediation, souring control, and microbial enhanced oil recovery are addressed.

  16. Microbial redox processes in deep subsurface environments and the potential application of (per)chlorate in oil reservoirs

    PubMed Central

    Liebensteiner, Martin G.; Tsesmetzis, Nicolas; Stams, Alfons J. M.; Lomans, Bartholomeus P.

    2014-01-01

    The ability of microorganisms to thrive under oxygen-free conditions in subsurface environments relies on the enzymatic reduction of oxidized elements, such as sulfate, ferric iron, or CO2, coupled to the oxidation of inorganic or organic compounds. A broad phylogenetic and functional diversity of microorganisms from subsurface environments has been described using isolation-based and advanced molecular ecological techniques. The physiological groups reviewed here comprise iron-, manganese-, and nitrate-reducing microorganisms. In the context of recent findings also the potential of chlorate and perchlorate [jointly termed (per)chlorate] reduction in oil reservoirs will be discussed. Special attention is given to elevated temperatures that are predominant in the deep subsurface. Microbial reduction of (per)chlorate is a thermodynamically favorable redox process, also at high temperature. However, knowledge about (per)chlorate reduction at elevated temperatures is still scarce and restricted to members of the Firmicutes and the archaeon Archaeoglobus fulgidus. By analyzing the diversity and phylogenetic distribution of functional genes in (meta)genome databases and combining this knowledge with extrapolations to earlier-made physiological observations we speculate on the potential of (per)chlorate reduction in the subsurface and more precisely oil fields. In addition, the application of (per)chlorate for bioremediation, souring control, and microbial enhanced oil recovery are addressed. PMID:25225493

  17. The Effect of Complex Formation upon the Redox Potentials of Metallic Ions. Cyclic Voltammetry Experiments.

    ERIC Educational Resources Information Center

    Ibanez, Jorge G.; And Others

    1988-01-01

    Describes experiments in which students prepare in situ soluble complexes of metal ions with different ligands and observe and estimate the change in formal potential that the ion undergoes upon complexation. Discusses student formation and analysis of soluble complexes of two different metal ions with the same ligand. (CW)

  18. Complexation Effect on Redox Potential of Iron(III)-Iron(II) Couple: A Simple Potentiometric Experiment

    ERIC Educational Resources Information Center

    Rizvi, Masood Ahmad; Syed, Raashid Maqsood; Khan, Badruddin

    2011-01-01

    A titration curve with multiple inflection points results when a mixture of two or more reducing agents with sufficiently different reduction potentials are titrated. In this experiment iron(II) complexes are combined into a mixture of reducing agents and are oxidized to the corresponding iron(III) complexes. As all of the complexes involve the…

  19. CRISPR Content Correlates with the Pathogenic Potential of Escherichia coli.

    PubMed

    García-Gutiérrez, Enriqueta; Almendros, Cristóbal; Mojica, Francisco J M; Guzmán, Noemí M; García-Martínez, Jesús

    2015-01-01

    Guide RNA molecules (crRNA) produced from clustered regularly interspaced short palindromic repeat (CRISPR) arrays, altogether with effector proteins (Cas) encoded by cognate cas (CRISPR associated) genes, mount an interference mechanism (CRISPR-Cas) that limits acquisition of foreign DNA in Bacteria and Archaea. The specificity of this action is provided by the repeat intervening spacer carried in the crRNA, which upon hybridization with complementary sequences enables their degradation by a Cas endonuclease. Moreover, CRISPR arrays are dynamic landscapes that may gain new spacers from infecting elements or lose them for example during genome replication. Thus, the spacer content of a strain determines the diversity of sequences that can be targeted by the corresponding CRISPR-Cas system reflecting its functionality. Most Escherichia coli strains possess either type I-E or I-F CRISPR-Cas systems. To evaluate their impact on the pathogenicity of the species, we inferred the pathotype and pathogenic potential of 126 strains of this and other closely related species and analyzed their repeat content. Our results revealed a negative correlation between the number of I-E CRISPR units in this system and the presence of pathogenicity traits: the median number of repeats was 2.5-fold higher for commensal isolates (with 29.5 units, range 0-53) than for pathogenic ones (12.0, range 0-42). Moreover, the higher the number of virulence factors within a strain, the lower the repeat content. Additionally, pathogenic strains of distinct ecological niches (i.e., intestinal or extraintestinal) differ in repeat counts. Altogether, these findings support an evolutionary connection between CRISPR and pathogenicity in E. coli.

  20. Quantum Mechanics/Molecular Mechanics Method Combined with Hybrid All-Atom and Coarse-Grained Model: Theory and Application on Redox Potential Calculations.

    PubMed

    Shen, Lin; Yang, Weitao

    2016-04-12

    We developed a new multiresolution method that spans three levels of resolution with quantum mechanical, atomistic molecular mechanical, and coarse-grained models. The resolution-adapted all-atom and coarse-grained water model, in which an all-atom structural description of the entire system is maintained during the simulations, is combined with the ab initio quantum mechanics and molecular mechanics method. We apply this model to calculate the redox potentials of the aqueous ruthenium and iron complexes by using the fractional number of electrons approach and thermodynamic integration simulations. The redox potentials are recovered in excellent accordance with the experimental data. The speed-up of the hybrid all-atom and coarse-grained water model renders it computationally more attractive. The accuracy depends on the hybrid all-atom and coarse-grained water model used in the combined quantum mechanical and molecular mechanical method. We have used another multiresolution model, in which an atomic-level layer of water molecules around redox center is solvated in supramolecular coarse-grained waters for the redox potential calculations. Compared with the experimental data, this alternative multilayer model leads to less accurate results when used with the coarse-grained polarizable MARTINI water or big multipole water model for the coarse-grained layer.

  1. Surface packing determines the redox potential shift of cytochrome c adsorbed on gold.

    PubMed

    Zanetti-Polzi, Laura; Daidone, Isabella; Bortolotti, Carlo Augusto; Corni, Stefano

    2014-09-17

    Thermodynamic and dynamic properties of iso-1-cytochrome c covalently bound to a bare gold surface are here investigated by large scale atomistic simulations. The reduction potential of the protein for low and high surface concentrations is calculated showing a good agreement with experimental estimates. The origin of the dependence of the reduction potential on the surface concentration is investigated and is demonstrated to stem from the changing polarizability of the environment surrounding the protein, a mechanism reminiscent of crowding effects. Moreover, structural analyses are performed revealing relevant changes induced by the presence of the electrode on the dynamic properties of cytochrome c. In particular, one of the two cavities previously identified on the protein surface [Bortolotti et al. J. Am. Chem. Soc., 2012, 134, 13670], and that reversibly open in cytochrome c freely diffusing in solution, is found to be deformed when the protein is adsorbed on gold. This modification exemplifies a mechanism that potentially leads to changes in the protein properties by surface-induced modification of its dynamical behavior.

  2. A new direction in dye-sensitized solar cells redox mediator development: in situ fine-tuning of the cobalt(II)/(III) redox potential through Lewis base interactions.

    PubMed

    Kashif, Muhammad K; Axelson, Jordan C; Duffy, Noel W; Forsyth, Craig M; Chang, Christopher J; Long, Jeffrey R; Spiccia, Leone; Bach, Udo

    2012-10-10

    Dye-sensitized solar cells (DSCs) are an attractive renewable energy technology currently under intense investigation. In recent years, one area of major interest has been the exploration of alternatives to the classical iodide/triiodide redox shuttle, with particular attention focused on cobalt complexes with the general formula [Co(L)(n)](2+/3+). We introduce a new approach to designing redox mediators that involves the application of [Co(PY5Me(2))(MeCN)](2+/3+) complexes, where PY5Me(2) is the pentadentate ligand, 2,6-bis(1,1-bis(2-pyridyl)ethyl)pyridine. It is shown, by X-ray crystallography, that the axial acetonitrile (MeCN) ligand can be replaced by more strongly coordinating Lewis bases (B) to give complexes with the general formula [Co(PY5Me(2))(B)](2+/3+), where B = 4-tert-butylpyridine (tBP) or N-methylbenzimidazole (NMBI). These commonly applied DSC electrolyte components are used for the first time to fine-tune the potential of the redox couple to the requirements of the dye through coordinative interactions with the Co(II/III) centers. Application of electrolytes based on the [Co(PY5Me(2))(NMBI)](2+/3+) complex in combination with a commercially available organic sensitizer has enabled us to attain DSC efficiencies of 8.4% and 9.2% at a simulated light intensity of 100% sun (1000 W m(-2) AM1.5 G) and at 10% sun, respectively, higher than analogous devices applying the [Co(bpy)(3)](2+/3+) redox couple, and an open circuit voltage (V(oc)) of almost 1.0 V at 100% sun for devices constructed with the tBP complex.

  3. Effect of dissolved oxygen on redox potential and milk acidification by lactic acid bacteria isolated from a DL-starter culture.

    PubMed

    Larsen, Nadja; Werner, Birgit Brøsted; Vogensen, Finn Kvist; Jespersen, Lene

    2015-03-01

    Milk acidification by DL-starter cultures [cultures containing Lactococcus lactis diacetylactis (D) and Leuconostoc (L) species] depends on the oxidation-reduction (redox) potential in milk; however, the mechanisms behind this effect are not completely clear. The objective of this study was to investigate the effect of dissolved oxygen on acidification kinetics and redox potential during milk fermentation by lactic acid bacteria (LAB). Fermentations were conducted by single strains isolated from mixed DL-starter culture, including Lactococcus lactis ssp. lactis, Lactococcus lactis ssp. cremoris, and Leuconostoc mesenteroides ssp. cremoris, by the DL-starter culture, and by the type strains. High and low levels of oxygen were produced by flushing milk with oxygen or nitrogen, respectively. The kinetics of milk acidification was characterized by the maximum rate and time of acidification (Vamax and Tamax), the maximum rate and time of reduction (Vrmax and Trmax), the minimum redox potential (Eh7 final), and time of reaching Eh7 final (Trfinal). Variations in kinetic parameters were observed at both the species and strain levels. Two of the Lc. lactis ssp. lactis strains were not able to lower redox potential to negative values. Kinetic parameters of the DL-starter culture were comparable with the best acidifying and reducing strains, indicating their additive effects. Acidification curves were mostly diauxic at all oxygen levels, displaying 2 maxima of acidification rate: before (aerobic maximum) and after (anaerobic maximum) oxygen depletion. The redox potential decreased concurrently with oxygen consumption and continued to decrease at slower rate until reaching the final values, indicating involvement of both oxygen and microbiological activity in the redox state of milk. Oxygen flushing had a negative effect on reduction and acidification capacity of tested LAB. Reduction was significantly delayed at high initial oxygen, exhibiting longer Trmax, Trfinal, or both

  4. Mechanistic studies of cancer cell mitochondria- and NQO1-mediated redox activation of beta-lapachone, a potentially novel anticancer agent

    SciTech Connect

    Li, Jason Z.; Ke, Yuebin; Misra, Hara P.; Trush, Michael A.; Li, Y. Robert; Zhu, Hong; Jia, Zhenquan

    2014-12-15

    Beta-lapachone (beta-Lp) derived from the Lapacho tree is a potentially novel anticancer agent currently under clinical trials. Previous studies suggested that redox activation of beta-Lp catalyzed by NAD(P)H:quinone oxidoreductase 1 (NQO1) accounted for its killing of cancer cells. However, the exact mechanisms of this effect remain largely unknown. Using chemiluminescence and electron paramagnetic resonance (EPR) spin-trapping techniques, this study for the first time demonstrated the real-time formation of ROS in the redox activation of beta-lapachone from cancer cells mediated by mitochondria and NQO1 in melanoma B16–F10 and hepatocellular carcinoma HepG2 cancer cells. ES936, a highly selective NQO1 inhibitor, and rotenone, a selective inhibitor of mitochondrial electron transport chain (METC) complex I were found to significantly block beta-Lp meditated redox activation in B16–F10 cells. In HepG2 cells ES936 inhibited beta-Lp-mediated oxygen radical formation by ∼ 80% while rotenone exerted no significant effect. These results revealed the differential contribution of METC and NQO1 to beta-lapachone-induced ROS formation and cancer cell killing. In melanoma B16–F10 cells that do not express high NQO1 activity, both NOQ1 and METC play a critical role in beta-Lp redox activation. In contrast, in hepatocellular carcinoma HepG2 cells expressing extremely high NQO1 activity, redox activation of beta-Lp is primarily mediated by NQO1 (METC plays a minor role). These findings will contribute to our understanding of how cancer cells are selectively killed by beta-lapachone and increase our ability to devise strategies to enhance the anticancer efficacy of this potentially novel drug while minimizing its possible adverse effects on normal cells. - Highlights: • Both isolated mitochondria and purified NQO1 are able to generate ROS by beta-Lp. • The differential roles of mitochondria and NQO1 in mediating redox activation of beta-Lp • In cancer cells with

  5. Solvent, anion, and structural effects on the redox potentials and UV-visible spectral properties of mononuclear manganese corroles.

    PubMed

    Shen, Jing; El Ojaimi, Maya; Chkounda, Mohammed; Gros, Claude P; Barbe, Jean-Michel; Shao, Jianguo; Guilard, Roger; Kadish, Karl M

    2008-09-01

    A series of manganese(III) corroles were investigated as to their electrochemistry and spectroelectrochemistry in nonaqueous solvents. Up to three oxidations and one reduction were obtained for each complex depending on the solvents. The main compound discussed in this paper is the meso-substituted manganese corrole, (Mes 2PhCor)Mn, and the main points are how changes in axially coordinated anion and solvent will affect the redox potentials and UV-vis spectra of each electrogenerated species in oxidation states of Mn(III), Mn(IV), or Mn(II). The anions OAc (-), Cl (-), CN (-), and SCN (-) were found to form five-coordinate complexes with the neutral Mn(III) corrole while two OH (-) or F (-) anions were shown to bind axially in a stepwise addition to give the five- and six-coordinate complexes in nonaqueous media. In each case, complexation with one or two anionic axial ligands led to an easier oxidation and a harder reduction as compared to the uncomplexed four-coordinate species.

  6. Redox potential tuning through differential quinone binding in the photosynthetic reaction center of Rhodobacter sphaeroides

    SciTech Connect

    Vermaas, Josh V.; Taguchi, Alexander T.; Dikanov, Sergei A.; Wraight, Colin A.; Tajkhorshid, Emad

    2015-03-03

    Ubiquinone forms an integral part of the electron transport chain in cellular respiration and photosynthesis across a vast number of organisms. Prior experimental results have shown that the photosynthetic reaction center (RC) from Rhodobacter sphaeroides is only fully functional with a limited set of methoxy-bearing quinones, suggesting that specific interactions with this substituent are required to drive electron transport and the formation of quinol. The nature of these interactions has yet to be determined. Through parameterization of a CHARMM-compatible quinone force field and subsequent molecular dynamics simulations of the quinone-bound RC, in this paper we have investigated and characterized the interactions of the protein with the quinones in the QA and QB sites using both equilibrium simulation and thermodynamic integration. In particular, we identify a specific interaction between the 2-methoxy group of ubiquinone in the QB site and the amide nitrogen of GlyL225 that we implicate in locking the orientation of the 2-methoxy group, thereby tuning the redox potential difference between the quinones occupying the QA and QB sites. Finally, disruption of this interaction leads to weaker binding in a ubiquinone analogue that lacks a 2-methoxy group, a finding supported by reverse electron transfer electron paramagnetic resonance experiments of the QA–QB– biradical and competitive binding assays.

  7. Middle-redox potential laccase from Ganoderma sp.: its application in improvement of feed for monogastric animals

    PubMed Central

    Sharma, Krishna Kant; Shrivastava, Bhuvnesh; Sastry, V. R. B.; Sehgal, Neeta; Kuhad, Ramesh Chander

    2013-01-01

    The variables influencing laccase production by white-rot fungus Ganoderma sp. rckk-02 were optimized employing response surface methodology. Malt extract (6.0% w/v), lignin (0.5% w/v) and pH (5.5) were found to be the most significant factors for enhanced laccase production by 7 fold (226.0 U/ml) as compared to unoptimized growth conditions (32.0 U/ml). The N-terminal sequence of laccase revealed its distinct amino acid profile (S- I- R- N- S- G), which suggested it as a novel enzyme. The Far-UV CD spectrum of the laccase showed single broad negative trough at around 213 nm, a typical signature of all β proteins. The laccase was found to fall in the range of middle redox potential laccases. Purified laccase at dosage of 2.5 Ug−1 body weight when supplemented with pelleted diet of rats, a significant improvement (p < 0.05) in nutrients digestibility without causing any elevation of blood stress enzymes was observed. PMID:23416696

  8. [Effect of disulfiram on energy metabolism (redox potential shift) coupled to paradoxical sleep episodes in rat cerebral cortex].

    PubMed

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

    2012-01-01

    Disulfiram (DS) is widely used to treat patients with chronic alcoholism. DS treatment multiplies PS episodes. In this work, DS effect on the number of PS episodes and on the energy metabolism changes in the cerebral cortex (coupled to PS episodes) was investigated for the first time in rats. Polygraphic recording of the redox potential E (with platinum electrodes implanted in several cortical sites), electrocorticogram, neck electromyogram, and general motor activity were made in sleep-wake cycles. Rats received DS (100 mg/kg) with meals for two nights, after which the number of PS episodes increased almost twice during two subsequent sessions (prior to receiving DS). This was evidence of an increase in PS pressure coupled to a decrease of norepinephrine level in the brain. DS also evoked sharp decrease in the amount of the positive E shifts related to PS, which were replaced by the negative E shifts or by the two-phase E shifts (negative-positive waves). The absolute mean amplitude decreased both for the positive E shifts and the negative E shifts. These findings demonstrate prevailing glycolytic compartment as a source of fuel supporting PS and the inhibition in all brain energetic compartments. The data presented well agree with the conception that glycolysis becomes the main source for the brain activity under pathology conditions.

  9. Redox potential of the terminal quinone electron acceptor QB in photosystem II reveals the mechanism of electron transfer regulation

    PubMed Central

    Kato, Yuki; Nagao, Ryo; Noguchi, Takumi

    2016-01-01

    Photosystem II (PSII) extracts electrons from water at a Mn4CaO5 cluster using light energy and then transfers them to two plastoquinones, the primary quinone electron acceptor QA and the secondary quinone electron acceptor QB. This forward electron transfer is an essential process in light energy conversion. Meanwhile, backward electron transfer is also significant in photoprotection of PSII proteins. Modulation of the redox potential (Em) gap of QA and QB mainly regulates the forward and backward electron transfers in PSII. However, the full scheme of electron transfer regulation remains unresolved due to the unknown Em value of QB. Here, for the first time (to our knowledge), the Em value of QB reduction was measured directly using spectroelectrochemistry in combination with light-induced Fourier transform infrared difference spectroscopy. The Em(QB−/QB) was determined to be approximately +90 mV and was virtually unaffected by depletion of the Mn4CaO5 cluster. This insensitivity of Em(QB−/QB), in combination with the known large upshift of Em(QA−/QA), explains the mechanism of PSII photoprotection with an impaired Mn4CaO5 cluster, in which a large decrease in the Em gap between QA and QB promotes rapid charge recombination via QA−. PMID:26715751

  10. Tetrodotoxin Blockade on Canine Cardiac L-Type Ca2+ Channels Depends on pH and Redox Potential

    PubMed Central

    Hegyi, Bence; Komáromi, István; Kistamás, Kornél; Ruzsnavszky, Ferenc; Váczi, Krisztina; Horváth, Balázs; Magyar, János; Bányász, Tamás; Nánási, Péter P.; Szentandrássy, Norbert

    2013-01-01

    Tetrodotoxin (TTX) is believed to be one of the most selective inhibitors of voltage-gated fast Na+ channels in excitable tissues. Recently, however, TTX has been shown to block L-type Ca2+ current (ICa) in canine cardiac cells. In the present study, the TTX-sensitivity of ICa was studied in isolated canine ventricular myocytes as a function of (1) channel phosphorylation, (2) extracellular pH and (3) the redox potential of the bathing medium using the whole cell voltage clamp technique. Fifty-five micromoles of TTX (IC50 value obtained under physiological conditions) caused 60% ± 2% inhibition of ICa in acidic (pH = 6.4), while only a 26% ± 2% block in alkaline (pH = 8.4) milieu. Similarly, the same concentration of TTX induced 62% ± 6% suppression of ICa in a reductant milieu (containing glutathione + ascorbic acid + dithiothreitol, 1 mM each), in contrast to the 31% ± 3% blockade obtained in the presence of a strong oxidant (100 μM H2O2). Phosphorylation of the channel protein (induced by 3 μM forskolin) failed to modify the inhibiting potency of TTX; an IC50 value of 50 ± 4 μM was found in forskolin. The results are in a good accordance with the predictions of our model, indicating that TTX binds, in fact, to the selectivity filter of cardiac L-type Ca channels. PMID:23771047

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

    PubMed

    Singh, S N

    2001-10-01

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

  12. Different Contribution of Redox-Sensitive Transient Receptor Potential Channels to Acetaminophen-Induced Death of Human Hepatoma Cell Line

    PubMed Central

    Badr, Heba; Kozai, Daisuke; Sakaguchi, Reiko; Numata, Tomohiro; Mori, Yasuo

    2016-01-01

    Acetaminophen (APAP) is a safe analgesic antipyretic drug at prescribed doses. Its overdose, however, can cause life-threatening liver damage. Though, involvement of oxidative stress is widely acknowledged in APAP-induced hepatocellular death, the mechanism of this increased oxidative stress and the associated alterations in Ca2+ homeostasis are still unclear. Among members of transient receptor potential (TRP) channels activated in response to oxidative stress, we here identify that redox-sensitive TRPV1, TRPC1, TRPM2, and TRPM7 channels underlie Ca2+ entry and downstream cellular damages induced by APAP in human hepatoma (HepG2) cells. Our data indicate that APAP treatment of HepG2 cells resulted in increased reactive oxygen species (ROS) production, glutathione (GSH) depletion, and Ca2+ entry leading to increased apoptotic cell death. These responses were significantly suppressed by pretreatment with the ROS scavengers N-acetyl-L-cysteine (NAC) and 4,5-dihydroxy-1,3-benzene disulfonic acid disodium salt monohydrate (Tiron), and also by preincubation of cells with the glutathione inducer Dimethylfumarate (DMF). TRP subtype-targeted pharmacological blockers and siRNAs strategy revealed that suppression of either TRPV1, TRPC1, TRPM2, or TRPM7 reduced APAP-induced ROS formation, Ca2+ influx, and cell death; the effects of suppression of TRPV1 or TRPC1, known to be activated by oxidative cysteine modifications, were stronger than those of TRPM2 or TRPM7. Interestingly, TRPV1 and TRPC1 were labeled by the cysteine-selective modification reagent, 5,5′-dithiobis (2-nitrobenzoic acid)-2biotin (DTNB-2Bio), and this was attenuated by pretreatment with APAP, suggesting that APAP and/or its oxidized metabolites act directly on the modification target cysteine residues of TRPV1 and TRPC1 proteins. In human liver tissue, TRPV1, TRPC1, TRPM2, and TRPM7 channels transcripts were localized mainly to hepatocytes and Kupffer cells. Our findings strongly suggest that APAP

  13. Arsenic exposure, inflammation, and renal function in Bangladeshi adults: effect modification by plasma glutathione redox potential

    PubMed Central

    Peters, Brandilyn A.; Liu, Xinhua; Hall, Megan N.; Ilievski, Vesna; Slavkovich, Vesna; Siddique, Abu B.; Alam, Shafiul; Islam, Tariqul; Graziano, Joseph H.; Gamble, Mary V.

    2015-01-01

    Exposure to arsenic (As) in drinking water is a widespread public health problem leading to increased risk for multiple outcomes such as cancer, cardiovascular disease, and possibly renal disease; potential mechanisms include inflammation and oxidative stress. We tested the hypothesis that As exposure is associated with increased inflammation and decreased estimated glomerular filtration rate (eGFR) and examined whether the effects of As were modified by plasma glutathione (GSH), glutathione disulfide (GSSG), or the reduction potential of the GSSG/2GSH pair (EhGSH). In a cross-sectional study of N = 374 Bangladeshi adults having a wide range of As exposure, we measured markers of inflammation (plasma C-reactive protein (CRP), α-1 acid glycoprotein (AGP)), renal function (eGFR), GSH, and GSSG. In covariate-adjusted models, a 10% increase in water As, urinary As adjusted for specific gravity (uAs), or blood As (bAs) was associated with a 0.74% (p = 0.01), 0.90% (p = 0.16), and 1.39% (p = 0.07) increase in CRP, respectively; there was no association with AGP. A 10% increase in uAs or bAs was associated with an average reduction in eGFR of 0.16 (p = 0.12) and 0.21 ml/min/1.73 m2 (p = 0.08), respectively. In stratified analyses, the effect of As exposure on CRP was observed only in participants having EhGSH > median (uAs pWald = 0.03; bAs pWald = 0.05). This was primarily driven by stronger effects of As exposure on CRP in participants with lower plasma GSH. The effects of As exposure on eGFR were not modified significantly by EhGSH, GSH, or GSSG. These data suggest that participants having lower plasma GSH and a more oxidized plasma EhGSH are at increased risk for As-induced inflammation. Future studies should evaluate whether antioxidant treatment lowers plasma EhGSH and reduces risk for As-induced diseases. PMID:25916185

  14. Electron flow in multiheme bacterial cytochromes is a balancing act between heme electronic interaction and redox potentials

    PubMed Central

    Breuer, Marian; Rosso, Kevin M.; Blumberger, Jochen

    2014-01-01

    The naturally widespread process of electron transfer from metal reducing bacteria to extracellular solid metal oxides entails unique biomolecular machinery optimized for long-range electron transport. To perform this function efficiently, microorganisms have adapted multiheme c-type cytochromes to arrange heme cofactors into wires that cooperatively span the cellular envelope, transmitting electrons along distances greater than 100 Å. Implications and opportunities for bionanotechnological device design are self-evident. However, at the molecular level, how these proteins shuttle electrons along their heme wires, navigating intraprotein intersections and interprotein interfaces efficiently, remains a mystery thus far inaccessible to experiment. To shed light on this critical topic, we carried out extensive quantum mechanics/molecular mechanics simulations to calculate stepwise heme-to-heme electron transfer rates in the recently crystallized outer membrane deca-heme cytochrome MtrF. By solving a master equation for electron hopping, we estimate an intrinsic, maximum possible electron flux through solvated MtrF of 104–105 s−1, consistent with recently measured rates for the related multiheme protein complex MtrCAB. Intriguingly, our calculations show that the rapid electron transport through MtrF is the result of a clear correlation between heme redox potential and the strength of electronic coupling along the wire: thermodynamically uphill steps occur only between electronically well-connected stacked heme pairs. This observation suggests that the protein evolved to harbor low-potential hemes without slowing down electron flow. These findings are particularly profound in light of the apparently well-conserved staggered cross-heme wire structural motif in functionally related outer membrane proteins. PMID:24385579

  15. Age-related alterations of plasma glutathione and oxidation of redox potentials in chimpanzee (Pan troglodytes) and rhesus monkey (Macaca mulatta).

    PubMed

    Paredes, Jamespaul; Jones, Dean P; Wilson, Mark E; Herndon, James G

    2014-04-01

    Chimpanzee (Pan troglodytes) and rhesus macaque (Macaca mulatta) and humans (Homo sapiens) share physiological and genetic characteristics, but have remarkably different life spans, with chimpanzees living 50-60 % and the rhesus living 35-40 % of maximum human survival. Since oxidative processes are associated with aging and longevity, we might expect to see species differences in age-related oxidative processes. Blood and extracellular fluid contain two major thiol redox nodes, glutathione (GSH)/glutathione-disulfide (GSSG) and cysteine (Cys)/cystine (CySS), which are subject to reversible oxidation-reduction reactions and are maintained in a dynamic non-equilibrium state. Disruption of these thiol redox nodes leads to oxidation of their redox potentials (EhGSSG and EhCySS) which affects cellular physiology and is associated with aging and the development of chronic diseases in humans. The purpose of this study was to measure age-related changes in these redox thiols and their corresponding redox potentials (Eh) in chimpanzees and rhesus monkeys. Our results show similar age-related decreases in the concentration of plasma GSH and Total GSH as well as oxidation of the EhGSSG in male and female chimpanzees. Female chimpanzees and female rhesus monkeys also were similar in several outcome measures. For example, similar age-related decreases in the concentration of plasma GSH and Total GSH, as well as age-related oxidation of the EhGSSG were observed. The data collected from chimpanzees and rhesus monkeys corroborates previous reports on oxidative changes in humans and confirms their value as a comparative reference for primate aging.

  16. Green chemistry methods in sulfur dyeing: application of various reducing D-sugars and analysis of the importance of optimum redox potential.

    PubMed

    Blackburn, Richard S; Harvey, Anna

    2004-07-15

    The importance of sulfur dyeing of cellulosic fibers, particularly cotton, is realized economically throughout the dyeing industry. At the present time, dyeing with sulfur dyes requires the use of various auxiliaries, many of which have adverse effects on the environment. The most damaging of these is the reducing agent sodium sulfide, required to reduce the dye molecules to a water-soluble leuco form to enable adsorption and diffusion into the fiber. In this study, attempts have been made to replace the sodium sulfide used within the sulfur dyeing process with a variety of environmentally friendly reducing sugars. The redox potential of various hexose and pentose monosaccharides and reducing disaccharides was recorded and compared. Subsequently, cotton was dyed with the world's most important sulfur dye, C. I. Sulfur Black 1, using the reducing sugars under alkaline conditions, and compared to dyeings secured by employing commercial sulfide reducing agents. It was observed that reducing sugars gave comparable, and in many cases superior, color strength and wash fastness results, with respect to the commercial sulfide-based reducing agents, which still account for the vast majority of sulfur dyeing processes and that pose significant environmental concern. Employment of reducing sugars in sulfur dyeing could provide a sustainable, nontoxic, biodegradable, cost-effective alternative to sodium polysulfide and sodium hydrogen sulfide. Comparison of the redox potential of reducing sugars against the color strength of the dyeings secured demonstrated that there was an optimum redox potential of around -650 mV for maximum color strength achieved. The same redox potential also conferred the lowest color loss upon washing. These observations were attributed to reduction of the polymeric dye molecules to an optimum size for fiber affinity and diffusion into the fiber, but which would also confer maximum wash fastness upon oxidation.

  17. 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

  18. Mycobacterium tuberculosis WhiB3 Responds to Vacuolar pH-induced Changes in Mycothiol Redox Potential to Modulate Phagosomal Maturation and Virulence.

    PubMed

    Mehta, Mansi; Rajmani, Raju S; Singh, Amit

    2016-02-05

    The ability of Mycobacterium tuberculosis to resist intraphagosomal stresses, such as oxygen radicals and low pH, is critical for its persistence. Here, we show that a cytoplasmic redox sensor, WhiB3, and the major M. tuberculosis thiol, mycothiol (MSH), are required to resist acidic stress during infection. WhiB3 regulates the expression of genes involved in lipid anabolism, secretion, and redox metabolism, in response to acidic pH. Furthermore, inactivation of the MSH pathway subverted the expression of whiB3 along with other pH-specific genes in M. tuberculosis. Using a genetic biosensor of mycothiol redox potential (EMSH), we demonstrated that a modest decrease in phagosomal pH is sufficient to generate redox heterogeneity in EMSH of the M. tuberculosis population in a WhiB3-dependent manner. Data indicate that M. tuberculosis needs low pH as a signal to alter cytoplasmic EMSH, which activates WhiB3-mediated gene expression and acid resistance. Importantly, WhiB3 regulates intraphagosomal pH by down-regulating the expression of innate immune genes and blocking phagosomal maturation. We show that this block in phagosomal maturation is in part due to WhiB3-dependent production of polyketide lipids. Consistent with these observations, MtbΔwhiB3 displayed intramacrophage survival defect, which can be rescued bypharmacological inhibition of phagosomal acidification. Last, MtbΔwhiB3 displayed marked attenuation in the lungs of guinea pigs. Altogether, our study revealed an intimate link between vacuolar acidification, redox physiology, and virulence in M. tuberculosis and discovered WhiB3 as crucial mediator of phagosomal maturation arrest and acid resistance in M. tuberculosis.

  19. Impact of Proximal and Distal Pocket Site-Directed Mutations on the Ferric/Ferrous Heme Redox Potential of Yeast Cytochrome-c-Peroxidase

    PubMed Central

    Goodin, D. B.

    2012-01-01

    Cytochrome-c-peroxidase (CCP) contains a five-coordinate heme active site. The reduction potential for the ferric to ferrous couple in CCP is anomalously low and pH dependent (Eo = ~−180 mV vs. S.H.E. at pH 7). The contribution of the protein environment to the tuning of the redox potential of this couple is evaluated using site directed mutants of several amino acid residues in the environment of the heme. These include proximal pocket mutation to residues Asp-235, Trp-191, Phe-202 and His-175, distal pocket mutation to residues Trp-51, His-52, and Arg-48; and a heme edge mutation to Ala-147. Where unknown, the structural changes resulting from the amino acid substitution have been studied by X-ray crystallography. In most cases, ostensibly polar or charged residues are replaced by large hydrophobic groups or alternatively by Ala or Gly. These latter have been shown to generate large, solvent filled cavities. Reduction potentials are measured as a function of pH by spectroelectrochemistry. Starting with the X-ray derived structures of CCP and the mutants, or with predicted structures generated by Molecular Dynamics (MD), predictions of redox potential changes are modeled using the Protein Dipoles Langevin Dipoles (PDLD) method. These calculations serve to model an electrostatic assessment of the redox potential change with simplified assumptions about heme iron chemistry, with the balance of the experimentally observed shifts in redox potential being thence attributed to changes in the ligand set and heme coordination chemistry, and/or other changes in the structure not directly evident in the X-ray structures (e.g. ionization states, specific roles played by solvent species, or conformationally flexible portions of the protein). Agreement between theory and experiment is good for all mutant proteins with the exception of the mutation Arg 48 to Ala, and His 52 to Ala. In the former case, the influence of phosphate buffer is adduced to account for the discrepancy

  20. Electronic structure and energy decomposition analyses as a tool to interpret the redox potential ranking of naphtho-, biphenyl- and biphenylene-quinone isomers.

    PubMed

    Tomerini, D; Politano, O; Gatti, C; Frayret, C

    2016-09-29

    By calling on modelling approaches we have performed a comparative study on the redox properties of various naphtho-, biphenyl- and biphenylene-quinone isomers. These different compounds exhibit as a whole a redox potential range between 2.09 and 2.90 V vs. Li(+)/Li. A specific methodology was used to decrypt the interplay among isomerism, aromaticity and antiaromaticity modifications and the stabilization/destabilization effects due to other molecular components on this key electrochemical feature for electrode materials of batteries. In particular, energy decomposition analysis, within the Quantum Theory of Atoms in Molecules, along with the electron and electron spin population changes upon reduction nicely rationalise the observed potential trends. While 1,2- and 2,3-isomers show the highest/lowest redox potential in the biphenylene-quinone series, a reverse trend is observed for the naphtho-quinone, the compound having the two carbonyl groups on distinct rings being characterized by an intermediate value in both cases. There is instead almost no differentiation between 1,2 and 2,3 isomers for the biphenyl-quinone family.

  1. Real-time monitoring of the extracellular redox potential of cell suspensions during plant/bacterial interactions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In plants and animals, there has been a strong focus on reactive oxygen species/antioxidants in regard to stress responses. This has lead to an awareness of the importance of ‘redox potential’ as a prime regulatory determinant of cellular function and responses to internal and external stimuli. I...

  2. Potential application of microbial iron redox cycles in nitrate removal and their effects on clay mineral properties

    NASA Astrophysics Data System (ADS)

    Zhao, L.; Dong, H.; Kukkadapu, R. K.; Briggs, B. R.; Zeng, Q.

    2014-12-01

    Phyllosilicates that are ubiquitous in subsurface can serve as an iron source for microbial respiration. The objective of this research is to determine the ability of the phyllosilicate Fe to remove nitrate in subsurface undergoing microbial-driven redox cycles. In this study, thus, a well-characterized reference clay (NAu-2; nontronite), was subjected to redox cycles in a system containing dissimilatory Fe(III)-reducing bacteria, Shewanella putrefaciens CN32, and nitrate-dependent Fe(II)-oxidizing bacteria, Pseudogulbenkiania sp. Strain 2002. Three redox cycles were conducted in bicarbonate- and PIPES-buffered medium. The extents of Fe(III) reduction, Fe(II) oxidation, nitrate reduction, and its various intermediate products were measured by wet chemical methods. For each cycle, Electron Energy Loss Spectroscopy and Mossbauer spectroscopy confirmed Fe oxidation state. Mineralogical changes were identified by using X-ray diffraction (XRD), 57Fe-Mössbauer spectroscopy, and infrared absorption spectroscopy. For all three cycles, nitrate was completely reduced to nitrogen gas under both bicarbonate- and PIPES- buffered conditions. As redox cycle increased, bio-reduction extents of Fe(III) in NAu-2 decreased by 33% and 48% in PIPES- and bicarbonate-buffered medium, respectively; however, bio-oxidation extents increased by 66% and 55% in the same medium, respectively. Despite the change of OH-stretching vibration band and OH-bending vibration bands in NAu-2 structure along Fe redox cycles, XRD data showed interlayer spacing of NAu-2 to be constant along the same Fe redox cycle. 57Fe-Mössbauer spectroscopy indicated complex reduction and re-oxidation pathways. For example, a distinct Fe(II) doublet and a Fe2.5+ feature due to interfacial Fe(II)-Fe(III) electron transfer on clay mineral are prominent in their RT spectra. Both these Fe(II) are partially oxidized by Fe(II)-oxidizing bacteria. The result of this study shows that Fe in biogenically reduced or oxidized NAu-2

  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

    2014-01-07

    It is well-established that redox-reactions are integral to biology for energy harvesting (oxidative phosphorylation), immune defense (oxidative burst) and drug metabolism (phase I reactions), yet there is emerging evidence that redox may play broader roles in biology (e.g., redox signaling). A critical challenge is the need for tools that can probe biologically-relevant redox interactions simply, rapidly and without the need for a comprehensive suite of analytical methods. We propose that electrochemistry may provide such a tool. In this tutorial review, we describe recent studies with a redox-capacitor film that can serve as a bio-electrode interface that can accept, store and donate electrons from mediators commonly used in electrochemistry and also in biology. Specifically, we (i) describe the fabrication of this redox-capacitor from catechols and the polysaccharide chitosan, (ii) discuss the mechanistic basis for electron exchange, (iii) illustrate the properties of this redox-capacitor and its capabilities for promoting redox-communication between biology and electrodes, and (iv) suggest the potential for enlisting signal processing strategies to "extract" redox information. We believe these initial studies indicate broad possibilities for enlisting electrochemistry and signal processing to acquire "systems level" redox information from biology.

  4. Redox potentials of primary electron acceptor quinone molecule (QA)- and conserved energetics of photosystem II in cyanobacteria with chlorophyll a and chlorophyll d.

    PubMed

    Allakhverdiev, Suleyman I; Tsuchiya, Tohru; Watabe, Kazuyuki; Kojima, Akane; Los, Dmitry A; Tomo, Tatsuya; Klimov, Vyacheslav V; Mimuro, Mamoru

    2011-05-10

    In a previous study, we measured the redox potential of the primary electron acceptor pheophytin (Phe) a of photosystem (PS) II in the chlorophyll d-dominated cyanobacterium Acaryochloris marina and a chlorophyll a-containing cyanobacterium, Synechocystis. We obtained the midpoint redox potential (E(m)) values of -478 mV for A. marina and -536 mV for Synechocystis. In this study, we measured the redox potentials of the primary electron acceptor quinone molecule (Q(A)), i.e., E(m)(Q(A)/Q(A)(-)), of PS II and the energy difference between [P680·Phe a(-)·Q(A)] and [P680·Phe a·Q(A)(-)], i.e., ΔG(PhQ). The E(m)(Q(A)/Q(A)(-)) of A. marina was determined to be +64 mV without the Mn cluster and was estimated to be -66 to -86 mV with a Mn-depletion shift (130-150 mV), as observed with other organisms. The E(m)(Phe a/Phe a(-)) in Synechocystis was measured to be -525 mV with the Mn cluster, which is consistent with our previous report. The Mn-depleted downshift of the potential was measured to be approximately -77 mV in Synechocystis, and this value was applied to A. marina (-478 mV); the E(m)(Phe a/Phe a(-)) was estimated to be approximately -401 mV. These values gave rise to a ΔG(PhQ) of -325 mV for A. marina and -383 mV for Synechocystis. In the two cyanobacteria, the energetics in PS II were conserved, even though the potentials of Q(A)(-) and Phe a(-) were relatively shifted depending on the special pair, indicating a common strategy for electron transfer in oxygenic photosynthetic organisms.

  5. Critical roles of Asp40 at the haem proximal side of haem-regulated phosphodiesterase from Escherichia coli in redox potential, auto-oxidation and catalytic control.

    PubMed

    Watanabe, Miki; Kurokawa, Hirofumi; Yoshimura-Suzuki, Tokiko; Sagami, Ikuko; Shimizu, Toru

    2004-10-01

    In haem-regulated phosphodiesterase (PDE) from Escherichia coli (Ec DOS), haem is bound to the PAS domain, and the redox state of the haem iron regulates catalysis by the PDE domain. We generated mutants of Asp40, which forms a hydrogen bond with His77 (a proximal haem axial ligand) via two water molecules, and a salt bridge with Arg85 at the protein surface. The redox potential of haem was markedly increased from 67 mV vs. the standard hydrogen electrode in the wild-type enzyme to 95 mV and 114 mV in the Ala and Asn mutants, respectively. Additionally, the auto-oxidation rate of Ec DOS PAS was significantly increased from 0.0053 to 0.051 and 0.033 min(-1), respectively. Interestingly, the catalytic activities of the Asp40 mutants were abolished completely. Thus, Asp40 appears to play a critical role in the electronic structure of the haem iron and redox-dependent catalytic control of the PDE domain. In this report, we discuss the mechanism of catalytic control of Ec DOS, based on the physico-chemical characteristics of the Asp40 mutants.

  6. Redox dynamics in the active layer of an Arctic headwater catchment; examining the potential for transfer of dissolved methane from soils to stream water

    NASA Astrophysics Data System (ADS)

    Street, Lorna E.; Dean, Joshua F.; Billett, Michael F.; Baxter, Robert; Dinsmore, Kerry J.; Lessels, Jason S.; Subke, Jens-Arne; Tetzlaff, Doerthe; Wookey, Philip A.

    2016-11-01

    The linkages between methane production, transport, and release from terrestrial and aquatic systems are not well understood, complicating the task of predicting methane emissions. We present novel data examining the potential for the saturated zone of active layer soils to act as a source of dissolved methane to the aquatic system, via soil water discharge, within a headwater catchment of the continuous permafrost zone in Northern Canada. We monitored redox conditions and soil methane concentrations across a transect of soil profiles from midstream to hillslope and compare temporal patterns in methane concentrations in soils to those in the stream. We show that redox conditions in active layer soils become more negative as the thaw season progresses, providing conditions suitable for net methanogenesis and that redox conditions are sensitive to increased precipitation during a storm event—but only in shallower surface soil layers. While we demonstrate that methane concentrations at depth in the hillslope soils increase over the course of the growing season as reducing conditions develop, we find no evidence that this has an influence on stream water methane concentrations. Sediments directly beneath the stream bed, however, remain strongly reducing at depth throughout the thaw season and contain methane at concentrations 5 orders of magnitude greater than those in hillslope soils. The extent of substreambed methane sources, and the rates of methane transport from these zones, may therefore be important factors determining headwater stream methane concentrations under changing Arctic hydrologic regimes.

  7. The Redox Potential of the Plastoquinone Pool of the Cyanobacterium Synechocystis Species Strain PCC 6803 Is under Strict Homeostatic Control1[C][W

    PubMed Central

    Schuurmans, R. Milou; Schuurmans, J. Merijn; Bekker, Martijn; Kromkamp, Jacco C.; Matthijs, Hans C.P.; Hellingwerf, Klaas J.

    2014-01-01

    A method is presented for rapid extraction of the total plastoquinone (PQ) pool from Synechocystis sp. strain PCC 6803 cells that preserves the in vivo plastoquinol (PQH2) to -PQ ratio. Cells were rapidly transferred into ice-cold organic solvent for instantaneous extraction of the cellular PQ plus PQH2 content. After high-performance liquid chromatography fractionation of the organic phase extract, the PQH2 content was quantitatively determined via its fluorescence emission at 330 nm. The in-cell PQH2-PQ ratio then followed from comparison of the PQH2 signal in samples as collected and in an identical sample after complete reduction with sodium borohydride. Prior to PQH2 extraction, cells from steady-state chemostat cultures were exposed to a wide range of physiological conditions, including high/low availability of inorganic carbon, and various actinic illumination conditions. Well-characterized electron-transfer inhibitors were used to generate a reduced or an oxidized PQ pool for reference. The in vivo redox state of the PQ pool was correlated with the results of pulse-amplitude modulation-based chlorophyll a fluorescence emission measurements, oxygen exchange rates, and 77 K fluorescence emission spectra. Our results show that the redox state of the PQ pool of Synechocystis sp. strain PCC 6803 is subject to strict homeostatic control (i.e. regulated between narrow limits), in contrast to the more dynamic chlorophyll a fluorescence signal. PMID:24696521

  8. Postnatal exposure to trichloroethylene alters glutathione redox homeostasis, methylation potential, and neurotrophin expression in the mouse hippocampus

    PubMed Central

    Blossom, Sarah J.; Melnyk, Stepan; Cooney, Craig A.; Gilbert, Kathleen M.; James, S. Jill

    2012-01-01

    Previous studies have shown that continuous exposure throughout gestation until the juvenile period to environmentally-relevant doses of trichloroethylene (TCE) in the drinking water of MRL+/+ mice promoted adverse behavior associated with glutathione depletion in the cerebellum indicating increased sensitivity to oxidative stress. The purpose of this study was to extend our findings and further characterize the impact of TCE exposure on redox homeostasis and biomarkers of oxidative stress in the hippocampus, a brain region prone to oxidative stress. Instead of a continuous exposure, the mice were exposed to water only or two environmentally relevant doses of TCE in the drinking water postnatally from birth until 6 weeks of age. Biomarkers of plasma metabolites in the transsulfuration pathway and the transmethylation pathway of the methionine cycle were also examined. Gene expression of neurotrophins was examined to investigate a possible relationship between oxidative stress, redox imbalance and neurotrophic factor expression with TCE exposure. Our results show that hippocampi isolated from male mice exposed to TCE showed altered glutathione redox homeostasis indicating a more oxidized state. Also observed was a significant, dose dependent increase in glutathione precursors. Plasma from the TCE treated mice showed alterations in metabolites in the transsulfuration and transmethylation pathways indicating redox imbalance and altered methylation capacity. 3-Nitrotyrosine, a biomarker of protein oxidative stress, was also significantly higher in plasma and hippocampus of TCE-exposed mice compared to controls. In contrast, expression of key neurotrophic factors in the hippocampus (BDNF, NGF, and NT-3) was significantly reduced compared to controls. Our results demonstrate that low-level postnatal and early life TCE exposure modulates neurotrophin gene expression in the mouse hippocampus and may provide a mechanism for TCE-mediated neurotoxicity. PMID:22421312

  9. Phenolic contents and bioactive potential of peach fruit extracts.

    PubMed

    Mokrani, Abderrahmane; Krisa, Stéphanie; Cluzet, Stéphanie; Da Costa, Grégory; Temsamani, Hamza; Renouf, Elodie; Mérillon, Jean-Michel; Madani, Khodir; Mesnil, Marc; Monvoisin, Arnaud; Richard, Tristan

    2016-07-01

    Several cultivars of peach fruit (Prunus persica L.) were investigated. Their phenolic composition and concentration were assessed by LC-MS. Concentrations were calculated in mg per g of dry weight extract. Their antioxidant capacity (Folin-Ciocalteu, ORAC, DPPH, ABTS, PFRAP and ICA), inhibitory property against β-amyloid and α-synuclein fibril formation and protective capacity against Aβ-induced toxicity on PC12 cell lines (viability assessed by MTT assay and intracellular ROS production by DCFH-DA assay) were evaluated. Fifteen different phenolic compounds were identified and quantified. In particular, new isorhamnetin derivatives were identified. Phenolic contents were ranged between 19 and 82mg/g. Spring Belle extract had the highest content and Romea the lowest. Except for the ICA assay, a good correlation between phenolic content and the antioxidant capacities of peach fruit extracts was found, indicating that phenolic compounds are major contributors to their antioxidant capacity. Results indicate that the phenolic extract of peach cultivars inhibits Aβ and αS fibril formation and protects PC12 cell lines against Aβ-induced toxicity.

  10. Determination of formal redox potentials in aqueous solution of copper(II) complexes with ligands having nitrogen and oxygen donor atoms and comparison with their EPR and UV-Vis spectral features.

    PubMed

    Tabbì, Giovanni; Giuffrida, Alessandro; Bonomo, Raffaele P

    2013-11-01

    Formal redox potentials in aqueous solution were determined for copper(II) complexes with ligands having oxygen and nitrogen as donor atoms. All the chosen copper(II) complexes have well-known stereochemistries (pseudo-octahedral, square planar, square-based pyramidal, trigonal bipyramidal or tetrahedral) as witnessed by their reported spectroscopic, EPR and UV-visible (UV-Vis) features, so that a rough correlation between the measured redox potential and the typical geometrical arrangement of the copper(II) complex could be established. Negative values have been obtained for copper(II) complexes in tetragonally elongated pseudo-octahedral geometries, when measured against Ag/AgCl reference electrode. Copper(II) complexes in tetrahedral environments (or flattened tetrahedral geometries) show positive redox potential values. There is a region, always in the field of negative redox potentials which groups the copper(II) complexes exhibiting square-based pyramidal arrangements. Therefore, it is suggested that a measurement of the formal redox potential could be of great help, when some ambiguities might appear in the interpretation of spectroscopic (EPR and UV-Vis) data. Unfortunately, when the comparison is made between copper(II) complexes in square-based pyramidal geometries and those in square planar environments (or a pseudo-octahedral) a little perturbed by an equatorial tetrahedral distortion, their redox potentials could fall in the same intermediate region. In this case spectroscopic data have to be handled with great care in order to have an answer about a copper complex geometrical characteristics.

  11. 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.

  12. In vitro study on the effect of doxycycline on the microbial activity of soil determined by redox-potential measuring system.

    PubMed

    Szakmár, Katalin; Reichart, Olivér; Szatmári, István; Erdősi, Orsolya; Szili, Zsuzsanna; László, Noémi; Székely Körmöczy, Péter; Laczay, Péter

    2014-09-01

    The potential effect of doxycycline on the microbial activity was investigated in three types of soil. Soil samples were spiked with doxycycline, incubated at 25°C and tested at 0, 2, 4 and 6 days after treatment. The microbiological activity of the soil was characterized by the viable count determined by plate pouring and by the time necessary to reach a defined rate of the redox-potential decrease termed as time to detection (TTD).The viable count of the samples was not changed during the storage. The TTD values, however exhibited a significant increase in the 0.2-1.6 mg/kg doxycycline concentration range compared to the untreated samples indicating concentration-dependent inhibitory effect on microbial activity. The potency of the effect was different in the 3 soil types. To describe the combined effect of the doxycycline concentration and time on the biological activity of one type of soil a mathematical model was constructed and applied.The change of microbial metabolic rate could be measured also without (detectable) change of microbial count when the traditional microbiological methods are not applicable. The applied new redox potential measurement-based method is a simple and useful procedure for the examination of microbial activity of soil and its potential inhibition by antibiotics.

  13. Effect of redox potential and pH status on degradation and adsorption behavior of tylosin in dairy lagoon sediment suspension.

    PubMed

    Ali, Muhammad; Wang, Jim J; DeLaune, Ronald D; Seo, Dong Cheol; Dodla, Syam K; Hernandez, Amy B

    2013-06-01

    Veterinary antibiotics are the most heavily used pharmaceuticals in intensive animal farming operation. Their presence in the environment through application of manure and lagoon water as fertilizer in agricultural fields has generated a growing concern in recent years due to potential threat to the ecosystem and the risk they pose to human and animal health. Among the antibiotics, tylosin, a macrolide class of antibiotics, has been widely used for disease prevention and growth promotion in swine, cattle/dairy, and poultry production. To understand degradation and sorption behavior of tylosin A, a laboratory microcosm incubation study was conducted on dairy lagoon sediments suspension under different pH (5.5, 7.0, 8.5) and redox potentials (Eh at -100 mV, 0 mV, +250 mV, +350 mV). Sorption and degradation of tylosin was strongly influenced by sediment pH and redox conditions. Under acidic (pH 5.5) and reduced (Eh -100 mV) condition, tylosin persisted in the solution phase of dairy lagoon sediment suspension much longer with resident time of 77 d. Under oxidized (Eh +350 mV) condition, microbial degradation was much greater causing 68-75% of tylosin loss from the solution at pH 5.5 and 32-75% at pH 7.0 during the 20 d incubation. At pH 8.5, abiotic transformation of tylosin A into unknown degradates rather than sediment adsorption and microbial degradation was the major mechanism controlling tylosin disappearance from the solution regardless of the status of redox potentials. Overall, the results suggested that under reduced condition with low pH, tylosin will be persisted in the lagoon effluents and residue of tylosin may enter agricultural fields through the application of lagoon slurry as fertilizer.

  14. Genistein decreases cellular redox potential, partially suppresses cell growth in HL‑60 leukemia cells and sensitizes cells to γ‑radiation‑induced cell death.

    PubMed

    Kim, In Gyu; Kim, Jin Sik; Lee, Jae Ha; Cho, Eun Wie

    2014-12-01

    Various mechanisms have been proposed to underlie the cellular activity of genistein, based on biological experiments and epidemiological studies. The present study demonstrated that genistein inhibited the expression of cytoplasmic nicotinamide adenine dinucleotide phosphate (NADP)‑dependent isocitrate dehydrogenase (cICDH), thus increasing levels of intracellular reactive oxygen species (ROS) in human promyeloid leukemia HL‑60 cells. In genistein‑treated cells, the cellular redox potential (GSH/GSSG) was significantly decreased. This decrease in redox potential was caused by significant downregulation of the cICDH gene, generating the reducing equivalents (NADPH) for maintenance of cellular redox potential and cellular ROS level, which may regulate cell growth and cell death. Genistein‑induced ROS partially induced rapid transition into the G2/M phase by upregulation of p21wap1/cip1 and apoptotic cell death. Treatment of cells with N‑acetylcysteine, a well‑known antioxidant (ROS scavenger), not only partially restored cell growth and inhibited cell cycle arrest in G2/M, but also prevented apoptotic cell death. By contrast, normal lymphocytes did not significantly progress into the G2/M phase and radiation‑induced cell death was inhibited by genistein treatment. Therefore, genistein and γ‑irradiation together synergistically cause cell death in leukemia cells, however, genistein has a radioprotective effect in normal human lymphocytes. In conclusion, it was suggested that genistein selectively functions, not as an antioxidant, but as a pro‑oxidant in HL‑60 cells. This property can increase ionizing radiation‑induced cell cycle arrest and sensitivity to apoptotic cell death in human promyeloid leukemia HL‑60 cells, but does not cause significant damage to normal cells.

  15. 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)

  16. Redox control of teratogenesis.

    PubMed

    Hansen, Jason M; Harris, Craig

    2013-01-01

    A number of human teratogens elicit their deleterious effects through mechanisms involving the generation of reactive oxygen species (ROS) and oxidative stress. However, classic definitions of oxidative stress do not fully coincide with basic fundamental principles of teratology. Newer definitions of oxidative stress focus on the targeted redox modification of cysteine/thiol functional groups found in the regulatory domains of critical signaling pathway proteins, suggesting that the targeted disruption of signaling through specific redox couples may account for the specificity of teratogen-induced malformations which previously could not be rationalized. Here, we review examples of teratogens that induce ROS and oxidative injury, describe oxidative stress-related teratogenic mechanisms, and provide rationale for developmental periods of sensitivity and species susceptibility. Understanding how chemicals disrupt redox status, induce oxidative stress leading to dysmorphogenesis becomes important to identify potential teratogens and develop therapeutic interventions for attenuation of harmful chemical effects in utero following exposure.

  17. Microprofiles of oxygen, redox potential, and pH, and microbial fermentation products in the highly alkaline gut of the saprophagous larva of Penthetria holosericea (Diptera: Bibionidae).

    PubMed

    Šustr, Vladimír; Stingl, Ulrich; Brune, Andreas

    2014-08-01

    The saprophagous larvae of bibionid flies harbor bacteria in their alkaline intestinal tracts, but little is known about the contribution of the gut microbiota to the digestion of their recalcitrant diet. In this study, we measured oxygen and hydrogen partial pressure, redox potential and pH in the midgut, gastric caeca and hindgut of larvae of the bibionid fly Penthetria holosericea with Clark-type O2 and H2 microsensors, platinum redox microelectrodes, and LIX-type pH microelectrodes. The center of the midgut lumen was anoxic, whereas gastric caeca and hindgut were hypoxic. However, redox potential profiles indicated oxidizing conditions throughout the gut, with lowest values in the midgut (+20 to +60mV). Hydrogen production was not detected. The midgut was extremely alkaline (pH around 11), whereas hindgut and gastric caeca were neutral to slightly alkaline. While HPLC analysis showed high concentrations of glucose in the midgut (15mM) and gastric caeca (27mM), the concentrations of microbial fermentation products such as lactate (2-4mM), acetate (<1mM) and succinate (<0.5mM) were low in all gut regions, suggesting that the contribution of microorganisms to the digestive process, particularly in the alkaline midgut, is only of minor importance. We conclude that the digestive strategy of the saprophytic larva of P. holosericea, which feeds selectively on decomposed leaves and its own microbe-rich faeces, differs fundamentally from those of detritivorous and humivorous insects, which host a highly active, fermentative microbiota in their alkaline midgut or hindgut compartments.

  18. Design, synthesis and evaluation of redox radiopharmaceuticals: a potential new approach for the development of brain imaging agents

    SciTech Connect

    Srivastava, P.C.; Knapp, F.F. Jr.

    1986-01-01

    The fabrication and complete evaluation are described of a dihydropyridine in equilibrium pyridinium salt type redox system for the delivery of radioiodinated agents to the brain. The pivotal intermediate, N-succinimidyl (1-methylpyridinium iodide)-3-carboxylate was prepared by condensation of nicotinic acid and N-hydroxysuccinimide in the presence of dicyclohexylcarbodimide, followed by quaternization of III with methyl iodide. Tissue distribution studies of /sup 125/I-labeled 4-iodoaniline and the redox agents were performed in rats. (/sup 125/I)Iodoaniline initially showed moderate (0.58% dose/gm) brain uptake with subsequent release of the radioactivity from the brain. (/sup 125/I)Iodoaniline, when coupled to a dihydropyridine carrier showed higher uptake and retention in the brain. The (/sup 125/I)iodophenylethyl analogue showed uptake and retention in the brain to be very similar. Apparently the lipophilic agents cross the blood-brain barrier and are oxidized (quaternized) within the brain. The blood-brain barrier then prevents their release resulting in high uptake and retention in the brain and high brain:blood ratios. 11 refs., 3 figs.

  19. Species dependence of the redox potential of the primary electron donor p700 in photosystem I of oxygenic photosynthetic organisms revealed by spectroelectrochemistry.

    PubMed

    Nakamura, Akimasa; Suzawa, Tomoyuki; Kato, Yuki; Watanabe, Tadashi

    2011-05-01

    The redox potential of the primary electron donor P700, E(m)(P700/P700(+)), of Photosystem I (PSI) has been determined for 10 oxygenic photosynthesis organisms, ranging from cyanobacteria, red algae, green algae to higher plants, by spectroelectrochemistry with an optically transparent thin-layer electrode (OTTLE) cell to elucidate the scattering by as much as 150 mV in reported values of E(m)(P700/P700(+)). The E(m)(P700/P700(+)) values determined within error ranges of ± 1-4 mV exhibited a significant species dependence, with a span >70 mV, from +398 to +470 mV vs. the standard hydrogen electrode (SHE). The E(m)(P700/P700(+)) value appears to change systematically in going from cyanobacteria and primitive eukaryotic red algae, then to green algae and higher plants. From an evolutionary point of view, this result suggests that the species believed to appear later in evolution of photosynthetic organisms exhibit higher values of E(m)(P700/P700(+)). Further, the species dependence of E(m)(P700/P700(+)) seems to originate in the species-dependent redox potentials of soluble metalloproteins, Cyt c(6) and plastocyanin, which re-reduce the oxidized P700 in the electron transfer chain.

  20. Redox probing study of the potential dependence of charge transport through Li2O2

    SciTech Connect

    Knudsen, Kristian B.; Luntz, Alan C.; Jensen, Søren H.; Vegge, Tejs; Hjelm, Johan

    2015-11-20

    In the field of energy storage devices the pursuit for cheap, high energy density, reliable secondary batteries is at the top of the agenda. The Li–O2 battery is one of the possible technologies that, in theory, should be able to close the gap, which exists between the present state-of-the-art Li-ion technologies and the demand placed on batteries by technologies such as electrical vehicles. Here we present a redox probing study of the charge transfer across the main deposition product lithium peroxide, Li2O2, in the Li–O2 battery using outer-sphere redox shuttles. The change in heterogeneous electron transfer exchange rate as a function of the potential and the Li2O2 layer thickness (~depth-of-discharge) was determined using electrochemical impedance spectroscopy. In addition, the attenuation of the electron transfer exchange rate with film thickness is dependent on the probing potential, providing evidence that hole transport is the dominant process for charge transfer through Li2O2 and showing that the origin of the sudden death observed upon discharge is due to charge transport limitations.

  1. Sexual Preferences in Nutrient Utilization Regulate Oxygen Consumption and Reactive Oxygen Species Generation in Schistosoma mansoni: Potential Implications for Parasite Redox Biology

    PubMed Central

    Oliveira, Matheus P.; Correa Soares, Juliana B. R.; Oliveira, Marcus F.

    2016-01-01

    Schistosoma mansoni, one of the causative agents of human schistosomiasis, has a unique antioxidant network that is key to parasite survival and a valuable chemotherapeutic target. The ability to detoxify and tolerate reactive oxygen species increases along S. mansoni development in the vertebrate host, suggesting that adult parasites are more exposed to redox challenges than young stages. Indeed, adult parasites are exposed to multiple redox insults generated from blood digestion, activated immune cells, and, potentially, from their own parasitic aerobic metabolism. However, it remains unknown how reactive oxygen species are produced by S. mansoni metabolism, as well as their biological effects on adult worms. Here, we assessed the contribution of nutrients and parasite gender to oxygen utilization pathways, and reactive oxygen species generation in whole unpaired adult S. mansoni worms. We also determined the susceptibilities of both parasite sexes to a pro-oxidant challenge. We observed that glutamine and serum importantly contribute to both respiratory and non-respiratory oxygen utilization in adult worms, but with different proportions among parasite sexes. Analyses of oxygen utilization pathways revealed that respiratory rates were high in male worms, which contrast with high non-respiratory rates in females, regardless nutritional sources. Interestingly, mitochondrial complex I-III activity was higher than complex IV specifically in females. We also observed sexual preferences in substrate utilization to sustain hydrogen peroxide production towards glucose in females, and glutamine in male worms. Despite strikingly high oxidant levels and hydrogen peroxide production rates, female worms were more resistant to a pro-oxidant challenge than male parasites. The data presented here indicate that sexual preferences in nutrient metabolism in adult S. mansoni worms regulate oxygen utilization and reactive oxygen species production, which may differently contribute

  2. Redox Properties of Free Radicals.

    ERIC Educational Resources Information Center

    Neta, P.

    1981-01-01

    Describes pulse radiolysis as a useful means in studing one-electron redox potentials. This method allows the production of radicals and the determination of their concentration and rates of reaction. (CS)

  3. Evaluation of the relative redox capacity of molybdenum-containing silicas obtained by molecular stratification

    SciTech Connect

    Bodyagin, B.O.; Olifirenko, V.V.; Pak, V.N.

    1989-02-01

    Redox titrations have been used to evaluate the redox properties of Mo-containing silicas obtained by molecular stratification. The Fe/sup 3+/-Fe/sup 2+/ pair has been chosen as the mediator. The changes in the content of Mo(V) and Mo(VI) in the surface layer over the course of the titration have been calculated for three series of samples. The curves obtained together with the values of the half-oxidation potentials attest to the significant dependencies of the redox properties on the degree of filling of the surface by modifying groupings.

  4. FtsZ inhibition and redox modulation with one chemical scaffold: Potential use of dihydroquinolines against mycobacteria.

    PubMed

    Duggirala, Sridevi; Napoleon, John Victor; Nankar, Rakesh P; Senu Adeeba, V; Manheri, Muraleedharan K; Doble, Mukesh

    2016-11-10

    The dual effect of FtsZ inhibition and oxidative stress by a group of 1,2-dihydroquinolines that culminate in bactericidal effect on mycobacterium strains is demonstrated. They inhibited the non-pathogenic Mycobacterium smegmatis mc(2) 155 with MIC as low as 0.9 μg/mL and induced filamentation. Detailed studies revealed their ability to inhibit polymerization and GTPase activity of MtbFtsZ (Mycobacterial filamentous temperature sensitive Z) with an IC50 value of ∼40 μM. In addition to such target specific effects, these compounds exerted a global cellular effect by causing redox-imbalance that was evident from overproduction of ROS in treated cells. Such multi-targeting effect with one chemical scaffold has considerable significance in this era of emerging drug resistance and could offer promise in the development of new therapeutic agents against tuberculosis.

  5. Redox properties of structural Fe in clay minerals: 3. Relationships between smectite redox and structural properties.

    PubMed

    Gorski, Christopher A; Klüpfel, Laura E; Voegelin, Andreas; Sander, Michael; Hofstetter, Thomas B

    2013-01-01

    Structural Fe in clay minerals is an important redox-active species in many pristine and contaminated environments as well as in engineered systems. Understanding the extent and kinetics of redox reactions involving Fe-bearing clay minerals has been challenging due to the inability to relate structural Fe(2+)/Fe(total) fractions to fundamental redox properties, such as reduction potentials (EH). Here, we overcame this challenge by using mediated electrochemical reduction (MER) and oxidation (MEO) to characterize the fraction of redox-active structural Fe (Fe(2+)/Fe(total)) in smectites over a wide range of applied EH-values (-0.6 V to +0.6 V). We examined Fe(2+)/Fe(total )- EH relationships of four natural Fe-bearing smectites (SWy-2, SWa-1, NAu-1, NAu-2) in their native, reduced, and reoxidized states and compared our measurements with spectroscopic observations and a suite of mineralogical properties. All smectites exhibited unique Fe(2+)/Fe(total) - EH relationships, were redox active over wide EH ranges, and underwent irreversible electron transfer induced structural changes that were observable with X-ray absorption spectroscopy. Variations among the smectite Fe(2+)/Fe(total) - EH relationships correlated well with both bulk and molecular-scale properties, including Fe(total) content, layer charge, and quadrupole splitting values, suggesting that multiple structural parameters determined the redox properties of smectites. The Fe(2+)/Fe(total) - EH relationships developed for these four commonly studied clay minerals may be applied to future studies interested in relating the extent of structural Fe reduction or oxidation to EH-values.

  6. Relationships between the effects of redox potential, alpha-thenoyltrifluoroacetone and malonate on O(2) and H2O2 generation by submitochondrial particles in the presence of succinate and antimycin.

    PubMed

    Ksenzenko, M; Konstantinov, A A; Khomutov, G B; Tikhonov, A N; Ruuge, E K

    1984-09-17

    The rate of the antimycin-induced H2O2 and O(2) generation in beef heart submitochondrial particles is maximal at the [succinate]/[fumarate] ratio of approximately 1:5 and decays at both higher and lower redox potentials. Succinate dehydrogenase inhibitors, such as TTFA or malonate, stimulate active oxygen production in the presence of excess succinate but are inhibitory at Eh values more positive than the optimal. The modulation of O(2) and H2O2 generation by these inhibitors can be explained by their effects on the steady-state redox potential(s) of the component(s) of mitochondrial site 2.

  7. Establishment of a Method for Measuring Antioxidant Capacity in Urine, Based on Oxidation Reduction Potential and Redox Couple I2/KI

    PubMed Central

    Cao, Tinghui; He, Min; Bai, Tianyu

    2016-01-01

    Objectives. To establish a new method for determination of antioxidant capacity of human urine based on the redox couple I2/KI and to evaluate the redox status of healthy and diseased individuals. Methods. The method was based on the linear relationship between oxidation reduction potential (ORP) and logarithm of concentration ratio of I2/KI. ORP of a solution with a known concentration ratio of I2/KI will change when reacted with urine. To determine the accuracy of the method, both vitamin C and urine were reacted separately with I2/KI solution. The new method was compared with the traditional method of iodine titration and then used to measure the antioxidant capacity of urine samples from 30 diabetic patients and 30 healthy subjects. Results. A linear relationship was found between logarithm of concentration ratio of I2/KI and ORP (R2 = 0.998). Both vitamin C and urine concentration showed a linear relationship with ORP (R2 = 0.994 and 0.986, resp.). The precision of the method was in the acceptable range and results of two methods had a linear correlation (R2 = 0.987). Differences in ORP values between diabetic group and control group were statistically significant (P < 0.05). Conclusions. A new method for measuring the antioxidant capacity of clinical urine has been established. PMID:28115919

  8. Wiring of the aldehyde oxidoreductase PaoABC to electrode surfaces via entrapment in low potential phenothiazine-modified redox polymers.

    PubMed

    Pinyou, Piyanut; Ruff, Adrian; Pöller, Sascha; Alsaoub, Sabine; Leimkühler, Silke; Wollenberger, Ulla; Schuhmann, Wolfgang

    2016-06-01

    Phenothiazine-modified redox hydrogels were synthesized and used for the wiring of the aldehyde oxidoreductase PaoABC to electrode surfaces. The effects of the pH value and electrode surface modification on the biocatalytic activity of the layers were studied in the presence of vanillin as the substrate. The enzyme electrodes were successfully employed as bioanodes in vanillin/O2 biofuel cells in combination with a high potential bilirubin oxidase biocathode. Open circuit voltages of around 700 mV could be obtained in a two compartment biofuel cell setup. Moreover, the use of a rather hydrophobic polymer with a high degree of crosslinking sites ensures the formation of stable polymer/enzyme films which were successfully used as bioanode in membrane-less biofuel cells.

  9. Redox Control of Cardiac Excitability

    PubMed Central

    Aggarwal, Nitin T.

    2013-01-01

    Abstract Reactive oxygen species (ROS) have been associated with various human diseases, and considerable attention has been paid to investigate their physiological effects. Various ROS are synthesized in the mitochondria and accumulate in the cytoplasm if the cellular antioxidant defense mechanism fails. The critical balance of this ROS synthesis and antioxidant defense systems is termed the redox system of the cell. Various cardiovascular diseases have also been affected by redox to different degrees. ROS have been indicated as both detrimental and protective, via different cellular pathways, for cardiac myocyte functions, electrophysiology, and pharmacology. Mostly, the ROS functions depend on the type and amount of ROS synthesized. While the literature clearly indicates ROS effects on cardiac contractility, their effects on cardiac excitability are relatively under appreciated. Cardiac excitability depends on the functions of various cardiac sarcolemal or mitochondrial ion channels carrying various depolarizing or repolarizing currents that also maintain cellular ionic homeostasis. ROS alter the functions of these ion channels to various degrees to determine excitability by affecting the cellular resting potential and the morphology of the cardiac action potential. Thus, redox balance regulates cardiac excitability, and under pathological regulation, may alter action potential propagation to cause arrhythmia. Understanding how redox affects cellular excitability may lead to potential prophylaxis or treatment for various arrhythmias. This review will focus on the studies of redox and cardiac excitation. Antioxid. Redox Signal. 18, 432–468. PMID:22897788

  10. Selective activation of mitomycin A by thiols to form DNA cross-links and monoadducts: biochemical basis for the modulation of mitomycin cytotoxicity by the quinone redox potential.

    PubMed

    Paz, M M; Das, A; Palom, Y; He, Q Y; Tomasz, M

    2001-08-16

    Mitomycin A (MA) but not mitomycin C (MC) cross-linked linearized (32)P-pBR322 DNA in the presence of dithiothreitol (DTT) or glutathione (GSH), as shown by a sensitive DNA cross-link assay. Incubation of calf-thymus DNA with MA and DTT or mercaptoethanol (MER) resulted in the formation of MA-DNA adducts, which were isolated from nuclease digests of the drug-DNA complexes by HPLC. The adducts were characterized by their UV absorption spectra, electrospray ionization mass spectrometry (ESIMS), and facile conversion from 7-methoxy- to 7-amino-substituted mitosene type adducts upon 10% NH(4)OH treatment, which were identical with known adducts of MC. Both DNA interstrand and intrastrand cross-link adducts, linking two deoxyguanosine residues at N(2), as well as several deoxyguanosine-N(2) monoadducts of MA, were identified. No DNA adducts were formed with MC under the same conditions. A specificity of DNA cross-link formation for the CpG sequence was observed using 12-mer synthetic oligodeoxyribonucleotides as substrates and as DNA sequence models, in analogy to the known CpG sequence specificity of MC-induced DNA cross-links. MA is known to be more cytotoxic by 2-3 orders of magnitude than MC, and this property correlates with redox potentials of MA (-0.19 V) and MA analogues that are higher than those of MC (-0.40 V) and its analogues. It is suggested that the biochemical basis for the higher cytotoxic potency of MA is MA's propensity to be reductively activated by cellular thiols while MC is resistant to thiol activation. This distinction is probably derived from the large difference between the quinone redox potentials of the two drugs.

  11. The role of heme propionate in controlling the redox potential of heme: square wave voltammetry of protoporphyrinato IX iron (III) in aqueous surfactant micelles.

    PubMed

    Das, D K; Medhi, O K

    1998-05-01

    The proton equilibrium in aqueous surfactant solutions of hemin, (PPIX)Fe(H2O)+2, involving the propionic acid groups is reported (PPIX = protoporphyrinato IX). The surfactant used are sodium dodecyl sulphate (SDS), triton X-100 (TX-100) and hexadecyl trimethylammonium bromide (CTAB). The pKa values, determined spectroscopically from the pH variations of the Soret absorption, are found at ca. 3.5 in SDS and TX-100 micelles. In the cationic surfactant (CTAB) the absorbance of hemin is independent of the hydrogen ion concentration in solution and this surfactant form a salt-link with the heme propionate group. The dependence of mid-point potential on pH indicates that the heme propionate undergoes a redox-linked changed in pKa from 3.2-3.5 in the ferric form to 4.4-4.5 in the ferrous form (27 degrees C, mu = 0.2 M). The change in the mid-point potential per unit change in pH. delta E/delta pH, is ca. -59 mV. Replacement of the water molecules in hemin by tetrahydrofuran, (PPIX)Fe(thf)+2, induces a considerable shift of pKa of the heme propionate: 6.2-6.8 in the ferric form and 7.5-7.8 in the ferrous form. The lower value of pKa in diaquo hemin is attributed to stabilisation of the propionate by a hydrogen bond with coordinated water molecules. All these results may be interpreted in terms of the involvement of a heme propionate group in redox linked uptake of protons and the influence of hydrogen bonding and salt-link formation on the pKa of the proton equilibrium.

  12. In situ measurements of dissolved oxygen, pH and redox potential of biocathode microenvironments using microelectrodes.

    PubMed

    Wang, Zejie; Deng, Huan; Chen, Lihui; Xiao, Yong; Zhao, Feng

    2013-03-01

    Biofilms are the core component of bioelectrochemical systems (BESs). To understand the polarization effects on biocathode performance of BES, dissolved oxygen concentrations, pHs and oxidation-reduction potentials of biofilm microenvironments were determined in situ. The results showed that lower polarization potentials resulted in the generation of larger currents and higher pH values, as well as the consumption of more oxygen. Oxidation-reduction potentials of biofilms were mainly affected by polarization potentials of the electrode rather than the concentration of dissolved oxygen or pH value, and its changes in the potentials corresponded to the electric field distribution of the electrode surface. The results demonstrated that a sufficient supply of dissolved oxygen and pH control of the biocathode are necessary to obtain optimal performance of BESs; a lower polarization potential endowed microorganisms with a higher electrochemical activity.

  13. A New Hybrid Redox Flow Battery with Multiple Redox Couples

    SciTech Connect

    Wang, Wei; Li, Liyu; Nie, Zimin; Chen, Baowei; Luo, Qingtao; Shao, Yuyan; Wei, Xiaoliang; Chen, Feng; Xia, Guanguang; Yang, Zhenguo

    2012-05-19

    A redox flow battery using V{sup 4+}/V{sup 5+} vs. V{sup 2+}/V{sup 3+} and Fe{sup 2+}/Fe{sup 3+} vs. V{sup 2+}/V{sup 3+} redox couples in chloric/sulphuric mixed acid supporting electrolyte was investigated for potential stationary energy storage applications. The Fe/V hybrid redox flow cell using mixed reactant solutions operated within a voltage window of 0.5-1.7 V demonstrated stable cycling over 100 cycles with energy efficiency {approx}80% and no capacity fading at room temperature. A 66% improvement in the energy density of the Fe/V hybrid cell was achieved compared with the previous reported Fe/V cell using only Fe{sup 2+}/Fe{sup 3+} vs. V{sup 2+}/V{sup 3+} redox couples.

  14. Non-equilibrium thermodynamics of thiol/disulfide redox systems: A perspective on redox systems biology

    PubMed Central

    Kemp, Melissa; Go, Young-Mi; Jones, Dean P.

    2008-01-01

    Understanding the dynamics of redox elements in biologic systems remains a major challenge for redox signaling and oxidative stress research. Central redox elements include evolutionarily conserved subsets of cysteines and methionines of proteins which function as sulfur switches and labile reactive oxygen species (ROS) and reactive nitrogen species (RNS) which function in redox signaling. The sulfur switches depend upon redox environments in which rates of oxidation are balanced with rates of reduction through the thioredoxins, glutathione/glutathione disulfide and cysteine/cystine redox couples. These central couples, which we term redox control nodes, are maintained at stable but non-equilibrium steady states, are largely independently regulated in different subcellular compartments and are quasi-independent from each other within compartments. Disruption of the redox control nodes can differentially affect sulfur switches, thereby creating a diversity of oxidative stress responses. Systems biology provides approaches to address the complexity of these responses. In the present review, we summarize thiol/disulfide pathway, redox potential and rate information as a basis for kinetic modeling of sulfur switches. The summary identifies gaps in knowledge especially related to redox communication between compartments, definition of redox pathways and discrimination between types of sulfur switches. A formulation for kinetic modeling of GSH/GSSG redox control indicates that systems biology could encourage novel therapeutic approaches to protect against oxidative stress by identifying specific redox-sensitive sites which could be targeted for intervention. PMID:18155672

  15. Biochemical characterization of laccase from hairy root culture of Brassica juncea L. and role of redox mediators to enhance its potential for the decolorization of textile dyes.

    PubMed

    Telke, Amar A; Kagalkar, Anuradha N; Jagtap, Umesh B; Desai, Neetin S; Bapat, Vishwas A; Govindwar, Sanjay P

    2011-12-01

    In vitro transgenic hairy root cultures provide a rapid system for physiological, biochemical studies and screening of plants for their phytoremediation potential. The hairy root cultures of Brassica juncea L. showed 92% decolorization of Methyl orange within 4 days. Out of the different redox mediators that were used to achieve enhanced decolorization, 2, 2'-Azinobis, 3-ethylbenzothiazoline-6-sulfonic acid (ABTS) was found to be the most efficient. Laccase activity of 4.5 U mg(-1) of protein was observed in hairy root cultures of Brassica juncea L., after the decolorization of Methyl orange. Intracellular laccase produced by B. juncea root cultures grown in MS basal medium was purified up to 2.0 fold with 6.62 U mg(-1) specific activity using anion-exchange chromatography. Molecular weight of the purified laccase was estimated to be 148 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The purified enzyme efficiently oxidized ABTS which was also required for oxidation of the other tested substrates. The pH and temperature optimum for laccase activity were 4.0 and 40°C, respectively. The purified enzyme was stable up to 50°C and was stable in the pH range of 4.0-6.0. Laccase activity was strongly inhibited by sodium azide, EDTA, dithiothreitol and L: -cysteine. The purified enzyme decolorized various textile dyes in the presence of ABTS as an efficient redox mediator. These findings contribute to a better understanding of the enzymatic process involved in phytoremediation of textile dyes by using hairy roots.

  16. 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

  17. Voltammetric characterization of the aerobic energy-dissipating nitrate reductase of Paracoccus pantotrophus: exploring the activity of a redox-balancing enzyme as a function of electrochemical potential.

    PubMed

    Gates, Andrew J; Richardson, David J; Butt, Julea N

    2008-01-01

    Paracoccus pantotrophus expresses two nitrate reductases associated with respiratory electron transport, termed NapABC and NarGHI. Both enzymes derive electrons from ubiquinol to reduce nitrate to nitrite. However, while NarGHI harnesses the energy of the quinol/nitrate couple to generate a transmembrane proton gradient, NapABC dissipates the energy associated with these reducing equivalents. In the present paper we explore the nitrate reductase activity of purified NapAB as a function of electrochemical potential, substrate concentration and pH using protein film voltammetry. Nitrate reduction by NapAB is shown to occur at potentials below approx. 0.1 V at pH 7. These are lower potentials than required for NarGH nitrate reduction. The potentials required for Nap nitrate reduction are also likely to require ubiquinol/ubiquinone ratios higher than are needed to activate the H(+)-pumping oxidases expressed during aerobic growth where Nap levels are maximal. Thus the operational potentials of P. pantotrophus NapAB are consistent with a productive role in redox balancing. A Michaelis constant (K(M)) of approx. 45 muM was determined for NapAB nitrate reduction at pH 7. This is in line with studies on intact cells where nitrate reduction by Nap was described by a Monod constant (K(S)) of less than 15 muM. The voltammetric studies also disclosed maximal NapAB activity in a narrow window of potential. This behaviour is resistant to change of pH, nitrate concentration and inhibitor concentration and its possible mechanistic origins are discussed.

  18. A point mutation in atpC1 raises the redox potential of the Arabidopsis chloroplast ATP synthase gamma-subunit regulatory disulfide above the range of thioredoxin modulation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The light-dependent regulation of chloroplast ATP synthase activity depends on an intricate but ill-defined interplay between the proton electrochemical potential across the thylakoid membrane and thioredoxin-mediated redox modulation of a cysteine bridge located on the ATP synthase gamma-subunit. T...

  19. Influence of oxygen content of the certain types of biodiesels on particulate oxidative potential.

    PubMed

    Hedayat, F; Stevanovic, S; Milic, A; Miljevic, B; Nabi, M N; Zare, A; Bottle, S E; Brown, R J; Ristovski, Z D

    2016-03-01

    Oxidative potential (OP) is related to the organic phase, specifically to its oxygenated organic fraction (OOA). Furthermore, the oxygen content of fuel molecules has significant influence on particulate OP. Thus, this study aimed to explore the actual dependency of the OOA and ROS to the oxygen content of the fuel. In order to reach the goal, different biodiesels blends, with various ranges of oxygen content; have been employed. The compact time of flight aerosol mass spectrometer (c-ToF AMS) enabled better identification of OOA. ROS monitored by using two assays: DTT and BPEA-nit. Despite emitting lower mass, both assays agreed that oxygen content of a biodiesel is directly correlated with its OOA, and highly related to its OP. Hence, the more oxygen included in the considered biodiesels, the higher the OP of PM emissions. This highlights the importance of taking oxygen content into account while assessing emissions from new fuel types, which is relevant from a health effects standpoint.

  20. Changes in intracellular and apoplastic peroxidase activity, ascorbate redox status, and root elongation induced by enhanced ascorbate content in Allium cepa L.

    PubMed

    Córdoba-Pedregosa, María del Carmen; Villalba, José Manuel; Córdoba, Francisco; González-Reyes, José Antonio

    2005-02-01

    Onions (Allium cepa L.) treated with external ascorbic acid or with the immediate precursor of its synthesis L-galactono-gamma-lactone show a stimulated elongation rate of the roots and an increase in the number of new radicles appearing at the bulb base. Treatment with both molecules resulted in an enhanced accumulation of ascorbate and dehydroascorbate along the root axis, but the distribution of these redox forms was not uniform along the root, as detected in intracellular (symplastic) and extracellular (apoplastic) compartments. Thus, those radicular zones metabolically more active, such as the meristem and the elongation zone, accumulated the highest amount of both redox forms of ascorbate. On the other hand, ascorbate and L-galactono-gamma-lactone also stimulated cytosolic glucose-6-phosphate dehydrogenase activity and inhibited peroxidase activity as deduced from in vivo and in vitro experiments. Differences were also found when comparing apoplastic and symplastic activities. These results are compatible with the idea of an ascorbate-mediated stimulation of root growth by inhibiting cell wall stiffening and increasing root metabolism.

  1. Accurate calculation of absolute one-electron redox potentials of some para-quinone derivatives in acetonitrile.

    PubMed

    Namazian, Mansoor; Coote, Michelle L

    2007-08-02

    Standard ab initio molecular orbital theory and density functional theory calculations have been used to calculate absolute one-electron reduction potentials of several para-quinones in acetonitrile. The high-level composite method of G3(MP2)-RAD is used for the gas-phase calculations and a continuum model of solvation, CPCM, has been employed to calculate solvation energies. To compare the theoretical reduction potentials with experiment, the reduction potentials relative to a standard calomel electrode (SCE) have also been calculated and compared to experimental values. The average error of the calculated reduction potentials using the proposed method is 0.07 V without any additional approximation. An ONIOM method in which the core is studied at G3(MP2)-RAD and the substituent effect of the rest of the molecule is studied at R(O)MP2/6-311+G(3df,2p) provides an accurate low-cost alternative to G3(MP2)-RAD for larger molecules.

  2. Prediction of water content at different potentials from soil property data in Jazan region

    NASA Astrophysics Data System (ADS)

    Alturki, Ali; Ibrahim, Hesham

    2016-04-01

    In dry regions effective irrigation management is crucial to maintain crop production and sustain limited water resources. Effective irrigation requires good knowledge of soil water content in the root zone. However, measurement of soil water in the root zone over time is extremely expensive and time consuming. On the other hand, weather and basic soil property data are more available, either from existing databases or by direct measurement in the field. Simulation models can be used to efficiently and accurately estimate soil water content and subsequent irrigation requirements based on the available weather and soil data. In this study we investigated three hierarchical approaches to predict water content at variable potentials (0, 10, 33, 60, 100, 300, 500, 800, 1000, and 1500 kPa) using the Rosetta model: soil texture class (STC); percent of sand, silt, and clay (SSC); bulk density, percent of sand, silt, and clay, and water content measurements at 33 and 1500 kPa (SSC+WC). Estimation of soil water content at 43 locations in Jazan region using the three hierarchical approaches was compared with gravimetric water content. Results showed that the three approaches failed to describe water content accurately at saturation conditions (<10kPa). At water potentials lower than 10 kPa, good agreement was obtained, in general, between measured and simulated soil water content indicating that soil property data can be used to provide adequate estimates of the average soil water content in the root zone. The third approach gave the best results as indicated by an average NSCE value of 0.75 as compared to 0.16 and 0.18 for the first and second approaches, respectively. The ability to predict the amount of available water in the soil profile will facilitate the accurate estimate of irrigation requirements and achieve effective irrigation scheduling especially in locations where only limited weather and soil date are available.

  3. Performance evaluation of TDT soil water content and watermark soil water potential sensors

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study evaluated the performance of digitized Time Domain Transmissometry (TDT) soil water content sensors (Acclima, Inc., Meridian, ID) and resistance-based soil water potential sensors (Watermark 200, Irrometer Company, Inc., Riverside, CA) in two soils. The evaluation was performed by compar...

  4. Factors Controlling Redox Speciation of Plutonium and Neptunium in Extraction Separation Processes

    SciTech Connect

    Paulenova, Alena; Vandegrift, III, George F.

    2013-09-24

    The objective of the project was to examine the factors controlling redox speciation of plutonium and neptunium in UREX+ extraction in terms of redox potentials, redox mechanism, kinetics and thermodynamics. Researchers employed redox-speciation extractions schemes in parallel to the spectroscopic experiments. The resulting distribution of redox species w studied uring spectroscopic, electrochemical, and spectro-electrochemical methods. This work reulted in collection of data on redox stability and distribution of redox couples in the nitric acid/nitrate electrolyte and the development of redox buffers to stabilize the desired oxidation state of separated radionuclides. The effects of temperature and concentrations on the redox behavior of neptunium were evaluated.

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

    PubMed

    Trivedi, Malav S; Deth, Richard

    2014-01-01

    Alcohol and other drugs of abuse, including psychostimulants and opioids, can induce epigenetic changes: a contributing factor for drug addiction, tolerance, and associated withdrawal symptoms. DNA methylation is a major epigenetic mechanism and it is one of more than 200 methylation reactions supported by methyl donor S-adenosylmethionine (SAM). Levels of SAM are controlled by cellular redox status via the folate and vitamin B12-dependent enzyme methionine synthase (MS). For example, under oxidative conditions MS is inhibited, diverting its substrate homocysteine (HCY) to the trans sulfuration pathway. Alcohol, dopamine, and morphine, can alter intracellular levels of glutathione (GSH)-based cellular redox status, subsequently affecting SAM levels and DNA methylation status. Here, existing evidence is presented in a coherent manner to propose a novel hypothesis implicating the involvement of redox-based epigenetic changes in drug addiction. Further, we discuss how a "gene priming" phenomenon can contribute to the maintenance of redox and methylation status homeostasis under various stimuli including drugs of abuse. Additionally, a new mechanistic rationale for the use of metabolic interventions/redox-replenishers as symptomatic treatment of alcohol and other drug addiction and associated withdrawal symptoms is also provided. Hence, the current review article strengthens the hypothesis that neuronal metabolism has a critical bidirectional coupling with epigenetic changes in drug addiction exemplified by the link between redox-based metabolic changes and resultant epigenetic consequences under the effect of drugs of abuse.

  6. Redox subpopulations and the risk of cancer progression: a new method for characterizing redox heterogeneity

    NASA Astrophysics Data System (ADS)

    Xu, He N.; Li, Lin Z.

    2016-02-01

    It has been shown that a malignant tumor is akin to a complex organ comprising of various cell populations including tumor cells that are genetically, metabolically and functionally different. Our redox imaging data have demonstrated intra-tumor redox heterogeneity in all mouse xenografts derived from human melanomas, breast, prostate, and colon cancers. Based on the signals of NADH and oxidized flavoproteins (Fp, including flavin adenine dinucleotide (FAD)) and their ratio, i.e., the redox ratio, which is an indicator of mitochondrial metabolic status, we have discovered several distinct redox subpopulations in xenografts of breast tumors potentially recapitulating functional/metabolic heterogeneity within the tumor. Furthermore, xenografts of breast tumors with higher metastatic potential tend to have a redox subpopulation whose redox ratio is significantly different from that of tumors with lower metastatic potential and usually have a bi-modal distribution of the redox ratio. The redox subpopulations from human breast cancer samples can also be very complex with multiple subpopulations as determined by fitting the redox ratio histograms with multi- Gaussian functions. In this report, we present a new method for identifying the redox subpopulations within individual breast tumor xenografts and human breast tissues, which may be used to differentiate between breast cancer and normal tissue and among breast cancer with different risks of progression.

  7. Porous media matric potential and water content measurements during parabolic flight.

    PubMed

    Norikane, Joey H; Jones, Scott B; Steinberg, Susan L; Levine, Howard G; Or, Dani

    2005-01-01

    Control of water and air in the root zone of plants remains a challenge in the microgravity environment of space. Due to limited flight opportunities, research aimed at resolving microgravity porous media fluid dynamics must often be conducted on Earth. The NASA KC-135 reduced gravity flight program offers an opportunity for Earth-based researchers to study physical processes in a variable gravity environment. The objectives of this study were to obtain measurements of water content and matric potential during the parabolic profile flown by the KC-135 aircraft. The flight profile provided 20-25 s of microgravity at the top of the parabola, while pulling 1.8 g at the bottom. The soil moisture sensors (Temperature and Moisture Acquisition System: Orbital Technologies, Madison, WI) used a heat-pulse method to indirectly estimate water content from heat dissipation. Tensiometers were constructed using a stainless steel porous cup with a pressure transducer and were used to measure the matric potential of the medium. The two types of sensors were placed at different depths in a substrate compartment filled with 1-2 mm Turface (calcined clay). The ability of the heat-pulse sensors to monitor overall changes in water content in the substrate compartment decreased with water content. Differences in measured water content data recorded at 0, 1, and 1.8 g were not significant. Tensiometer readings tracked pressure differences due to the hydrostatic force changes with variable gravity. The readings may have been affected by changes in cabin air pressure that occurred during each parabola. Tensiometer porous membrane conductivity (function of pore size) and fluid volume both influence response time. Porous media sample height and water content influence time-to-equilibrium, where shorter samples and higher water content achieve faster equilibrium. Further testing is needed to develop these sensors for space flight applications.

  8. Porous media matric potential and water content measurements during parabolic flight

    NASA Technical Reports Server (NTRS)

    Norikane, Joey H.; Jones, Scott B.; Steinberg, Susan L.; Levine, Howard G.; Or, Dani

    2005-01-01

    Control of water and air in the root zone of plants remains a challenge in the microgravity environment of space. Due to limited flight opportunities, research aimed at resolving microgravity porous media fluid dynamics must often be conducted on Earth. The NASA KC-135 reduced gravity flight program offers an opportunity for Earth-based researchers to study physical processes in a variable gravity environment. The objectives of this study were to obtain measurements of water content and matric potential during the parabolic profile flown by the KC-135 aircraft. The flight profile provided 20-25 s of microgravity at the top of the parabola, while pulling 1.8 g at the bottom. The soil moisture sensors (Temperature and Moisture Acquisition System: Orbital Technologies, Madison, WI) used a heat-pulse method to indirectly estimate water content from heat dissipation. Tensiometers were constructed using a stainless steel porous cup with a pressure transducer and were used to measure the matric potential of the medium. The two types of sensors were placed at different depths in a substrate compartment filled with 1-2 mm Turface (calcined clay). The ability of the heat-pulse sensors to monitor overall changes in water content in the substrate compartment decreased with water content. Differences in measured water content data recorded at 0, 1, and 1.8 g were not significant. Tensiometer readings tracked pressure differences due to the hydrostatic force changes with variable gravity. The readings may have been affected by changes in cabin air pressure that occurred during each parabola. Tensiometer porous membrane conductivity (function of pore size) and fluid volume both influence response time. Porous media sample height and water content influence time-to-equilibrium, where shorter samples and higher water content achieve faster equilibrium. Further testing is needed to develop these sensors for space flight applications.

  9. Pseudoazurin from Sinorhizobium meliloti as an electron donor to copper-containing nitrite reductase: influence of the redox partner on the reduction potentials of the enzyme copper centers.

    PubMed

    Ferroni, Félix M; Marangon, Jacopo; Neuman, Nicolás I; Cristaldi, Julio C; Brambilla, Silvina M; Guerrero, Sergio A; Rivas, María G; Rizzi, Alberto C; Brondino, Carlos D

    2014-08-01

    Pseudoazurin (Paz) is the physiological electron donor to copper-containing nitrite reductase (Nir), which catalyzes the reduction of NO2 (-) to NO. The Nir reaction mechanism involves the reduction of the type 1 (T1) copper electron transfer center by the external physiological electron donor, intramolecular electron transfer from the T1 copper center to the T2 copper center, and nitrite reduction at the type 2 (T2) copper catalytic center. We report the cloning, expression, and characterization of Paz from Sinorhizobium meliloti 2011 (SmPaz), the ability of SmPaz to act as an electron donor partner of S. meliloti 2011 Nir (SmNir), and the redox properties of the metal centers involved in the electron transfer chain. Gel filtration chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis together with UV-vis and EPR spectroscopies revealed that as-purified SmPaz is a mononuclear copper-containing protein that has a T1 copper site in a highly distorted tetrahedral geometry. The SmPaz/SmNir interaction investigated electrochemically showed that SmPaz serves as an efficient electron donor to SmNir. The formal reduction potentials of the T1 copper center in SmPaz and the T1 and T2 copper centers in SmNir, evaluated by cyclic voltammetry and by UV-vis- and EPR-mediated potentiometric titrations, are against an efficient Paz T1 center to Nir T1 center to Nir T2 center electron transfer. EPR experiments proved that as a result of the SmPaz/SmNir interaction in the presence of nitrite, the order of the reduction potentials of SmNir reversed, in line with T1 center to T2 center electron transfer being thermodynamically more favorable.

  10. Event-related potentials in response to violations of content and temporal event knowledge.

    PubMed

    Drummer, Janna; van der Meer, Elke; Schaadt, Gesa

    2016-01-08

    Scripts that store knowledge of everyday events are fundamentally important for managing daily routines. Content event knowledge (i.e., knowledge about which events belong to a script) and temporal event knowledge (i.e., knowledge about the chronological order of events in a script) constitute qualitatively different forms of knowledge. However, there is limited information about each distinct process and the time course involved in accessing content and temporal event knowledge. Therefore, we analyzed event-related potentials (ERPs) in response to either correctly presented event sequences or event sequences that contained a content or temporal error. We found an N400, which was followed by a posteriorly distributed P600 in response to content errors in event sequences. By contrast, we did not find an N400 but an anteriorly distributed P600 in response to temporal errors in event sequences. Thus, the N400 seems to be elicited as a response to a general mismatch between an event and the established event model. We assume that the expectancy violation of content event knowledge, as indicated by the N400, induces the collapse of the established event model, a process indicated by the posterior P600. The expectancy violation of temporal event knowledge is assumed to induce an attempt to reorganize the event model in working memory, a process indicated by the frontal P600.

  11. Control of high level radioactive waste-glass melters. Part 5, Modelling of complex redox effects

    SciTech Connect

    Bickford, D.F.; Choi, A.S.

    1991-12-31

    Slurry Fed Melters (SFM) are being developed in the United States, Europe and Japan for the conversion of high-level radioactive waste to borosilicate glass for permanent disposal. The high transition metal, noble metal, nitrate, organic, and sulfate contents of these wastes lead to unique melter redox control requirements. Pilot waste-glass melter operations have indicated the possibility of nickel sulfide or noble-metal fission-product accumulation on melter floors, which can lead to distortion of electric heating patterns, and decrease melter life. Sulfide formation is prevented by control of the redox chemistry of the melter feed. The redox state of waste-glass melters is determined by balance between the reducing potential of organic compounds in the feed, and the oxidizing potential of gases above the melt, and nitrates and polyvalent elements in the waste. Semiquantitative models predicting limitations of organic content have been developed based on crucible testing. Computerized thermodynamic computations are being developed to predict the sequence and products of redox reactions and is assessing process variations. Continuous melter test results have been compared to improved computer staged-thermodynamic-models of redox behavior. Feed chemistry control to prevent sulfide and moderate noble metal accumulations are discussed. 17 refs., 3 figs.

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

    PubMed

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

    2008-01-01

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

  13. The N-terminal sequence of the extrinsic PsbP protein modulates the redox potential of Cyt b559 in photosystem II

    PubMed Central

    Nishimura, Taishi; Nagao, Ryo; Noguchi, Takumi; Nield, Jon; Sato, Fumihiko; Ifuku, Kentaro

    2016-01-01

    The PsbP protein, an extrinsic subunit of photosystem II (PSII) in green plants, is known to induce a conformational change around the catalytic Mn4CaO5 cluster securing the binding of Ca2+ and Cl– in PSII. PsbP has multiple interactions with the membrane subunits of PSII, but how these affect the structure and function of PSII requires clarification. Here, we focus on the interactions between the N-terminal residues of PsbP and the α subunit of Cytochrome (Cyt) b559 (PsbE). A key observation was that a peptide fragment formed of the first N-terminal 15 residues of PsbP, ‘pN15’, was able to convert Cyt b559 into its HP form. Interestingly, addition of pN15 to NaCl-washed PSII membranes decreased PSII’s oxygen-evolving activity, even in the presence of saturating Ca2+ and Cl– ions. In fact, pN15 reversibly inhibited the S1 to S2 transition of the OEC in PSII. These data suggest that pN15 can modulate the redox property of Cyt b559 involved in the side-electron pathway in PSII. This potential change of Cyt b559, in the absence of the C-terminal domain of PsbP, however, would interfere with any electron donation from the Mn4CaO5 cluster, leading to the possibility that multiple interactions of PsbP, binding to PSII, have distinct roles in regulating electron transfer within PSII. PMID:26887804

  14. Tetrodotoxin blockade on canine cardiac L-type Ca²⁺ channels depends on pH and redox potential.

    PubMed

    Hegyi, Bence; Komáromi, István; Kistamás, Kornél; Ruzsnavszky, Ferenc; Váczi, Krisztina; Horváth, Balázs; Magyar, János; Bányász, Tamás; Nánási, Péter P; Szentandrássy, Norbert

    2013-06-14

    Tetrodotoxin (TTX) is believed to be one of the most selective inhibitors of voltage-gated fast Na⁺ channels in excitable tissues. Recently, however, TTX has been shown to block L-type Ca²⁺ current (I(Ca)) in canine cardiac cells. In the present study, the TTX-sensitivity of I(Ca) was studied in isolated canine ventricular myocytes as a function of (1) channel phosphorylation, (2) extracellular pH and (3) the redox potential of the bathing medium using the whole cell voltage clamp technique. Fifty-five micromoles of TTX (IC₅₀ value obtained under physiological conditions) caused 60% ± 2% inhibition of I(Ca) in acidic (pH = 6.4), while only a 26% ± 2% block in alkaline (pH = 8.4) milieu. Similarly, the same concentration of TTX induced 62% ± 6% suppression of ICa in a reductant milieu (containing glutathione + ascorbic acid + dithiothreitol, 1 mM each), in contrast to the 31% ± 3% blockade obtained in the presence of a strong oxidant (100 μM H₂O₂). Phosphorylation of the channel protein (induced by 3 μM forskolin) failed to modify the inhibiting potency of TTX; an IC₅₀ value of 50 ± 4 μM was found in forskolin. The results are in a good accordance with the predictions of our model, indicating that TTX binds, in fact, to the selectivity filter of cardiac L-type Ca channels.

  15. Redox state and energy metabolism during liver regeneration: alterations produced by acute ethanol administration.

    PubMed

    Gutiérrez-Salinas, J; Miranda-Garduño, L; Trejo-Izquierdo, E; Díaz-Muñoz, M; Vidrio, S; Morales-González, J A; Hernández-Muñoz, R

    1999-12-01

    Ethanol metabolism can induce modifications in liver metabolic pathways that are tightly regulated through the availability of cellular energy and through the redox state. Since partial hepatectomy (PH)-induced liver proliferation requires an oversupply of energy for enhanced syntheses of DNA and proteins, the present study was aimed at evaluating the effect of acute ethanol administration on the PH-induced changes in cellular redox and energy potentials. Ethanol (5 g/kg body weight) was administered to control rats and to two-thirds hepatectomized rats. Quantitation of the liver content of lactate, pyruvate, beta-hydroxybutyrate, acetoacetate, and adenine nucleotides led us to estimate the cytosolic and mitochondrial redox potentials and energy parameters. Specific activities in the liver of alcohol-metabolizing enzymes also were measured in these animals. Liver regeneration had no effect on cellular energy availability, but induced a more reduced cytosolic redox state accompanied by an oxidized mitochondrial redox state during the first 48 hr of treatment; the redox state normalized thereafter. Administration of ethanol did not modify energy parameters in PH rats, but this hepatotoxin readily blocked the PH-induced changes in the cellular redox state. In addition, proliferating liver promoted decreases in the activity of alcohol dehydrogenase (ADH) and of cytochrome P4502E1 (CYP2E1); ethanol treatment prevented the PH-induced diminution of ADH activity. In summary, our data suggest that ethanol could minimize the PH-promoted metabolic adjustments mediated by redox reactions, probably leading to an ineffective preparatory event that culminates in compensatory liver growth after PH in the rat.

  16. Polyoxometalate active charge-transfer material for mediated redox flow battery

    DOEpatents

    Anderson, Travis Mark; Hudak, Nicholas; Staiger, Chad; Pratt, Harry

    2017-01-17

    Redox flow batteries including a half-cell electrode chamber coupled to a current collecting electrode are disclosed herein. In a general embodiment, a separator is coupled to the half-cell electrode chamber. The half-cell electrode chamber comprises a first redox-active mediator and a second redox-active mediator. The first redox-active mediator and the second redox-active mediator are circulated through the half-cell electrode chamber into an external container. The container includes an active charge-transfer material. The active charge-transfer material has a redox potential between a redox potential of the first redox-active mediator and a redox potential of the second redox-active mediator. The active charge-transfer material is a polyoxometalate or derivative thereof. The redox flow battery may be particularly useful in energy storage solutions for renewable energy sources and for providing sustained power to an electrical grid.

  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. 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.

  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. Engineered Proteins: Redox Properties and Their Applications

    PubMed Central

    Prabhulkar, Shradha; Tian, Hui; Wang, Xiaotang; Zhu, Jun-Jie

    2012-01-01

    Abstract Oxidoreductases and metalloproteins, representing more than one third of all known proteins, serve as significant catalysts for numerous biological processes that involve electron transfers such as photosynthesis, respiration, metabolism, and molecular signaling. The functional properties of the oxidoreductases/metalloproteins are determined by the nature of their redox centers. Protein engineering is a powerful approach that is used to incorporate biological and abiological redox cofactors as well as novel enzymes and redox proteins with predictable structures and desirable functions for important biological and chemical applications. The methods of protein engineering, mainly rational design, directed evolution, protein surface modifications, and domain shuffling, have allowed the creation and study of a number of redox proteins. This review presents a selection of engineered redox proteins achieved through these methods, resulting in a manipulation in redox potentials, an increase in electron-transfer efficiency, and an expansion of native proteins by de novo design. Such engineered/modified redox proteins with desired properties have led to a broad spectrum of practical applications, ranging from biosensors, biofuel cells, to pharmaceuticals and hybrid catalysis. Glucose biosensors are one of the most successful products in enzyme electrochemistry, with reconstituted glucose oxidase achieving effective electrical communication with the sensor electrode; direct electron-transfer-type biofuel cells are developed to avoid thermodynamic loss and mediator leakage; and fusion proteins of P450s and redox partners make the biocatalytic generation of drug metabolites possible. In summary, this review includes the properties and applications of the engineered redox proteins as well as their significance and great potential in the exploration of bioelectrochemical sensing devices. Antioxid. Redox Signal. 17, 1796–1822. PMID:22435347

  1. Relation of electrochemical potentials and iron content to ground-water flow patterns

    USGS Publications Warehouse

    Back, William; Barnes, Ivan

    1965-01-01

    This study was undertaken to develop means of measuring oxidation potentials in aquifer systems and to use the measured values in interpreting the behavior of iron in ground water. Anne Arundel County, Md., was selected as the area of study because of the wide range of concentration of iron-nearly zero to about 35 ppm-in the ground water and the rather complete information on the geology and hydrology. The regional geology consists of coastal plain sediments ranging in age from Early Cretaceous through the Recent. Most of the pH and oxidation-potential measurements were made in nonmarine Cretaceous deposits, only a few in the marine Eocene. Iron-bearing minerals in the area are primarily hematite or limonite and glauconite with a small amount of pyrite. Equipment was developed that permits the measurement of oxidation potentials by use of saturated calomel and platinum electrodes in ground-water samples uncontaminated by oxygen of the atmosphere. Measured Eh values range from about +700 mv to -40 mv. Approximately 2 to 3 hours are required to measure a stable or nearly stable oxidation potential. The mineralogy and organic content of the deposits and the ground-water flow pattern are the primary controls on the oxidation potential and pH of the water. A correlation exists between the oxidation potential and the concentration of iron in ground water; the higher concentrations occur in waters with the lowest values of Eh. The concentration of iron in the water tested shows little correlation with the pH of the water. The highest oxidation potentials were measured in water produced from shallow wells and those wells in recharge areas. The lowest potentials were measured farthest downgradient in water associated with gray and green sediments. The Eh values measured in the field are between values predicted from the solubility of Fe(OH)2(c) and values predicted from the solubility of hematite.

  2. Assessment of rosmarinic acid content in six Lamiaceae species extracts and their antioxidant and antimicrobial potential.

    PubMed

    Benedec, Daniela; Hanganu, Daniela; Oniga, Ilioara; Tiperciuc, Brindusa; Olah, Neli-Kinga; Raita, Oana; Bischin, Cristina; Silaghi-Dumitrescu, Radu; Vlase, Laurian

    2015-11-01

    In the present study, six indigenous species of Lamiaceae family (Origanum vulgare L., Melissa officinalis L., Rosmarinus officinalis L., Ocimum basilicum L., Salvia officinalis L. and Hyssopus officinalis L.), have been analyzed to assess the rosmarinic acid, phenyl propane derivatives and polyphenolic contents and their antioxidant and antimicrobial potential. HPLC-MS method has been used for the analysis ofrosmarinicacid. The phenyl propane derivatives and total phenolic contents were determined using spectrophotometric method. The ethanolic extracts were screened for antioxidant activities by DPPH radical scavenging, HAPX (hemoglobin ascorbate per oxidase activity inhibition), and EPR (electron paramagnetic resonance) methods. The ethanolic extracts revealed the presence of rosmarinic acid in the largest amount in O. vulgare (12.40mg/g) and in the lowest in R. officinalis (1.33 mg/g). O. vulgare extracts exhibited the highest antioxidant capacity, in line with the rosmarinic acid and polyphenolic contents. The antimicrobial testing showed a significant activity against L. monocytogenes, S. aureus and C. albicans for all six extracts.

  3. Assessing redox potential of a native tree from the Brazilian Atlantic Rainforest: a successful evaluation of oxidative stress associated to a new power generation source of an oil refinery.

    PubMed

    Esposito, Marisia Pannia; Pedroso, Andrea Nunes Vaz; Domingos, Marisa

    2016-04-15

    The antioxidant responses in saplings of Tibouchina pulchra (a native tree from the Brazilian Atlantic Rainforest) exposed around an oil refinery in the city of Cubatão (SE Brazil), varied during the exchange of its power generation source, from boilers fueled with oil to a thermoelectric fueled with natural gas. The redox potential changed in response to an interaction of air pollution and meteorological parameters, indicating that the pro-oxidant/antioxidant balance was not reached after the exchange of the power generation system. The gain in environmental quality in the region was not achieved as expected due the technological modernization, at least relative to oxidative stressors. These conclusions were based on results of analyses of enzymatic antioxidants: superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), glutathione reductase (GR); non-enzymatic antioxidants: reduced, oxidized and total ascorbic acid (AsA, DHA, totAA) and glutathione (GSH, GSSG, totG), their redox state (AsA/totAA and GSH/totG) and an indicator of lipid peroxidation (MDA). We also applied exploratory multivariate statistics in order to verify if the temporal sequence of changes in the plant redox capacity coincided with changes in the profile of air pollution, climatic conditions or with their interactions and if the environmental benefits that would supposedly be promoted by the mentioned exchange of power generation system were achieved in the region.

  4. Functional aspects of redox control during neuroinflammation.

    PubMed

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

    2010-07-15

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

  5. Redox Bulk Energy Storage System Study, Volume 1

    NASA Technical Reports Server (NTRS)

    Ciprios, G.; Erskine, W., Jr.; Grimes, P. G.

    1977-01-01

    Opportunities were found for electrochemical energy storage devices in the U.S. electric utility industry. Application requirements for these devices were defined, including techno-economic factors. A new device, the Redox storage battery was analyzed. The Redox battery features a decoupling of energy storage and power conversion functions. General computer methods were developed to simulate Redox system operations. These studies showed that the Redox system is potentially attractive if certain performance goals can be achieved. Pathways for reducing the cost of the Redox system were identified.

  6. Organelle Redox of CF and CFTR-Corrected Airway Epithelia

    PubMed Central

    Schwarzer, Christian; Illek, Beate; Suh, Jung H.; Remington, S. James; Fischer, Horst; Machen, Terry E.

    2014-01-01

    In cystic fibrosis reduced CFTR function may alter redox properties of airway epithelial cells. Redox-sensitive GFP (roGFP1) and imaging microscopy were used to measure redox potentials of cytosol, ER, mitochondria and cell surface of cystic fibrosis nasal epithelial cells and CFTR-corrected cells. We also measured glutathione and cysteine thiol redox states in cell lysates and apical fluids to provide coverage over a range of redox potentials and environments that might be affected by CFTR. As measured with roGFP1, redox potentials at the cell surface (~ -207 ±8 mV) and in the ER (~ -217 ±1 mV) and rates of regulation of the apical fluid and ER lumen following DTT treatment were similar for CF and CFTR-corrected cells. CF and CFTR-corrected cells had similar redox potentials in mitochondria (-344 ±9 mV) and cytosol (-322 ±7 mV). Oxidation of carboxy-dichlorodihydrofluoresceindiacetate and of apical Amplex Red occurred at equal rates in CF and CFTR-corrected cells. Glutathione and cysteine redox couples in cell lysates and apical fluid were equal in CF and CFTR-corrected cells. These quantitative estimates of organelle redox potentials combined with apical and cell measurements using small molecule couples confirmed there were no differences in redox properties of CF and CFTR-corrected cells. PMID:17603939

  7. Strong correlations in actinide redox reactions

    NASA Astrophysics Data System (ADS)

    Horowitz, S. E.; Marston, J. B.

    2011-02-01

    Reduction-oxidation (redox) reactions of the redox couples An(VI)/An(V), An(V)/An(IV), and An(IV)/An(III), where An is an element in the family of early actinides (U, Np, and Pu), as well as Am(VI)/Am(V) and Am(V)/Am(III), are modeled by combining density functional theory with a generalized Anderson impurity model that accounts for the strong correlations between the 5f electrons. Diagonalization of the Anderson impurity model yields improved estimates for the redox potentials and the propensity of the actinide complexes to disproportionate.

  8. Redox Flow Batteries: An Engineering Perspective

    SciTech Connect

    Chalamala, Babu R.; Soundappan, Thiagarajan; Fisher, Graham R.; Anstey, Mitchell A.; Viswanathan, Vilayanur V.; Perry, Mike L.

    2014-10-01

    Redox flow batteries are well suited to provide modular and scalable energy storage systems for a wide range of energy storage applications. In this paper, we review the development of redox flow battery technology including recent advances in new redox active materials and systems. We discuss cost, performance, and reliability metrics that are critical for deployment of large flow battery systems. The technology, while relatively young, has the potential for significant improvement through reduced materials costs, improved energy and power efficiency, and significant reduction in the overall system cost.

  9. Strong correlations in actinide redox reactions.

    PubMed

    Horowitz, S E; Marston, J B

    2011-02-14

    Reduction-oxidation (redox) reactions of the redox couples An(VI)/An(V), An(V)/An(IV), and An(IV)/An(III), where An is an element in the family of early actinides (U, Np, and Pu), as well as Am(VI)/Am(V) and Am(V)/Am(III), are modeled by combining density functional theory with a generalized Anderson impurity model that accounts for the strong correlations between the 5f electrons. Diagonalization of the Anderson impurity model yields improved estimates for the redox potentials and the propensity of the actinide complexes to disproportionate.

  10. Antioxidant potential, cytotoxic activity and total phenolic content of Alpinia pahangensis rhizomes

    PubMed Central

    2013-01-01

    Background Alpinia pahangensis, a wild ginger distributed in the lowlands of Pahang, Malaysia, is used by the locals to treat flatulence. In this study, the antioxidant and cytotoxic activities of the crude aqueous methanol and fractionated extracts of Alpinia pahangensis against five different cancer and one normal cell lines were investigated. The total phenolic content of each extract and its fractions were also quantified. This is the first report on the antioxidant and cytotoxic activities of Alpinia pahangensis extract. Methods In the current study, the crude methanol and fractionated extract of the rhizomes of Alpinia pahangensis were investigated for their antioxidant activity using four different assays namely, the DPPH scavenging activity, superoxide anion scavenging, β-carotene bleaching and reducing power assays whilst their phenolic contents were measured by the Folin-Ciocalteu’s method. In vitro neutral red cytotoxicity assay was employed to evaluate the cytotoxic activity against five different cancer cell lines, colon cancer (HCT 116 and HT-29), cervical cancer (Ca Ski), breast cancer (MCF7) and lung cancer (A549) cell lines, and one normal cell line (MRC-5). The extract that showed high cytotoxic activity was further investigated for its chemical constituents by GC-MS (gas chromatography–mass spectrometry) analysis. Results The ethyl acetate fraction showed the strongest DPPH radical scavenging (0.35 ± 0.094 mg/ml) and SOD activities (51.77 ± 4.9%) whilst the methanol extract showed the highest reducing power and also the strongest antioxidant activity in the β-carotene bleaching assays in comparison to other fractions. The highest phenolic content was found in the ethyl acetate fraction, followed by the crude methanol extract, hexane and water fractions. The results showed a positive correlation between total phenolic content with DPPH radical scavenging capacities and SOD activities. The hexane fraction showed potent cytotoxic

  11. Antioxidant, total phenolic contents and antinociceptive potential of Teucrium stocksianum methanolic extract in different animal models

    PubMed Central

    2014-01-01

    Background Oxidative stress and analgesia are connected with different pathological conditions. The drug candidates from synthetic sources are associated with various side effects; therefore, researchers are giving priority to find novel, effective and safe phytomedicines. Teucrium species possesses antioxidant, analgesic, anti-inflammatory and hepatoprotective activities. The essential oils of Teucrium stocksianum have shown strong antinociceptive potential. Our current study is designed to embark total phenolic content (TPC), antioxidant and antinociceptive potential of the methanolic extract of Teucrium stocksianum (METS). Method Phytochemical composition was determined by using standard methods. Free radical scavenging potential and TPC of METS were assessed by using 2, 2-diphenyl-1-picryl-hydrazyl (DPPH) and Folin-Ciocalteu Reagent (FCR) respectively. Antinociceptive potential was determined by acetic acid induced abdominal writhing, formalin induced paw licking and tail immersion tests. Different test dose 50, 100 and 150 mg/kg body weight of METS were administered intra peritonealy (i.p) to various groups of mice for the evaluation of analgesic potential. Results Phytochemical screening confirmed the presence of flavonoids, tannins, saponins, anthraquinone, steroid, phlobatannin, terpenoid, glycoside and reducing sugars. METS was found safe at a dose of 1000 mg/kg body weight. A concentration dependent free radical scavenging effect was observed with methanolic aerial parts extract of Teucrium stocksianum (MAPETS) and methanolic roots extracts of Teucrium stocksianum (MRETS). MAPETS and MRETS have shown highest antioxidant activity 91.72% and 86.19% respectively at 100 μg/ml. MAPETS was found more rich (115.32 mg of GAE/g of dry material) in TPC as compared to MAPETS (105.41 mg of GAE/g). METS demonstrated a dose dependent antinociceptive potential in different pain models, like in acetic acid, formalin and tail immersion showing 83.103%, 80.872% and 67

  12. Antioxidant potential and total phenolic content of methanolic bark extract of Madhuca indica (koenig) Gmelin

    PubMed Central

    Chaudhary, Anu; Bhandari, Anil; Pandurangan, A.

    2012-01-01

    This study was carried out to investigate the antioxidant and free radical scavenging activity of methanolic extract of Madhuca indica bark in varios systems. DPPH radical, superoxide anion radical, nitric oxide radical, hydroxyl radical, lipid peroxidation, and total phenolic content assays were carried out to evaluate the antioxidant potential of the extract. The percentage inhibition of 40 μg/ml concentration of MMI in DPPH radical scavenging model was found as 74.1%. The scavenging of nitric oxide by the plant extract was concentration dependent and IC50 value of rutin was found to be 161.7 μg/ml. MMI elicited significant and concentration-dependent superoxide radical scavenging effect with MMI as well as standard curcumin, which exhibited IC50 values of 38.1 and 5.84 μg/ml, respectively. MMI demonstrated significant scavenging activity of OH- radical generated from Fe2+-ascorbate-EDTA-H2O2 in a concentration-dependent manner. The extract showed a significant dose-dependent free radical scavenging activity in all the models. The extract showed the presence of high phenolic content corresponding to 98.48 μg equivalent of gallic acid and the antioxidant activity could be attributed to this. PMID:23284220

  13. The ACACA gene is a potential candidate gene for fat content in sheep milk.

    PubMed

    Moioli, B; Scatà, M C; De Matteis, G; Annicchiarico, G; Catillo, G; Napolitano, F

    2013-08-01

    No major gene has yet been reported in sheep that explains the variation of milk fat content. The coding region of the acetyl-CoA carboxylase alpha (ACACA) gene, which plays an important role in de novo fatty acid synthesis, had been investigated, but no non-synonymous mutations have been reported. In this study, the genomic regions encoding the three promoters of the ACACA gene were directly sequenced in 264 sheep of three different breeds, and 10 SNPs were identified. Allele frequencies of most SNPs significantly differed (P = 0.05-0.0001) between breeds. The SNPs that potentially altered either gene regulatory elements or putative binding sites of transcription factors were made evident through in silico analysis. The association analysis with milk traits, performed for one SNP of PIII (GenBank AJ292286, g.1330G>T), showed a significant allelic substitution effect (+0.33%, P < 0.0001 and +0.35%, P < 0.01) in the Altamurana and Gentile breeds respectively. Because this SNP was located in the binding site of the paired box protein transcription factors, which was shown to function as an efficient promoter element, and because PIII transcripts are expressed in the mammary gland, the SNP in PIII of the ACACA gene might affect the variation of fat content in sheep milk.

  14. Anti-Proliferation Potential and Content of Fucoidan Extracted from Sporophyll of New Zealand Undaria pinnatifida.

    PubMed

    Mak, Wilfred; Wang, Sheng Kelvin; Liu, Tingting; Hamid, Nazimah; Li, Yan; Lu, Jun; White, William Lindsey

    2014-01-01

    Undaria pinnatifida is a species of brown seaweed known to contain rich amounts of fucoidan, a sulfated polysaccharide known to possess various biological activities. We isolated crude fucoidan (F0) from the sporophylls of U. pinnatifida grown in the Marlborough Sounds, New Zealand. Sulfate content, uronic acid content, and molecular weight of F0 were 15.02, 1.24, and >150 kDa, respectively. F0 was fractionated to yield three further fractions: F1, F2, and F3. Cytotoxicity of two major fractions was determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The algal fucoidans specifically suppressed the proliferation of three cancer cell lines with less cytotoxicity against the normal cells. Selective cytotoxicity could relate to the distinctive structures of each fucoidan fraction. Results from this study provide evidence that fucoidan, especially from U. pinnatifida grown in New Zealand, possesses great potential to be used as a functional food to reduce cancer risk or supplement cancer treatment.

  15. Enhancing Phenolic Contents and Antioxidant Potentials of Antidesma thwaitesianum by Supercritical Carbon Dioxide Extraction

    PubMed Central

    Poontawee, Warut; Natakankitkul, Surapol; Wongmekiat, Orawan

    2015-01-01

    Supercritical fluid extraction (SFE) has increasingly gained attention as an alternative technique for extraction of natural products without leaving toxic residues in extracts. Antidesma thwaitesianum Muell. Arg. (Phyllanthaceae), or ma mao, has been reported to exhibit antioxidant health benefits due to its phenolic constituents. To determine whether SFE technique could impact on phenolic contents and associated antioxidant potentials, ripe fruits of Antidesma thwaitesianum (Phyllanthaceae) were extracted using supercritical carbon dioxide (SC-CO2) and conventional solvents (ethanol, water). The results showed that the SC-CO2 extract contained significantly higher yield, total phenolic, flavonoid, and proanthocyanidin contents than those obtained from ethanol and water. It also demonstrated the greatest antioxidant activities as assessed by ABTS radical cation decolorization, DPPH radical scavenging, and ferric reducing antioxidant power (FRAP) assays. Further analysis using high-performance liquid chromatography with diode array and mass spectrometry detectors (HPLC-DAD/MSD) revealed the presence of catechin as a major phenolic compound of Antidesma thwaitesianum (Phyllanthaceae), with the maximum amount detected in the SC-CO2 extract. These data indicate that SFE technology improves both quantity and quality of Antidesma thwaitesianum fruit extract. The findings added more reliability of using this technique to produce high added value products from this medicinal plant. PMID:25977832

  16. BOREAS TE-6 Predawn Leaf Water Potentials and Foliage Moisture Contents

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Curd, Shelaine (Editor); Vogel, Jason G.

    2000-01-01

    The BOREAS TE-6 team collected several data sets to examine the influence of vegetation, climate, and their interactions on the major carbon fluxes for boreal forest species. This data set contains summaries of predawn leaf water potentials and foliage moisture contents collected at the TF and CEV sites that had canopy access towers. The data were collected on a nearly weekly basis from early June to late August 1994 by TE-06, members of the BOREAS staff, and employees of Environment Canada. The data are provided in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Activity Archive Center (DAAC).

  17. Measurements of water potential and water content in unsaturated crystalline rock

    NASA Astrophysics Data System (ADS)

    Schneebeli, Martin; Flühler, Hannes; Gimmi, Thomas; Wydler, Hannes; LäSer, Hans-Peter; Baer, Toni

    1995-08-01

    A water desaturation zone develops around a tunnel in water-saturated rock when the evaporative water loss at the rock surface is larger than the water flow from the surrounding saturated region of restricted permeability. We describe the methods with which such water desaturation processes in rock materials can be quantified. The water retention characteristic θ (ψ) of crystalline rock samples was determined with a pressure membrane apparatus. The negative water potential, identical to the capillary pressure, ψ, below the tensiometric range (ψ < -0.1 MPa) can be measured with thermocouple psychrometers (TP), and the volumetric water contents, θ, by means of time domain reflectometry (TDR). These standard methods were adapted for measuring the water status in a macroscopically unfissured granodiorite with a total porosity of approximately 0.01. The measured water retention curve of granodiorite samples from the Grimsel test site (central Switzerland) exhibits a shape which is typical for bimodal pore size distributions. The measured bimodality is probably an artifact of a large surface ratio of solid/voids. The thermocouples were installed without a metallic screen using the cavity drilled into the granodiorite as a measuring chamber. The water potentials observed in a cylindrical granodiorite monolith ranged between -0.1 and -3.0 MPa; those near the wall in a ventilated tunnel between -0.1 and -2.2 MPa. Two types of three-rod TDR probes were used, one as a depth probe inserted into the rock, the other as a surface probe using three copper stripes attached to the surface for detecting water content changes in the rock-to-air boundary. The TDR signal was smoothed with a low-pass filter, and the signal length determined based on the first derivative of the trace. Despite the low porosity of crystalline rock these standard methods are applicable to describe the unsaturated zone in solid rock and may also be used in other consolidated materials such as concrete.

  18. Training Content and Potential Impact on Performance: A Comparison of Young Male and Female Endurance-Trained Runners

    ERIC Educational Resources Information Center

    Garcin, M.; Fleury, A.; Ansart, N.; Mille-Hamard, L.; Billat, V.

    2006-01-01

    The purpose of the present investigation was to compare the content of 8 weeks of training in young endurance-trained male and female runners and study the potential impact of this training content on performance. Fourteen men and 11 women performed two criterion exercises until exhaustion on an outdoor track before and after the 8-week training…

  19. Redox regulation: an introduction.

    PubMed

    Dietz, Karl-Josef; Scheibe, Renate

    2004-01-01

    The redox-state is a critical determinate of cell function, and any major imbalances can cause severe damage or death. The cellular redox status therefore needs to be sensed and modulated before such imbalances occur. Various redox-active components are involved in these processes, including thioredoxins, glutaredoxins and other thiol/disulphide-containing proteins. The cellular reactions for cytoprotection and for signalling are integrated with physiological redox-reactions in photosynthesis, assimilation and respiration. They also determine the developmental fate of the cell and finally decide on proliferation or cell death. An international workshop on redox regulation, organized by the research initiative FOR 387 of the Deutsche Forschungsgemeinschaft, was held in Bielefeld, Germany in 2002. A selection of articles originating from the meeting is printed in this issue of Physiologia Plantarum.

  20. Anti-adenovirus activity, antioxidant potential, and phenolic content of black tea (Camellia sinensis Kuntze) extract.

    PubMed

    Karimi, Ali; Moradi, Mohammad-Taghi; Alidadi, Somayeh; Hashemi, Leila

    2016-12-01

    BackgroundAdenovirus (ADV) causes a number of diseases in human, and to date, no specific antiviral therapy is approved against this virus. Thus, searching for effective anti-ADV agents seems to be an urgent requirement. Many studies have shown that components derived from medicinal plants have antiviral activity. Therefore, the present study was aimed to evaluate in vitro anti-ADV activity and also antioxidant potential and total phenolic compounds of black tea (Camellia sinensis) crude extract. MethodsIn this study, the hydroalchoholic extract of black tea was prepared and its anti-ADV activity was evaluated on HEp2 cell line using MTT [3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide] assay. The 50 % inhibitory concentration (IC50) and 50 % cytotoxicity concentration (CC50) of the extract were determined using regression analysis. Its inhibitory effect on adsorption and/or post-adsorption stages of the virus replication cycle was evaluated. To determine antioxidant activity, total phenol content, and flavonoids content of the extract, the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, Folin-Ciocalteu method, and aluminum chloride colorimetric method were used, respectively. ResultsThe CC50 and the IC50 of the extract were 165.95±12.7 and 6.62±1.4 µg/mL, respectively, with the selectivity index (SI) of 25.06. This extract inhibited ADV replication in post-adsorption stage. The IC50 of DPPH radical was 8±1.41 μg/mL, compared with butylated hydroxytoluene, with IC50 of 25.41±1.89 μg/mL. The total phenol and flavonoid contents of the extract were 341.8±4.41 mg gallic acid equivalent per gram and 21.1±2.11 mg/g, respectively. ConclusionsHaving SI value of 25.06 with inhibitory effect on ADV replication, particularly during the post-adsorption period, black tea extract could be considered as a potential anti-ADV agent. The antiviral activity of this extract could be attributed to its phenolic compounds.

  1. A Low Glutathione Redox State Couples with a Decreased Ascorbate Redox Ratio to Accelerate Flowering in Oncidium Orchid.

    PubMed

    Chin, Dan-Chu; Hsieh, Chia-Chi; Lin, Hsin-Yi; Yeh, Kai-Wun

    2016-02-01

    Glutathione (GSH) plays multiple roles in plants, including stress defense and regulation of growth/development. Previous studies have demonstrated that the ascorbate (AsA) redox state is involved in flowering initiation in Oncidium orchid. In this study, we discovered that a significantly decreased GSH content and GSH redox ratio are correlated with a decline in the AsA redox state during flowering initiation and high ambient temperature-induced flowering. At the same time, the expression level and enzymatic activity of GSH redox-regulated genes, glutathione reductase (GR1), and the GSH biosynthesis genes γ-glutamylcysteine synthetase (GSH1) and glutathione synthase (GSH2), are down-regulated. Elevating dehydroascorbate (DHA) content in Oncidium by artificial addition of DHA resulted in a decreased AsA and GSH redox ratio, and enhanced dehydroascorbate reductase (DHAR) activity. This demonstrated that the lower GSH redox state could be influenced by the lower AsA redox ratio. Moreover, exogenous application of buthionine sulfoximine (BSO), to inhibit GSH biosynthesis, and glutathione disulfide (GSSG), to decrease the GSH redox ratio, also caused early flowering. However, spraying plants with GSH increased the GSH redox ratio and delayed flowering. Furthermore, transgenic Arabidopsis overexpressing Oncidium GSH1, GSH2 and GR1 displayed a high GSH redox ratio as well as delayed flowering under high ambient temperature treatment, while pad2, cad2 and gr1 mutants exhibited early flowering and a low GSH redox ratio. In conclusion, our results provide evidence that the decreased GSH redox state is linked to the decline in the AsA redox ratio and mediated by down-regulated expression of GSH metabolism-related genes to affect flowering time in Oncidium orchid.

  2. Toward high-content screening of mitochondrial morphology and membrane potential in living cells.

    PubMed

    Iannetti, Eligio F; Willems, Peter H G M; Pellegrini, Mina; Beyrath, Julien; Smeitink, Jan A M; Blanchet, Lionel; Koopman, Werner J H

    2015-06-01

    Mitochondria are double membrane organelles involved in various key cellular processes. Governed by dedicated protein machinery, mitochondria move and continuously fuse and divide. These "mitochondrial dynamics" are bi-directionally linked to mitochondrial and cell functional state in space and time. Due to the action of the electron transport chain (ETC), the mitochondrial inner membrane displays a inside-negative membrane potential (Δψ). The latter is considered a functional readout of mitochondrial "health" and required to sustain normal mitochondrial ATP production and mitochondrial fusion. During the last decade, live-cell microscopy strategies were developed for simultaneous quantification of Δψ and mitochondrial morphology. This revealed that ETC dysfunction, changes in Δψ and aberrations in mitochondrial structure often occur in parallel, suggesting they are linked potential targets for therapeutic intervention. Here we discuss how combining high-content and high-throughput strategies can be used for analysis of genetic and/or drug-induced effects at the level of individual organelles, cells and cell populations. This article is part of a Directed Issue entitled: Energy Metabolism Disorders and Therapies.

  3. Cephalosporin-induced alteration in hepatic glutathione redox state. A potential mechanism for inhibition of hepatic reduction of vitamin K1,2,3-epoxide in the rat.

    PubMed Central

    Mitchell, M C; Mallat, A; Lipsky, J J

    1990-01-01

    Hypoprothrombinemia is a serious adverse effect of antimicrobial therapy that occurs after administration of some second- and third-generation cephalosporins which contain the methyltetrazole-thiol (MTT) group. Previous studies have shown that in vitro MTT directly inhibits microsomal gamma-carboxylation of a synthetic pentapeptide. Since MTT is a thiocarbamide, a type of compound that can increase oxidation of glutathione, the present studies were carried out to determine whether alterations in hepatic glutathione redox state might interfere with vitamin K metabolism. Dose-related increases in biliary efflux and hepatic concentration of oxidized glutathione (GSSG) occurred after intravenous administration of MTT or MTT-containing antibiotics to rats. This finding suggested that these compounds could alter the hepatic glutathione redox state in vivo. Microsomal reduction of vitamin K epoxide occurred in the presence of 100 microM dithiothreitol (DTT), but was inhibited by preincubation with GSSG at concentrations as low as 10 microM. At higher concentrations of DTT (1.0 mM) inhibition by GSSG persisted, but higher concentrations were required, suggesting that the thiol/disulfide ratio, rather than the absolute concentration of GSSG was important. By contrast, GSSG did not effect microsomal gamma-carboxylation of a pentapeptide, using either vitamin K1 or its hydroquinone as a cofactor. These findings suggest a novel mechanism for the hypoprothrombinemia occurring after administration of MTT-containing antibiotics. PMID:1978724

  4. The Danish National Patient Registry: a review of content, data quality, and research potential

    PubMed Central

    Schmidt, Morten; Schmidt, Sigrun Alba Johannesdottir; Sandegaard, Jakob Lynge; Ehrenstein, Vera; Pedersen, Lars; Sørensen, Henrik Toft

    2015-01-01

    Background The Danish National Patient Registry (DNPR) is one of the world’s oldest nationwide hospital registries and is used extensively for research. Many studies have validated algorithms for identifying health events in the DNPR, but the reports are fragmented and no overview exists. Objectives To review the content, data quality, and research potential of the DNPR. Methods We examined the setting, history, aims, content, and classification systems of the DNPR. We searched PubMed and the Danish Medical Journal to create a bibliography of validation studies. We included also studies that were referenced in retrieved papers or known to us beforehand. Methodological considerations related to DNPR data were reviewed. Results During 1977–2012, the DNPR registered 8,085,603 persons, accounting for 7,268,857 inpatient, 5,953,405 outpatient, and 5,097,300 emergency department contacts. The DNPR provides nationwide longitudinal registration of detailed administrative and clinical data. It has recorded information on all patients discharged from Danish nonpsychiatric hospitals since 1977 and on psychiatric inpatients and emergency department and outpatient specialty clinic contacts since 1995. For each patient contact, one primary and optional secondary diagnoses are recorded according to the International Classification of Diseases. The DNPR provides a data source to identify diseases, examinations, certain in-hospital medical treatments, and surgical procedures. Long-term temporal trends in hospitalization and treatment rates can be studied. The positive predictive values of diseases and treatments vary widely (<15%–100%). The DNPR data are linkable at the patient level with data from other Danish administrative registries, clinical registries, randomized controlled trials, population surveys, and epidemiologic field studies – enabling researchers to reconstruct individual life and health trajectories for an entire population. Conclusion The DNPR is a valuable

  5. 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

  6. Development of pyridine-containing macrocyclic copper(II) complexes: potential role in the redox modulation of oxaliplatin toxicity in human breast cells.

    PubMed

    Fernandes, Ana S; Costa, Judite; Gaspar, Jorge; Rueff, José; Cabral, M Fátima; Cipriano, Madalena; Castro, Matilde; Oliveira, Nuno G

    2012-09-01

    The unique redox and catalytic chemistry of Cu has justified the development of novel Cu complexes for different therapeutic uses including cancer therapy. In this work, four pyridine-containing aza-macrocyclic copper(II) complexes were prepared (CuL1-CuL4) varying in ring size and/or substituents and their superoxide scavenging activity evaluated. CuL3, the most active superoxide scavenger, was further studied as a modulator of the cytotoxicity of oxaliplatin in epithelial breast MCF10A cells and in MCF7 breast cancer cells. Our results show that CuL3 enhances the therapeutic window of oxaliplatin, by both protecting non-tumour cells and increasing its cytotoxic effect in breast carcinoma cells. CuL3 is thus a promising complex to be further studied and to be used as a lead compound for the optimization of novel chemotherapy sensitizers.

  7. In-depth process understanding of RECOMBIVAX HB® maturation and potential epitope improvements with redox treatment: multifaceted biochemical and immunochemical characterization.

    PubMed

    Zhao, Qinjian; Towne, Victoria; Brown, Martha; Wang, Yang; Abraham, Dicky; Oswald, C Brent; Gimenez, Juan A; Washabaugh, Michael W; Kennedy, Ronald; Sitrin, Robert D

    2011-10-19

    Recombinant Hepatitis B surface antigen virus-like particles (VLPs) produced in yeast undergo spontaneous maturation during the vaccine production process, and the biophysical characteristics of the particles with respect to maturation were described in Zhao et al. (2006) [13]. Here we report additional biochemical and immunochemical characterization by various techniques, including the use of a panel of monoclonal antibodies (mAbs) that differ in their selectivity and conformation-sensitivity, for probing surface epitope structures. Crosslinking via interchain disulfide formation and binding of conformational specific antibodies in the mature particles were shown to be progressively enhanced. We show that redox-mediated VLP maturation is superior to heat-induced maturation in terms of generating VLPs which exhibit more complete crosslinking (>95%) and 2- to 3-fold higher antigenicity as defined by conformational antibodies. Therefore, the resulting VLPs from redox treatment resemble more closely their plasma-derived counterparts. The value of using multiple mAbs for probing surface epitopes was clearly demonstrated as different mAbs showed different degrees of sensitivity to the structural changes during HBsAg VLP maturation. The rapid, label-free technology of surface plasmon resonance performed at a single antigen concentration was shown to correlate well with a sandwich ELISA using parallel line analysis, currently implemented for product release and stability testing of RECOMBIVAX HB(®). Surface plasmon resonance offers both convenience and flexibility; multiple mAbs can be tested one at a time in the same set of experiments, providing a means to assess changes to individual epitopes. Taken together, these quantitative analytical tools enable more rapid, in-depth, and comprehensive process monitoring, process optimization, and assessment of product consistency and stability.

  8. Disturbance of brain energy and redox homeostasis provoked by sulfite and thiosulfate: potential pathomechanisms involved in the neuropathology of sulfite oxidase deficiency.

    PubMed

    Grings, Mateus; Moura, Alana Pimentel; Parmeggiani, Belisa; Marcowich, Gustavo Flora; Amaral, Alexandre Umpierrez; de Souza Wyse, Angela Terezinha; Wajner, Moacir; Leipnitz, Guilhian

    2013-12-01

    Sulfite oxidase (SO) deficiency is biochemically characterized by tissue accumulation and high urinary excretion of sulfite, thiosulfate and S-sulfocysteine. Affected patients present severe neurological symptoms and cortical atrophy, whose pathophysiology is still poorly established. Therefore, in the present work we investigated the in vitro effects of sulfite and thiosulfate on important parameters of energy metabolism in the brain of young rats. We verified that sulfite moderately inhibited the activity of complex IV, whereas thiosulfate did not alter any of the activities of the respiratory chain complexes. It was also found that sulfite and thiosulfate markedly reduced the activity of total creatine kinase (CK) and its mitochondrial and cytosolic isoforms, suggesting that these metabolites impair brain cellular energy buffering and transfer. In contrast, the activity of synaptic Na(+),K(+)-ATPase was not altered by sulfite or thiosulfate. We also observed that the inhibitory effect of sulfite and thiosulfate on CK activity was prevented by melatonin, reduced glutathione and the combination of both antioxidants, as well as by the nitric oxide synthase N(ω)-nitro-l-arginine methyl ester, indicating the involvement of reactive oxygen and nitrogen species in these effects. Sulfite and thiosulfate also increased 2',7'-dichlorofluorescin oxidation and hydrogen peroxide production and decreased the activity of the redox sensor aconitase enzyme, reinforcing a role for oxidative damage in the effects elicited by these metabolites. It may be presumed that the disturbance of cellular energy and redox homeostasis provoked by sulfite and thiosulfate contributes to the neurological symptoms and abnormalities found in patients affected by SO deficiency.

  9. Scientific issues and potential remote-sensing requirements for plant biochemical content

    NASA Technical Reports Server (NTRS)

    Peterson, David L.; Hubbard, G. S.

    1992-01-01

    Application of developments in imaging spectrometry to the study of terrestrial ecosystems, which began in 1983, demonstrate the potential to estimate lignin and nitrogen concentrations of plant canopies by remote-sensing techniques. Estimation of these parameters from the first principles of radiative transfer and the interactions of light with plant materials is not presently possible, principally because of lack of knowledge about internal leaf scattering and specific absorption involving biochemical compounds. From the perspective of remote-sensing instrumentation, sensors are needed to support derivative imaging spectroscopy. Biochemical absorption features tend to occur in functional groupings throughout the 1100- to 2500-nm region. Derivative spectroscopy improves the information associated with the weaker, narrower absorption features of biochemical absorption that are superimposed on the strong absolute variations due to foliar biomass, pigments, and leaf water content of plant canopies. Preliminary sensor specifications call for 8-nm bandwidths at 2-nm centers in four spectral regions (about 400 bands total) and a signal-to-noise performance of at least 1000:1 for 20 percent albedo targets in the 2000-nm region.

  10. Cadmium content of commercial and contaminated rice, Oryza sativa, in Thailand and potential health implications.

    PubMed

    Zwicker, R; Promsawad, A; Zwicker, B M; Laoharojanaphand, S

    2010-03-01

    Thailand is the number one global exporter and among the top five producers of rice in the world. A significant increase in anthropogenic contamination in agricultural soils over the past few decades has lead to concerns with cadmium and its uptake in rice. The cadmium levels in Thai rice from different sources/areas were determined and used to estimate the potential health risks to consumers. The cadmium concentration in the commercial rice samples ranged from below the detection limit to 0.016 mg/kg. The cadmium concentrations in the contaminated rice samples ranged from a low of 0.007 mg/kg to a high of 0.579 mg/kg. Five of the calculated values exceed the proposed PTWI, with one value almost three times higher and two values almost double. The three highly elevated values are certainly a concern from a health standpoint. Ultimately, action is required to address the health implications resulting from the cadmium contamination in agricultural soils used for rice production in a few select areas of Thailand. Overall, this study indicates that the vast majority of rice produced, consumed and exported by Thailand is safe pertaining to cadmium content.

  11. Effects of negative content on the processing of gender information: an event-related potential study.

    PubMed

    Hinojosa, José A; Albert, Jacobo; Fernández-Folgueiras, Uxía; Santaniello, Gerardo; López-Bachiller, Cristina; Sebastián, Manuel; Sánchez-Carmona, Alberto J; Pozo, Miguel A

    2014-12-01

    Previous research on emotion in language has mainly concerned the impact of emotional information on several aspects of lexico-semantic analyses of single words. However, affective influences on morphosyntactic processing are less understood. In the present study, we focused on the impact of negative valence in the processing of gender agreement relations. Event-related potentials (ERPs) were recorded while participants read three-word phrases and performed a syntactic judgment task. Negative and neutral adjectives could agree or disagree in gender with the preceding noun. At an electrophysiological level, the amplitude of a left anterior negativity (LAN) to gender agreement mismatches decreased in negative words, relative to neutral words. The behavioral data suggested that LAN amplitudes might be indexing the processing costs associated with the detection of gender agreement errors, since the detection of gender mismatches resulted in faster and more accurate responses than did the detection of correct gender agreement relations. According to this view, it seems that negative content facilitated the processes implicated in the early detection of gender agreement mismatches. However, gender agreement violations in negative words triggered processes involved in the reanalysis and repair of the syntactic structure, as reflected in larger P600 amplitudes to incorrect than to correct phrases, irrespective of their emotional valence.

  12. Physicochemical and redox characteristics of particulate matter (PM) emitted from gasoline and diesel passenger cars

    NASA Astrophysics Data System (ADS)

    Geller, Michael D.; Ntziachristos, Leonidas; Mamakos, Athanasios; Samaras, Zissis; Schmitz, Debra A.; Froines, John R.; Sioutas, Constantinos

    Particulate matter (PM) originating from mobile sources has been linked to a myriad of adverse health outcomes, ranging from cancer to cardiopulmonary disease, and an array of environmental problems, including global warming and acid rain. Till date, however, it is not clear which physical characteristics or chemical constituents of PM are significant contributors to the magnitude of the health risk. This study sought to determine the relationship between physical and chemical characteristics of PM while quantitatively measuring samples for redox activity of diesel and gasoline particulate emissions from passenger vehicles typically in use in Europe. The main objective was to relate PM chemistry to the redox activity in relation to vehicle type and driving cycle. Our results showed a high degree of correlation between several PM species, including elemental and organic carbon, low molecular weight polycyclic aromatic hydrocarbons, and trace metals such as lithium, beryllium, nickel and zinc, and the redox activity of PM, as measured by a quantitative chemical assay, the dithiothreitol (DTT) assay. The reduction in PM mass or number emission factors resulting from the various engine configurations, fuel types and/or after-treatment technologies, however, was non-linearly related to the decrease in overall PM redox activity. While the PM mass emission rate from the diesel particle filter (DPF)-equipped vehicle was on average approximately 25 times lower than that of the conventional diesel, the redox potential was only eight times lower, which makes the per mass PM redox potential of the DPF vehicle about three times higher. Thus, a strategy aimed at protecting public health and welfare by reducing total vehicle mass and number emissions may not fully achieve the desired goal of preventing the health consequences of PM exposure. Further, study of the chemical composition and interactions between various chemical species may yield greater insights into the toxicity of

  13. Effects of vine water status on dimethyl sulfur potential, ammonium, and amino acid contents in Grenache Noir grapes (Vitis vinifera).

    PubMed

    De Royer Dupré, N; Schneider, R; Payan, J C; Salançon, E; Razungles, A

    2014-04-02

    We studied the effect of vine water status on the dimethyl sulfur potential (DMSP), ammonium, and amino acid contents of the berry during the maturation of Grenache Noir grapes. Water deficit increased the accumulation of amino acids in berries and favored yeast assimilable amino nitrogen. Similarly, ammonium content was higher in berries from vines subjected to moderate water deficit. DMSP content followed the same trend as yeast assimilable amino acid content, with higher concentrations observed in the berries of vines subjected to water deficit. The high DMSP and yeast assimilable nitrogen contents of musts from vines subjected to water deficit resulted in a better preservation of DMSP during winemaking. The wines produced from these musts had a higher DMSP level and would therefore probably have a higher aroma shelf life, because the DMSP determines the rate of release of dimethyl sulfur during wine storage, and this compound enhances fruity notes.

  14. Alternative functions of the brain transsulfuration pathway represent an underappreciated aspect of brain redox biochemistry with significant potential for therapeutic engagement.

    PubMed

    Hensley, Kenneth; Denton, Travis T

    2015-01-01

    Scientific appreciation for the subtlety of brain sulfur chemistry has lagged, despite understanding that the brain must maintain high glutathione (GSH) to protect against oxidative stress in tissue that has both a high rate of oxidative respiration and a high content of oxidation-prone polyunsaturated fatty acids. In fact, the brain was long thought to lack a complete transsulfuration pathway (TSP) for cysteine synthesis. It is now clear that not only does the brain possess a functional TSP, but brain TSP enzymes catalyze a rich array of alternative reactions that generate novel species including the gasotransmitter hydrogen sulfide (H2S) and the atypical amino acid lanthionine (Lan). Moreover, TSP intermediates can be converted to unusual cyclic ketimines via transamination. Cell-penetrating derivatives of one such compound, lanthionine ketimine (LK), have potent antioxidant, neuroprotective, neurotrophic, and antineuroinflammatory actions and mitigate diverse neurodegenerative conditions in preclinical rodent models. This review will explore the source and function of alternative TSP products, and lanthionine-derived metabolites in particular. The known biological origins of lanthionine and its ketimine metabolite will be described in detail and placed in context with recent discoveries of a GSH- and LK-binding brain protein called LanCL1 that is proving essential for neuronal antioxidant defense; and a related LanCL2 homolog now implicated in immune sensing and cell fate determinations. The review will explore possible endogenous functions of lanthionine metabolites and will discuss the therapeutic potential of lanthionine ketimine derivatives for mitigating diverse neurological conditions including Alzheimer׳s disease, stroke, motor neuron disease, and glioma.

  15. Radioactivity contents in dicalcium phosphate and the potential radiological risk to human populations.

    PubMed

    Casacuberta, N; Masqué, P; Garcia-Orellana, J; Bruach, J M; Anguita, M; Gasa, J; Villa, M; Hurtado, S; Garcia-Tenorio, R

    2009-10-30

    Potentially harmful phosphate-based products derived from the wet acid digestion of phosphate rock represent one of the most serious problems facing the phosphate industry. This is particularly true for dicalcium phosphate (DCP), a food additive produced from either sulphuric acid or hydrochloric acid digestion of raw rock material. This study determined the natural occurring radionuclide concentrations of 12 DCP samples and 4 tricalcium phosphate (TCP) samples used for animal and human consumption, respectively. Metal concentrations (Al, Fe, Zn, Cd, Cr, As, Hg, Pb and Mg) were also determined. Samples were grouped into three different clusters (A, B, C) based on their radionuclide content. Whereas group A is characterized by high activities of 238U, 234U (approximately 10(3) Bq kg(-1)), 210Pb (2 x 10(3) Bq kg(-1)) and (210)Po ( approximately 800 Bq kg(-1)); group B presents high activities of (238)U, (234)U and (230)Th (approximately 10(3) Bq kg(-1)). Group C was characterized by very low activities of all radionuclides (< 50 Bq kg(-1)). Differences between the two groups of DCP samples for animal consumption (groups A and B) were related to the wet acid digestion method used, with group A samples produced from hydrochloric acid digestion, and group B samples produced using sulphuric acid. Group C includes more purified samples required for human consumption. High radionuclide concentrations in some DCP samples (reaching 2 x 10(3) and 10(3) Bq kg(-1) of 210Pb and 210Po, respectively) may be of concern due to direct or indirect radiological exposure via ingestion. Our experimental results based on 210Pb and 210Po within poultry consumed by humans, suggest that the maximum radiological doses are 11 +/- 2 microSv y(-1). While these results suggest that human health risks are small, additional testing should be conducted.

  16. Conformational changes in redox pairs of protein structures

    PubMed Central

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

    2009-01-01

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

  17. Influences of filler content and size on the color adjustment potential of nonlayered resin composites.

    PubMed

    Suh, Yong-Rok; Ahn, Jin-Soo; Ju, Sung-Won; Kim, Kwang-Mahn

    2017-01-31

    The blending effect (BE) plays an important role in esthetics of the composite resin. The objective of this study was to determine the extents to which filler size and content affect the BE. Three types of fillers (0.7, 1.0, and 1.5 µm) were mixed at weight contents of 60, 70, 75, and 80%. This study simulated clinical class 3 or 4 cavities and quantitatively measured the color diffusion of the objects next to the cavities based on the CIELab color space. For each filler size, there was a trend of increasing BE as the filler content was increased. The translucency parameter (TP) exhibited the opposite trend of decreasing (p<0.05) with increases in filler content. The filler size did not affect the BE, and the different filler sizes produced statistically non-significant results in this study. Increases in filler content elevated the opacity of the composite resin and significantly influenced the BE.

  18. Imposed glutathione-mediated redox switch modulates the tobacco wound-induced protein kinase and salicylic acid-induced protein kinase activation state and impacts on defence against Pseudomonas syringae.

    PubMed

    Matern, Sanja; Peskan-Berghoefer, Tatjana; Gromes, Roland; Kiesel, Rebecca Vazquez; Rausch, Thomas

    2015-04-01

    The role of the redox-active tripeptide glutathione in plant defence against pathogens has been studied extensively; however, the impact of changes in cellular glutathione redox potential on signalling processes during defence reactions has remained elusive. This study explored the impact of elevated glutathione content on the cytosolic redox potential and on early defence signalling at the level of mitogen-activated protein kinases (MAPKs), as well as on subsequent defence reactions, including changes in salicylic acid (SA) content, pathogenesis-related gene expression, callose depositions, and the hypersensitive response. Wild-type (WT) Nicotiana tabacum L. and transgenic high-glutathione lines (HGL) were transformed with the cytosol-targeted sensor GRX1-roGFP2 to monitor the cytosolic redox state. Surprisingly, HGLs displayed an oxidative shift in their cytosolic redox potential and an activation of the tobacco MAPKs wound-induced protein kinase (WIPK) and SA-induced protein kinase (SIPK). This activation occurred in the absence of any change in free SA content, but was accompanied by constitutively increased expression of several defence genes. Similarly, rapid activation of MAPKs could be induced in WT tobacco by exposure to either reduced or oxidized glutathione. When HGL plants were challenged with adapted or non-adapted Pseudomonas syringae pathovars, the cytosolic redox shift was further amplified and the defence response was markedly increased, showing a priming effect for SA and callose; however, the initial and transient hyperactivation of MAPK signalling was attenuated in HGLs. The results suggest that, in tobacco, MAPK and SA signalling may operate independently, both possibly being modulated by the glutathione redox potential. Possible mechanisms for redox-mediated MAPK activation are discussed.

  19. The Chemistry of Redox-Flow Batteries.

    PubMed

    Noack, Jens; Roznyatovskaya, Nataliya; Herr, Tatjana; Fischer, Peter

    2015-08-17

    The development of various redox-flow batteries for the storage of fluctuating renewable energy has intensified in recent years because of their peculiar ability to be scaled separately in terms of energy and power, and therefore potentially to reduce the costs of energy storage. This has resulted in a considerable increase in the number of publications on redox-flow batteries. This was a motivation to present a comprehensive and critical overview of the features of this type of batteries, focusing mainly on the chemistry of electrolytes and introducing a thorough systematic classification to reveal their potential for future development.

  20. Organic non-aqueous cation-based redox flow batteries

    SciTech Connect

    Jansen, Andrew N.; Vaughey, John T.; Chen, Zonghai; Zhang, Lu; Brushett, Fikile R.

    2016-03-29

    The present invention provides a non-aqueous redox flow battery comprising a negative electrode immersed in a non-aqueous liquid negative electrolyte, a positive electrode immersed in a non-aqueous liquid positive electrolyte, and a cation-permeable separator (e.g., a porous membrane, film, sheet, or panel) between the negative electrolyte from the positive electrolyte. During charging and discharging, the electrolytes are circulated over their respective electrodes. The electrolytes each comprise an electrolyte salt (e.g., a lithium or sodium salt), a transition-metal free redox reactant, and optionally an electrochemically stable organic solvent. Each redox reactant is selected from an organic compound comprising a conjugated unsaturated moiety, a boron cluster compound, and a combination thereof. The organic redox reactant of the positive electrolyte is selected to have a higher redox potential than the redox reactant of the negative electrolyte.

  1. Redox Heterogenity in MORB

    NASA Astrophysics Data System (ADS)

    Cottrell, E.; Kelley, K. A.

    2012-12-01

    Mantle oxygen fugacity (fO2) has a first-order effect on the petrogenesis of mantle-derived melts and the speciation of mantle fluids. Current debate centers on the spatial uniformity of upper mantle fO2 and its constancy through geologic time. We use iron K-edge X-ray absorption near-edge structure (μXANES) spectroscopy to provide Fe3+ /ΣFe ratios of submarine mantle-derived basalts from mid-ocean ridges (MORB) as a proxy for fO2. A global survey of primitive (>8.75 wt% MgO) MORB glasses at spreading centers, unaffected by plumes, reveals a decrease in Fe3+ /ΣFe ratio of 12% relative with indices of mantle enrichment such as 87/86Sr, 208/204Pb, Ba/La, and Rb/Sr ratios. The strong negative correlation between upper mantle fO2 and enrichment recorded by MORB glasses contrasts with the positive relationship hinted at by abyssal peridotite oxybarometry (e.g. Ballhaus, CMP, 1993) and the general prediction of a positive correlation born of the expectation that Fe3+ can be treated as more incompatible than Fe2+ during mantle melting. These data unequivocally link upper mantle oxidation state to mantle source enrichment. EMORB generation is commonly attributed to subduction-related processes. That EMORB is more reduced than NMORB implies that deeply subducted and recycled lithologies, such as anoxic sediment, may be more reduced than ambient mantle. Negative correlations between traditional tracers of recycled sediment (e.g. +Nb anomaly, high 87/86Sr, high LILE/LREE) and redox support this hypothesis. Preservation of redox signatures on plate-recycling timescales of hundreds of millions to billions of years would require the mantle to be very poorly buffered. Alternatively, MORB Fe3+ /ΣFe ratios may be generated in situ beneath ridges as a function of variable carbon content. The shallow MORB source is too oxidized to stabilize graphite (Cottrell and Kelley, EPSL, 2011) and carbon exists as oxides. Decreasing fO2 with increasing depth eventually stabilizes reduced

  2. Effect of Clay Content and Soil-water Potential On Mobilization and Leaching of Colloids In Unsaturated Macroporous Soil

    NASA Astrophysics Data System (ADS)

    Kjaergaard, C.; de Jonge, L. W.; Moldrup, P.

    The transport of strongly sorbed environmental contaminants may be enhanced due to sorption to mobile soil colloids. The most common source of mobile colloids in soil is the in-situ release of water-dispersible colloids (WDC), however experimental investigations of colloid mobilization in unsaturated macroporous soil are scarce. An understanding of the arrangement of colloids in aggregates, and the influence of clay on the development of the soil fabric and pore-size distributions is essential for the in- terpretation of colloid mobilization in soils. This emphasizes the important role of clay content, when evaluating the susceptibility of soils to release colloids and associated contaminants. This study was conducted to determine the effect of clay content and initial soil- water potential on colloid mobilization and leaching. Intact soil cores were sampled from an arable field at six locations along a naturally occurring texture gradient. Soil dispersibility was investigated using capillary saturation and drainage of field-moist packed aggregates. The amount of WDC in the soil was measured for each com- bination of clay content and initial soil-water potential (-2.5, -98 and -15530 hPa). Mobilization and leaching of colloids was investigated from unsaturated intact soil cores. The soils were irrigated at low intensity (1 mm/h), and effluent sampling was conducted at 5 cm tension. The results showed that colloid dispersion was significantly affected by both clay con- tent and initial soil-water potential. With a soil-water potential of -15530 hPa the col- loid release was generally low and no variation occurred between the soils. With in- creasing soil-water potential there was an increase in the amount of WDC for all soils. The increase in WDC was negatively correlated with clay content. The leaching of colloids from intact soil cores also decreased with increasing clay content at an ini- tial soil-water potential of -98 and -2.5 hPa, and no difference between

  3. Involvement of oxidative stress response genes in redox homeostasis, the level of reactive oxygen species, and ageing in Saccharomyces cerevisiae.

    PubMed

    Drakulic, Tamara; Temple, Mark D; Guido, Ron; Jarolim, Stefanie; Breitenbach, Michael; Attfield, Paul V; Dawes, Ian W

    2005-12-01

    Saccharomyces cerevisiae mutants lacking oxidative stress response genes were used to investigate which genes are required under normal aerobic conditions to maintain cellular redox homeostasis, using intracellular glutathione redox potential (glutathione E(h)) to indicate the redox environment of the cells. Levels of reactive oxygen species (ROS) and mitochondrial membrane potentials (MMP) were also assessed by FACS using dihydroethidium and rhodamine 123 as fluorescent probes. Cells became more oxidised as strains shifted from exponential growth to stationary phase. During both phases the presence of reduced thioredoxin and the activity of glutathione reductase were important for redox homeostasis. Thioredoxin reductase contributed less during exponential phase when there was a strong requirement for active Yap1p transcription factor, but was critical during stationary phase. The absence of ROS detoxification systems, such as catalases or superoxide dismutases, had a lesser effect on glutathione E(h), but a more pronounced effect on ROS levels and MMP. These results reflect the major shift in ROS generation as cells switch from fermentative to respiratory metabolism and also showed that there was not a strong correlation between ROS production, MMP and cellular redox environment. Heterogeneity was detected in populations of strains with compromised anti-oxidant defences, and as cells aged they shifted from one cell type with low ROS content to another with much higher intracellular ROS.

  4. Virtual water content of temperate cereals and maize: Present and potential future patterns

    NASA Astrophysics Data System (ADS)

    Fader, Marianela; Rost, Stefanie; Müller, Christoph; Bondeau, Alberte; Gerten, Dieter

    2010-04-01

    SummaryKnowledge of the virtual water content (VWC) of crops and especially its possible future developments is helpful for improvements in water productivity and water management, which are necessary at global scale due to rising demand for food, the necessity to ease present and future water scarcity, and the reduction of poverty. Using a dynamic global vegetation and water balance model (LPJmL), this study quantifies the VWC of two of the most important crop types worldwide, temperate cereals and maize, at high spatial resolution (0.5°). We analyzed present conditions (1999-2003) and also for the first time also for scenarios of future climate and increasing atmospheric CO 2 concentrations (2041-2070; HadCM3, ECHAM5 and CCSM3 climate models, A2 emissions scenario). VWC presently differs significantly among regions: highest values are common in large parts of Africa (>2 m 3 kg -1), and lowest values were found e.g. for Central Europe (<0.5 m 3 kg -1), indicating that water-use efficiency of crops is much higher in the latter region. The regional patterns of VWC result from complex and interactive processes; the dominant factor is the crop yield level (high VWC values occur most frequently in regions with low yields). Climate change and rising atmospheric CO 2 concentration will have non-uniform effects on crop yields and evapotranspiration. Worldwide VWC patterns will change significantly, with a pronounced regional pattern that reflects primarily the changes in yields as driven mainly by regionally decreasing precipitation, increasing temperature and increasing atmospheric CO 2 concentration. Although globally the water-use efficiency is projected to increase, many regions—including parts of the US, East and Mediterranean Europe, South Africa, Argentina, Australia and South East Asia—are projected to become less water efficient (higher VWC) for at least one of the crop types. CO 2 fertilisation was simulated to generally reduce VWC, though realisation of

  5. Pyrolysis of waste materials: Characterization and prediction of sorption potential across a wide range of mineral contents and pyrolysis temperatures.

    PubMed

    Kah, Melanie; Sun, Huichao; Sigmund, Gabriel; Hüffer, Thorsten; Hofmann, Thilo

    2016-08-01

    Sewage sludge (50% mineral), manure (29%) and wood (<1%) were pyrolyzed at 200, 350 and 500°C with the aim to study the characteristics and sorption potential of materials undergoing pyrolysis across a wide range of mineral contents. A commercial plant-derived biochar (41% mineral) was also considered. The materials were extensively characterized and tested for their sorption towards the model sorbates benzene, naphthalene and pyrene. Plant-derived materials, regardless of their mineral content, developed micropores causing size exclusion of pyrene. Changes in properties and sorption behavior upon pyrolysis were generally consistent for the manure and wood series. A single regression equation developed on our data (including the sorbate hydrophobicity and sorbent polarity) provided excellent prediction of previously reported changes in sorption upon pyrolysis across a wide range of mineral content (up to 500°C). The sewage sludge series, however, followed a particular behavior, possibly due to very high mineral content (up to 67%).

  6. Microbial activity in argillite waste storage cells for the deep geological disposal of French bituminous medium activity long lived nuclear waste: Impact on redox reaction kinetics and potential

    NASA Astrophysics Data System (ADS)

    Albrecht, A.; Leone, L.; Charlet, L.

    2009-04-01

    Micro-organisms are ubiquitous and display remarkable capabilities to adapt and survive in the most extreme environmental conditions. It has been recognized that microorganisms can survive in nuclear waste disposal facilities if the required major (P, N, K) and trace elements, a carbon and energy source as well as water are present. The space constraint is of particular interest as it has been shown that bacteria do not prosper in compacted clay. An evaluation of the different types of French medium and high level waste, in a clay-rich host rock storage environment at a depth between 500 and 600 m, has shown that the bituminous waste is the most likely candidate to accommodate significant microbial activity. The waste consists of a mixture of bitumen (source of bio-available organic matter and H2 as a consequence of its degradation and radiolysis) and nitrates and sulphates kept in a stainless steel container. The assumption, that microbes only have an impact on reaction kinetics needs to be reassessed in the case where nitrates and sulphates are present since both are known not to react at low temperatures without bacterial catalysis. The additional impact of both oxy-anions and their reduced species on redox conditions, radionuclide speciation and mobility gives this evaluation their particular relevance. Storage architecture proposes four primary waste containers positioned into armoured cement over packs and placed with others into the waste storage cell itself composed of a cement mantle enforcing the argillite host rock, the latter being characterized by an excavation damaged zone constricted both in space and in time and a pristine part of 60 m thickness. Bacterial activity within the waste and within the pristine argillite is disregarded because of the low water activity (< 0.7) and the lack of space, respectively. The most probable zones of microbial activity, those likely to develop sustainable biofilms are within the interface zones. A major restriction

  7. Exploring the effect of the Ln(III)/Ln(II) redox potential on C-F activation and on oxidation of some lanthanoid organoamides.

    PubMed

    Deacon, Glen B; Junk, Peter C; Kelly, Rory P; Wang, Jun

    2016-01-28

    The divalent europium complexes, and (L(Me/Et) = p-HC6F4N(CH2)2NMe2/Et2), have been prepared from redox-transmetallation/protolysis (RTP) reactions between Eu metal, Hg(C6F5)2 and L(Me/Et)H in thf. The complexes exhibit close (C)F-Ln interactions and the amide ligands feature tridentate N,N',F chelation. The complexes are thermally robust but on exposure to light they undergo C-F activation. From exposure of to light, the Eu(III) mixed fluoride/oxide cluster, was isolated, but other well-defined C-F activation products have proven elusive due to the stability of Eu(II). Oxidation of [Ln(L(R))2(thf)2] (Ln = Eu, R = Me; Ln = Yb, R = Et) with I2 afforded the heteroleptic iodo complexes, [Ln(L(R))2I(thf)n] (Ln = Eu, n = 1; Ln = Yb, n = 0), and the homoleptic complexes, [Ln(L(R))3]. The formation of the iodo complexes and the heteroleptic complexes appear to occur by different routes. shows interesting structural differences from reported [Ln(L(Et))3] (Ln = La, Ce, Nd) complexes, and highlights an incomplete shift towards N,N' chelation to the much smaller Yb ion. was prepared from a protolysis reaction between [Sm(CH2C6H4-NMe2-o)3] and L(Me)H. Heating a solution of in toluene at 110 °C for three days did not afford any samarium fluoride complex. An RTP reaction with Sm afforded the heteroleptic samarium complex, , in very low yield. From an attempted protolysis reaction between [Sm(DippForm)2(thf)2] and L(Me)H, the mixed ligand samarium fluoride complex, , was isolated. Overall, the instability of Sm(II) precludes control over the C-F activation reactions.

  8. Inhibition of microsomal cortisol production by (-)-epigallocatechin-3-gallate through a redox shift in the endoplasmic reticulum--a potential new target for treating obesity-related diseases.

    PubMed

    Szelényi, Péter; Révész, Katalin; Konta, Laura; Tüttõ, Anna; Mandl, József; Kereszturi, Éva; Csala, Miklós

    2013-01-01

    Conversion of cortisone to cortisol by 11β-hydroxysteroid dehydrogenase type 1 (11βHSD1) in the endoplasmic reticulum (ER) of the target cells is a major determinant of glucocorticoid action, and plays an important role in the development of obesity-related diseases. Inhibition of 11βHSD1 activity is, therefore, considered as a promising novel strategy for the treatment of metabolic syndrome and diabetes. Tea flavanols and their major representative, epigallocatechin gallate are known as antiobesity and antidiabetic agents. Their impacts on blood glucose level, hepatic glucose production, and insulin responsiveness resemble those observed on inhibition or depletion of 11βHSD1. We aimed to study the effect of epigallocatechin gallate on 11βHSD1 activity in ER-derived rat liver microsomes by measuring cortisone and cortisol with HPLC. Cortisol production was efficiently suppressed in a concentration dependent manner in intact microsomal vesicles. However, this effect was abolished by membrane permeabilization; and the three proteins involved in the overall process (11βHSD1, hexose 6-phosphate dehydrogenase, and glucose 6-phosphate transporter) were not or only mildly affected. Further investigation revealed the oxidation of luminal NADPH to NADP⁺, which attenuates cortisone reduction and favors cortisol oxidation in this compartment. Such a redox shift in the ER lumen might contribute to the beneficial health effects of tea flavanols and should be regarded as a promising strategy for the development of novel selective 11βHSD1 inhibitors to treat obesity-related diseases.

  9. Flavonol content, oil %, and fatty acid composition variability in seeds of Teramnus labialis and T. uncinatus accessions with nutraceutical potential

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Teramnus labialis and T. uncinatus are both underutilized legume species. Teramnus labialis is used as food in India while T. uncinatus has potential use in pasture mixes. Photoperiod-sensitive Teramnus accessions were grown in the greenhouse from 2010 to 2011 and evaluated for flavonol content, oil...

  10. Redox interplay between mitochondria and peroxisomes

    PubMed Central

    Lismont, Celien; Nordgren, Marcus; Van Veldhoven, Paul P.; Fransen, Marc

    2015-01-01

    Reduction-oxidation or “redox” reactions are an integral part of a broad range of cellular processes such as gene expression, energy metabolism, protein import and folding, and autophagy. As many of these processes are intimately linked with cell fate decisions, transient or chronic changes in cellular redox equilibrium are likely to contribute to the initiation and progression of a plethora of human diseases. Since a long time, it is known that mitochondria are major players in redox regulation and signaling. More recently, it has become clear that also peroxisomes have the capacity to impact redox-linked physiological processes. To serve this function, peroxisomes cooperate with other organelles, including mitochondria. This review provides a comprehensive picture of what is currently known about the redox interplay between mitochondria and peroxisomes in mammals. We first outline the pro- and antioxidant systems of both organelles and how they may function as redox signaling nodes. Next, we critically review and discuss emerging evidence that peroxisomes and mitochondria share an intricate redox-sensitive relationship and cooperate in cell fate decisions. Key issues include possible physiological roles, messengers, and mechanisms. We also provide examples of how data mining of publicly-available datasets from “omics” technologies can be a powerful means to gain additional insights into potential redox signaling pathways between peroxisomes and mitochondria. Finally, we highlight the need for more studies that seek to clarify the mechanisms of how mitochondria may act as dynamic receivers, integrators, and transmitters of peroxisome-derived mediators of oxidative stress. The outcome of such studies may open up exciting new avenues for the community of researchers working on cellular responses to organelle-derived oxidative stress, a research field in which the role of peroxisomes is currently highly underestimated and an issue of discussion. PMID:26075204

  11. 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

  12. Using a Simultaneous Prompting Procedure to Embed Core Content When Teaching a Potential Employment Skill

    ERIC Educational Resources Information Center

    Collins, Belva C.; Terrell, Misty; Test, David W.

    2017-01-01

    This investigation used a multiple-probe-across-participants design to examine the effects of using a simultaneous prompting procedure to teach four secondary students with mild intellectual disabilities the employment task of caring for plants in a greenhouse. The instructor also embedded photosynthesis science content as nontargeted information…

  13. Potential to alter the content and composition of milk fat through nutrition.

    PubMed

    Ashes, J R; Gulati, S K; Scott, T W

    1997-09-01

    Nutritional manipulation of the rumen ecosystem provides a strategy to alter the content and composition of milk fat. Dietary fat supplements affect the content and composition of milk fat. The magnitude of changes is influenced by the degree of protection; as protection increases, the deleterious effects fatty acids on microbial activity decreases, and biohydrogenation of C18 unsaturated fatty acids is reduced. In addition, change is influenced by the transfer of dietary fat into milk, which is related to fatty acid composition, degree of ruminal metabolism, and efficiency of digestion. A cascade of metabolic events involving specific nutrients (e.g., trans fatty acids and cyclopropene acids) occurs that regulates the activity of key enzymes in pathways of endogenous fat synthesis within the mammary gland. When cattle are fed oilseeds (e.g., canola and cotton) with > 75% protection from biohydrogenation, the proportion of saturated to unsaturated fatty acids is changed, and the fat content of milk is increased. Human consumption of dairy products containing elevated proportions of C18 mono- and polyunsaturated fatty acids reduces the content of cholesterol in plasma low density lipoproteins. These fat-modified dairy products are more susceptible to autoxidation, which can be controlled by including vitamin E in the diet of lactating cow. These products also have much less solid fat, which improves spreadability of butter. By protecting different oilseeds from ruminal metabolism, demands for energy can be satisfied while producing milk fat that can be designed for consumer and manufacturing requirements.

  14. Cobalt(II), nickel(II) and copper(II) complexes of a hexadentate pyridine amide ligand. Effect of donor atom (ether vs. thioether) on coordination geometry, spin-state of cobalt and M(III)-M(II) redox potential.

    PubMed

    Pandey, Sharmila; Das, Partha Pratim; Singh, Akhilesh Kumar; Mukherjee, Rabindranath

    2011-10-28

    Using an acyclic hexadentate pyridine amide ligand, containing a -OCH(2)CH(2)O- spacer between two pyridine-2-carboxamide units (1,4-bis[o-(pyrydine-2-carboxamidophenyl)]-1,4-dioxabutane (H(2)L(9)), in its deprotonated form), four new complexes, [Co(II)(L(9))] (1) and its one-electron oxidized counterpart [Co(III)(L(9))][NO(3)]·2H(2)O (2), [Ni(II)(L(9))] (3) and [Cu(II)(L(9))] (4), have been synthesized. Structural analyses revealed that the Co(II) centre in 1 and the Ni(II) centre in 3 are six-coordinate, utilizing all the available donor sites and the Cu(II) centre in 4 is effectively five-coordinated (one of the ether O atoms does not participate in coordination). The structural parameters associated with the change in the metal coordination environment have been compared with corresponding complexes of thioether-containing hexadentate ligands. The μ(eff) values at 298 K of 1-4 correspond to S = 3/2, S = 0, S = 1 and S = 1/2, respectively. Absorption spectra for all the complexes have been investigated. EPR spectral properties of the copper(II) complex 4 have been investigated, simulated and analyzed. Cyclic voltammetric experiments in CH(2)Cl(2) reveal quasireversible Co(III)-Co(II), Ni(III)-Ni(II) and Cu(II)-Cu(I) redox processes. In going from ether O to thioether S coordination, the effect of the metal coordination environment on the redox potential values of Co(III)-Co(II) (here the effect of spin-state as well), Ni(III)-Ni(II) and Cu(II)-Cu(I) processes have been systematically analyzed.

  15. Redox enzyme-mimicking activities of CeO2 nanostructures: Intrinsic influence of exposed facets.

    PubMed

    Yang, Yushi; Mao, Zhou; Huang, Wenjie; Liu, Lihua; Li, Junli; Li, Jialiang; Wu, Qingzhi

    2016-10-17

    CeO2 nanoparticles (NPs) have been well demonstrated as an antioxidant in protecting against oxidative stress-induced cellular damages and a potential therapeutic agent for various diseases thanks to their redox enzyme-mimicking activities. The Ce(3+)/Ce(4+) ratio and oxygen vacancies on the surface have been considered as the major originations responsible for the redox enzyme-mimicking activities of CeO2 NPs. Herein, CeO2 nanostructures (nanocubes and nanorods) exposed different facets were synthesized via a facile hydrothermal method. The characterizations by X-ray photoelectron spectroscopy, Raman spectroscopy, and UV-Vis spectroscopy show that the Ce(3+)/Ce(4+) ratio and oxygen vacancy content on the surfaces of as-synthesized CeO2 nanostructures are nearly at the same levels. Meanwhile, the enzymatic activity measurements indicate that the redox enzyme-mimicking activities of as-synthesized CeO2 nanostructures are greatly dependent on their exposed facets. CeO2 nanocubes with exposed {100} facets exhibit a higher peroxidase but lower superoxide dismutase activity than those of the CeO2 nanorods with exposed {110} facets. Our results provide new insights into the redox enzyme-mimicking activities of CeO2 nanostructures, as well as the design and synthesis of inorganic nanomaterials-based artificial enzymes.

  16. Redox enzyme-mimicking activities of CeO2 nanostructures: Intrinsic influence of exposed facets

    NASA Astrophysics Data System (ADS)

    Yang, Yushi; Mao, Zhou; Huang, Wenjie; Liu, Lihua; Li, Junli; Li, Jialiang; Wu, Qingzhi

    2016-10-01

    CeO2 nanoparticles (NPs) have been well demonstrated as an antioxidant in protecting against oxidative stress-induced cellular damages and a potential therapeutic agent for various diseases thanks to their redox enzyme-mimicking activities. The Ce3+/Ce4+ ratio and oxygen vacancies on the surface have been considered as the major originations responsible for the redox enzyme-mimicking activities of CeO2 NPs. Herein, CeO2 nanostructures (nanocubes and nanorods) exposed different facets were synthesized via a facile hydrothermal method. The characterizations by X-ray photoelectron spectroscopy, Raman spectroscopy, and UV-Vis spectroscopy show that the Ce3+/Ce4+ ratio and oxygen vacancy content on the surfaces of as-synthesized CeO2 nanostructures are nearly at the same levels. Meanwhile, the enzymatic activity measurements indicate that the redox enzyme-mimicking activities of as-synthesized CeO2 nanostructures are greatly dependent on their exposed facets. CeO2 nanocubes with exposed {100} facets exhibit a higher peroxidase but lower superoxide dismutase activity than those of the CeO2 nanorods with exposed {110} facets. Our results provide new insights into the redox enzyme-mimicking activities of CeO2 nanostructures, as well as the design and synthesis of inorganic nanomaterials-based artificial enzymes.

  17. Redox enzyme-mimicking activities of CeO2 nanostructures: Intrinsic influence of exposed facets

    PubMed Central

    Yang, Yushi; Mao, Zhou; Huang, Wenjie; Liu, Lihua; Li, Junli; Li, Jialiang; Wu, Qingzhi

    2016-01-01

    CeO2 nanoparticles (NPs) have been well demonstrated as an antioxidant in protecting against oxidative stress-induced cellular damages and a potential therapeutic agent for various diseases thanks to their redox enzyme-mimicking activities. The Ce3+/Ce4+ ratio and oxygen vacancies on the surface have been considered as the major originations responsible for the redox enzyme-mimicking activities of CeO2 NPs. Herein, CeO2 nanostructures (nanocubes and nanorods) exposed different facets were synthesized via a facile hydrothermal method. The characterizations by X-ray photoelectron spectroscopy, Raman spectroscopy, and UV-Vis spectroscopy show that the Ce3+/Ce4+ ratio and oxygen vacancy content on the surfaces of as-synthesized CeO2 nanostructures are nearly at the same levels. Meanwhile, the enzymatic activity measurements indicate that the redox enzyme-mimicking activities of as-synthesized CeO2 nanostructures are greatly dependent on their exposed facets. CeO2 nanocubes with exposed {100} facets exhibit a higher peroxidase but lower superoxide dismutase activity than those of the CeO2 nanorods with exposed {110} facets. Our results provide new insights into the redox enzyme-mimicking activities of CeO2 nanostructures, as well as the design and synthesis of inorganic nanomaterials-based artificial enzymes. PMID:27748403

  18. Effect of mesocelluar carbon foam electrode material on performance of vanadium redox flow battery

    NASA Astrophysics Data System (ADS)

    Jeong, Sanghyun; An, Sunhyung; Jeong, Jooyoung; Lee, Jinwoo; Kwon, Yongchai

    2015-03-01

    Languid reaction rate of VO2+/VO2+ redox couple is a problem to solve for improving performance of vanadium redox flow battery (VRFB). To facilitate the slow reaction materials including large pore sized mesocellular carbon foam (MSU-F-C and Pt/MSU-F-C) are used as new catalyst. Their catalytic activity and reaction reversibility are estimated and compared with other catalysts, while cycle tests of charge-discharge and polarization curve tests are implemented to evaluate energy efficiency (EE) and maximum power density (MPD). Their crystal structure, specific surface area and catalyst morphology are measured by XRD, BET and TEM. The new catalysts indicate high peak current ratio, small peak potential difference and high electron transfer rate constant, proving that their catalytic activity and reaction reversibility are superior. Regarding the charge-discharge and polarization curve tests, the VRFB single cells including new catalysts show high EE as well as low overpotential and internal resistance and high MPD. Such excellent results are due to mostly unique characteristics of MSU-F-C having large interconnected mesopores, high surface area and large contents of hydroxyl groups that serve as active sites for VO2+/VO2+ redox reaction and platinums (Pts) supporting the MSU-F-C. Indeed, employment of the catalysts including MSU-F-C leads to enhancement in performance of VRFB by facilitating the slow VO2+/VO2+ redox reaction.

  19. 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.

  20. 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

  1. Carbon Redox-Polymer-Gel Hybrid Supercapacitors

    NASA Astrophysics Data System (ADS)

    Vlad, A.; Singh, N.; Melinte, S.; Gohy, J.-F.; Ajayan, P. M.

    2016-02-01

    Energy storage devices that provide high specific power without compromising on specific energy are highly desirable for many electric-powered applications. Here, we demonstrate that polymer organic radical gel materials support fast bulk-redox charge storage, commensurate to surface double layer ion exchange at carbon electrodes. When integrated with a carbon-based electrical double layer capacitor, nearly ideal electrode properties such as high electrical and ionic conductivity, fast bulk redox and surface charge storage as well as excellent cycling stability are attained. Such hybrid carbon redox-polymer-gel electrodes support unprecedented discharge rate of 1,000C with 50% of the nominal capacity delivered in less than 2 seconds. Devices made with such electrodes hold the potential for battery-scale energy storage while attaining supercapacitor-like power performances.

  2. Redox Reactivity of Cerium Oxide Nanoparticles Induces the Formation of Disulfide Bridges in Thiol-Containing Biomolecules.

    PubMed

    Rollin-Genetet, Françoise; Seidel, Caroline; Artells, Ester; Auffan, Mélanie; Thiéry, Alain; Vidaud, Claude

    2015-12-21

    The redox state of disulfide bonds is implicated in many redox control systems, such as the cysteine-cystine couple. Among proteins, ubiquitous cysteine-rich metallothioneins possess thiolate metal binding groups susceptible to metal exchange in detoxification processes. CeO2 NPs are commonly used in various industrial applications due to their redox properties. These redox properties that enable dual oxidation states (Ce(IV)/Ce(III)) to exist at their surface may act as oxidants for biomolecules. The interaction among metallothioneins, cysteine, and CeO2 NPs was investigated through various biophysical approaches to shed light on the potential effects of the Ce(4+)/Ce(3+) redox system on the thiol groups of these biomolecules. The possible reaction mechanisms include the formation of a disulfide bridge/Ce(III) complex resulting from the interaction between Ce(IV) and the thiol groups, leading to metal unloading from the MTs, depending on their metal content and cluster type. The formation of stable Ce(3+) disulfide complexes has been demonstrated via their fluorescence properties. This work provides the first evidence of thiol concentration-dependent catalytic oxidation mechanisms between pristine CeO2 NPs and thiol-containing biomolecules.

  3. 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.

  4. Potential yields and properties of oil from the hydrothermal liquefaction of microalgae with different biochemical content.

    PubMed

    Biller, P; Ross, A B

    2011-01-01

    A range of model biochemical components, microalgae and cyanobacteria with different biochemical contents have been liquefied under hydrothermal conditions at 350 °C, ∼200 bar in water, 1M Na(2)CO(3) and 1M formic acid. The model compounds include albumin and a soya protein, starch and glucose, the triglyceride from sunflower oil and two amino acids. Microalgae include Chlorella vulgaris,Nannochloropsis occulata and Porphyridium cruentum and the cyanobacteria Spirulina. The yields and product distribution obtained for each model compound have been used to predict the behaviour of microalgae with different biochemical composition and have been validated using microalgae and cyanobacteria. Broad agreement is reached between predictive yields and actual yields for the microalgae based on their biochemical composition. The yields of bio-crude are 5-25 wt.% higher than the lipid content of the algae depending upon biochemical composition. The yields of bio-crude follow the trend lipids>proteins>carbohydrates.

  5. Deuterium content of water increases depression susceptibility: the potential role of a serotonin-related mechanism.

    PubMed

    Strekalova, Tatyana; Evans, Matthew; Chernopiatko, Anton; Couch, Yvonne; Costa-Nunes, João; Cespuglio, Raymond; Chesson, Lesley; Vignisse, Julie; Steinbusch, Harry W; Anthony, Daniel C; Pomytkin, Igor; Lesch, Klaus-Peter

    2015-01-15

    Environmental factors can significantly affect disease prevalence, including neuropsychiatric disorders such as depression. The ratio of deuterium to protium in water shows substantial geographical variation, which could affect disease susceptibility. Thus the link between deuterium content of water and depression was investigated, both epidemiologically, and in a mouse model of chronic mild stress. We performed a correlation analysis between deuterium content of tap water and rates of depression in regions of the USA. Next, we used a 10-day chronic stress paradigm to test whether 2-week deuterium-depleted water treatment (91 ppm) affects depressive-like behavior and hippocampal SERT. The effect of deuterium-depletion on sleep electrophysiology was also evaluated in naïve mice. There was a geographic correlation between a content of deuterium and the prevalence of depression across the USA. In the chronic stress model, depressive-like features were reduced in mice fed with deuterium-depleted water, and SERT expression was decreased in mice treated with deuterium-treated water compared with regular water. Five days of predator stress also suppressed proliferation in the dentate gyrus; this effect was attenuated in mice fed with deuterium-depleted water. Finally, in naïve mice, deuterium-depleted water treatment increased EEG indices of wakefulness, and decreased duration of REM sleep, phenomena that have been shown to result from the administration of selective serotonin reuptake inhibitors (SSRI). Our data suggest that the deuterium content of water may influence the incidence of affective disorder-related pathophysiology and major depression, which might be mediated by the serotoninergic mechanisms.

  6. Establishing safe and potentially efficacious fortification contents for folic acid and vitamin B12.

    PubMed

    Dary, Omar

    2008-06-01

    Determining the micronutrient contents infortified foods depends not only on the health goal (additional intake to complement the diet), but also on ensuring that fortification does not raise micronutrient intakes beyond the Tolerable Upper Intake Level (UL), i.e., the safe limit. Technological incompatibility and cost may also restrict the fortification contents. For folic acid, the limiting factor is safety, while for vitamin B12, it is cost. However, adequate fortification contents that are both safe and efficacious can be estimated for both nutrients. In order to obtain the maximum benefit from the fortification programs, three different formulas responding to three categories of consumption, as specified by the median and 95th percentile of consumption, are proposed. The model presented is based on the estimation of a Feasible Fortification Level (FFL), which then is used to determine the average, minimum, and maximum contents of the nutrients during production, taking into consideration the acceptable variation of the fortification process. Finally, the regulatory parameters, which support standards and enforcement, are calculated by reducing the proportion of the nutrient that is degraded during the usual marketing process of the fortified food. It is expected that this model will establish a common standard for food fortification, and improve the reliability and enforcement procedures of these programs. The model was applied to flours as vehicles for folic acid in the United States, Guatemala, and Chile. Analysis of the data revealed that, with the exception of Chile, where wheat flour consumption is very high and probably within a narrow range, supplementation with folic acid is still needed to cover individuals at the low end of consumption. This is especially true when the difference in flour consumption is too wide, as in the case of Guatemala, where the proportional difference between consumption at the 95th percentile of the nonpoor group is as high

  7. Redox regulation of cardiac hypertrophy.

    PubMed

    Sag, Can M; Santos, Celio X C; Shah, Ajay M

    2014-08-01

    It is increasingly evident that redox-dependent modifications in cellular proteins and signaling pathways (or redox signaling) play important roles in many aspects of cardiac hypertrophy. Indeed, these redox modifications may be intricately linked with the process of hypertrophy wherein there is not only a significant increase in myocardial O2 consumption but also important alterations in metabolic processes and in the local generation of O2-derived reactive species (ROS) that modulate and/or amplify cell signaling pathways. This article reviews our current knowledge of redox signaling pathways and their roles in cardiac hypertrophy. This article is part of a Special Issue entitled "Redox Signalling in the Cardiovascular System".

  8. Microfluidic redox battery.

    PubMed

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

    2013-07-07

    A miniaturized microfluidic battery is proposed, which is the first membraneless redox battery demonstrated to date. This unique concept capitalizes on dual-pass flow-through porous electrodes combined with stratified, co-laminar flow to generate electrical power on-chip. The fluidic design is symmetric to allow for both charging and discharging operations in forward, reverse, and recirculation modes. The proof-of-concept device fabricated using low-cost materials integrated in a microfluidic chip is shown to produce competitive power levels when operated on a vanadium redox electrolyte. A complete charge/discharge cycle is performed to demonstrate its operation as a rechargeable battery, which is an important step towards providing sustainable power to lab-on-a-chip and microelectronic applications.

  9. Redox regulation of cancer metastasis: molecular signaling and therapeutic opportunities.

    PubMed

    Yang, Wenyong; Zou, Linzhi; Huang, Canhua; Lei, Yunlong

    2014-08-01

    Cancer metastasis is the major cause of cancer-related mortality. Accumulated evidence has shown that high-metastasis potential cancer cells have more reactive oxygen species (ROS) accumulation compared with low-metastasis potential cancer cells. ROS can function as second messengers to regulate multiple cancer metastasis-related signaling pathways via reversible oxidative posttranslational modifications of cysteine in key redox-sensitive proteins, which leads to the structural and functional change of these proteins. Because ROS can promote cancer metastasis, therapeutic strategies aiming at inducing/reducing cellular ROS level or targeting redox sensors involved in metastasis hold great potential in developing new efficient approaches for anticancer therapy. In this review, we summarize recent findings on regulation of tumor metastasis by key redox sensors and describe the potential of targeting redox signaling pathways for cancer therapy.

  10. Human health and ecological toxicity potentials due to heavy metal content in waste electronic devices with flat panel displays.

    PubMed

    Lim, Seong-Rin; Schoenung, Julie M

    2010-05-15

    Display devices such as cathode-ray tube (CRT) televisions and computer monitors are known to contain toxic substances and have consequently been banned from disposal in landfills in the State of California and elsewhere. New types of flat panel display (FPD) devices, millions of which are now purchased each year, also contain toxic substances, but have not previously been systematically studied and compared to assess the potential impact that could result from their ultimate disposal. In the current work, the focus is on the evaluation of end-of-life toxicity potential from the heavy metal content in select FPD devices with the intent to inform material selection and design-for-environment (DfE) decisions. Specifically, the metals antimony, arsenic, barium, beryllium, cadmium, chromium, cobalt, copper, lead, mercury, molybdenum, nickel, selenium, silver, vanadium, and zinc in plasma TVs, LCD (liquid crystal display) TVs, LCD computer monitors and laptop computers are considered. The human health and ecotoxicity potentials are evaluated through a life cycle assessment perspective by combining data on the respective heavy metal contents, the characterization factors in the U.S. EPA Tool for the Reduction and Assessment of Chemical and other environmental Impacts (TRACI), and a pathway and impact model. Principal contributors to the toxicity potentials are lead, arsenic, copper, and mercury. Although the heavy metal content in newer flat panel display devices creates less human health toxicity potential than that in CRTs, for ecological toxicity, the new devices are worse, especially because of the mercury in LCD TVs and the copper in plasma TVs.

  11. 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.

  12. Temporal moisture content variability beneath and external to a building and the potential effects on vapor intrusion risk assessment.

    PubMed

    Tillman, Fred D; Weaver, James W

    2007-06-15

    Migration of vapors from organic chemicals residing in the subsurface into overlying buildings is known as vapor intrusion. Because of the difficulty in evaluating vapor intrusion by indoor air sampling, models are often employed to determine if a potential indoor inhalation exposure pathway exists and, if such a pathway is complete, whether long-term exposure increases the occupants' risk for cancer or other toxic effects to an unacceptable level. For site-specific vapor intrusion assessments, moisture content is, at times, determined from soil cores taken in open spaces between buildings. However, there is little published information on how moisture content measured outside a building structure compares with the moisture content directly beneath the building - where the values are most critical for vapor intrusion assessments. This research begins to address these issues by investigating the movement of soil moisture next to and beneath a building at a contaminated field site and determining the effect on vapor intrusion risk assessment. A two-dimensional, variably-saturated water flow model, HYDRUS-2D, is used with 2 years of hourly, local rainfall data to simulate subsurface moisture content in the vicinity of a hypothetical 10 x 10-m building slab at a contaminated field site. These moisture content values are used in vapor intrusion risk assessment simulations using the Johnson and Ettinger model with instantaneous and averaged moisture contents. Results show that vapor intrusion risk assessments based on moisture content determined from soil cores taken external to a building structure may moderately-to-severely underestimate the vapor intrusion risk from beneath the structure. Soil under the edges of a slab may be influenced by rainfall events and may show reduced vapor intrusion risk as a consequence. Data from a building instrumented with subslab moisture probes showed results similar to the modeling, but with a smaller difference between the subslab and

  13. Rare earth elements and critical metal content of extracted landfilled material and potential recovery opportunities.

    PubMed

    Gutiérrez-Gutiérrez, Silvia C; Coulon, Frédéric; Jiang, Ying; Wagland, Stuart

    2015-08-01

    Rare earth elements (REEs), Platinum group metals (PGMs) and other critical metals currently attract significant interest due to the high risks of supply shortage and substantial impact on the economy. Their uses in many applications have made them present in municipal solid waste (MSW) and in commercial and industrial waste (C&I), since several industrial processes produce by-products with high content of these metals. With over 4000 landfills in the UK alone, the aim of this study was to assess the existence of these critical metals within landfills. Samples collected from four closed landfills in UK were subjected to a two-step acid digestion to extract 27 metals of interest. Concentrations across the four landfill sites were 58±6mgkg(-1) for REEs comprising 44±8mgkg(-1) for light REEs, 11±2mgkg(-1) for heavy REEs and 3±1mgkg(-1) for Scandium (Sc) and 3±1.0mgkg(-1) of PGMs. Compared to the typical concentration in ores, these concentrations are too low to achieve a commercially viable extraction. However, content of other highly valuable metals (Al and Cu) was found in concentrations equating to a combined value across the four landfills of around $400 million, which increases the economic viability of landfill mining. Presence of critical metals will mainly depend on the type of waste that was buried but the recovery of these metals through landfill mining is possible and is economically feasible only if additional materials (plastics, paper, metallic items and other) are also recovered for reprocessing.

  14. Potential risk and sodium content of children's ready-to-eat foods distributed at major amusement parks in Korea.

    PubMed

    Lee, N-Y; Park, S-Y; Lee, Y-M; Choi, S-Y; Jeong, S-H; Chung, M-S; Chang, Y-S; Choi, S-H; Bae, D-H; Ha, S-D

    2013-01-01

    This study was conducted to help better understand the current sodium intake of Korean children and to establish children's good eating habits through investigation of the sodium content of ready-to-eat foods collected from nine major amusement parks in Korea. The sodium content of a total of 322 products was analysed by using ICP and then the potential risk based on the recommended daily intake of sodium as described in the Korean dietary reference intakes was determined. The results showed that sodium content was the lowest in muffins (245 mg/100 g) and the highest in seasoned dried filefish (1825 mg/100 g). The average amounts of sodium per serving of seasoned dried filefish, tteokbokki and fish paste were 1150, 1248 and 1097 mg, respectively. The values were above 50% of the daily intake of sodium recommended by the Korean dietary reference intake. The ready-to-eat foods were also classified into high, medium and low sodium content on the basis of standards recommended by the Korean Food and Drug Administration. Most snacks were classified as high sodium foods because they exceeded "300 mg (84.5% of the total daily allowance)". Furthermore, the meal substitution foods such as kimbab, tteokbokki, mandus, sandwiches and hamburgers exceeded "600 mg (90.3% of the total daily allowance)" and were also classified as high sodium foods. In addition, ready-to-eat foods in amusement parks are similar to foods eaten on streets and foods around school zones, which contain high sodium content; thus, the intake frequency might be high, which would induce high risk to children health. Koreans already consume a high amount of sodium daily via their usual diets. So, the sodium content in snacks and substitution foods needs to be reduced. Consequently, this study noted that parents and guardians should carefully consider their children's consumption of ready-to-eat foods from Korean amusement parks.

  15. The Potential of a High Protein-Low Carbohydrate Diet to Preserve Intrahepatic Triglyceride Content in Healthy Humans

    PubMed Central

    Martens, Eveline A.; Gatta-Cherifi, Blandine; Gonnissen, Hanne K.; Westerterp-Plantenga, Margriet S.

    2014-01-01

    Background Protein supplementation has been shown to reduce the increases in intrahepatic triglyceride (IHTG) content induced by acute hypercaloric high-fat and high-fructose diets in humans. Objective To assess the effect of a 12-wk iso-energetic high protein-low carbohydrate (HPLC) diet compared with an iso-energetic high carbohydrate-low protein (HCLP) diet on IHTG content in healthy non-obese subjects, at a constant body weight. Design Seven men and nine women [mean ± SD age: 24±5 y; BMI: 22.9±2.1 kg/m2] were randomly allocated to a HPLC [30/35/35% of energy (En%) from protein/carbohydrate/fat] or a HCLP (5/60/35 En%) diet by stratification on sex, age and BMI. Dietary guidelines were prescribed based on individual daily energy requirements. IHTG content was measured by 1H-magnetic resonance spectroscopy before and after the dietary intervention. Results IHTG content changed in different directions with the HPLC (CH2H2O: 0.23±0.17 to 0.20±0.10; IHTG%: 0.25±0.20% to 0.22±0.11%) compared with the HCLP diet (CH2H2O: 0.34±0.20 vs. 0.38±0.21; IHTG%: 0.38±0.22% vs. 0.43±0.24%), which resulted in a lower IHTG content in the HPLC compared with the HCLP diet group after 12 weeks, which almost reached statistical significance (P = 0.055). Conclusions A HPLC vs. a HCLP diet has the potential to preserve vs. enlarge IHTG content in healthy non-obese subjects at a constant body weight. Trial Registration Clinicaltrials.gov NCT01551238 PMID:25330327

  16. High-Content Imaging Assays for Identifying Compounds that Generate Superoxide and Impair Mitochondrial Membrane Potential in Adherent Eukaryotic Cells.

    PubMed

    Billis, Puja; Will, Yvonne; Nadanaciva, Sashi

    2014-02-19

    Reactive oxygen species (ROS) are constantly produced in cells as a result of aerobic metabolism. When there is an excessive production of ROS and the cell's antioxidant defenses are overwhelmed, oxidative stress occurs. The superoxide anion is a type of ROS that is produced primarily in mitochondria but is also generated in other regions of the cell including peroxisomes, endoplasmic reticulum, plasma membrane, and cytosol. Here, a high-content imaging assay using the dye dihydroethidium is described for identifying compounds that generate superoxide in eukaryotic cells. A high-content imaging assay using the fluorescent dye tetramethylrhodamine methyl ester is also described to identify compounds that impair mitochondrial membrane potential in eukaryotic cells. The purpose of performing both assays is to identify compounds that (1) generate superoxide at lower concentrations than they impair mitochondrial membrane potential, (2) impair mitochondrial membrane potential at lower concentrations than they generate superoxide, (3) generate superoxide and impair mitochondrial function at similar concentrations, and (4) do not generate superoxide or impair mitochondrial membrane potential during the duration of the assays.

  17. Rare earth elements and critical metal content of extracted landfilled material and potential recovery opportunities

    SciTech Connect

    Gutiérrez-Gutiérrez, Silvia C.; Coulon, Frédéric; Jiang, Ying; Wagland, Stuart

    2015-08-15

    Highlights: • Samples from multiple core drills were obtained from 4× landfill sites in the UK. • Each sample analysed for rare earth elements, critical metals and valuable metals. • Two stage microwave digestion method ensuring high yield. • High quantities of copper and aluminium were observed in the soil layers of landfill. • Across 4× landfills aluminium and copper present has a value of around $400 million. - Abstract: Rare earth elements (REEs), Platinum group metals (PGMs) and other critical metals currently attract significant interest due to the high risks of supply shortage and substantial impact on the economy. Their uses in many applications have made them present in municipal solid waste (MSW) and in commercial and industrial waste (C&I), since several industrial processes produce by-products with high content of these metals. With over 4000 landfills in the UK alone, the aim of this study was to assess the existence of these critical metals within landfills. Samples collected from four closed landfills in UK were subjected to a two-step acid digestion to extract 27 metals of interest. Concentrations across the four landfill sites were 58 ± 6 mg kg{sup −1} for REEs comprising 44 ± 8 mg kg{sup −1} for light REEs, 11 ± 2 mg kg{sup −1} for heavy REEs and 3 ± 1 mg kg{sup −1} for Scandium (Sc) and 3 ± 1.0 mg kg{sup −1} of PGMs. Compared to the typical concentration in ores, these concentrations are too low to achieve a commercially viable extraction. However, content of other highly valuable metals (Al and Cu) was found in concentrations equating to a combined value across the four landfills of around $400 million, which increases the economic viability of landfill mining. Presence of critical metals will mainly depend on the type of waste that was buried but the recovery of these metals through landfill mining is possible and is economically feasible only if additional materials (plastics, paper, metallic items and other) are

  18. Lead, cadmium and mercury contents and bioaccumulation potential of wild edible saprophytic and ectomycorrhizal mushrooms, Croatia.

    PubMed

    Širić, Ivan; Kasap, Ante; Bedeković, Dalibor; Falandysz, Jerzy

    2017-03-04

    Lead (Pb), cadmium (Cd), and mercury (Hg) contents in ten species of edible mushrooms in Trakošćan, Croatia were determined. In addition, the similarity between the studied species was determined by cluster analysis. The caps and stipes of the fruiting bodies were analysed separately. The analyses were carried out by inductively coupled plasma - optical emission spectrometry (ICP-OES). The greatest mean lead concentrations of 1.91 and 1.60 mg kg (-1) were determined in caps and stipes of Macrolepiota procera. The greatest mean concentrations of cadmium (3.23 and 2.24 mg kg(-1)) were determined in caps and stipes of Agaricus campestris and of mercury (2.56 and 2.35 mg kg(-1)) in Boletus edulis. In terms of the anatomical parts of the fruiting body (cap-stipe), a considerably greater concentration of the analysed elements was found in the cap for all mushroom species. According to calculated bio-concentration factors, all the examined species were found to be bio-accumulators of Cd and Hg. On the basis of the accumulation of the studied metals, great similarity of mushroom species belonging to the same genus and partial similarity of species of the same ecological affiliation was obtained by cluster analysis.

  19. Ecto-nucleotidases Activities in the Contents of Ovarian Endometriomas: Potential Biomarkers of Endometriosis

    PubMed Central

    Texidó, Laura; Romero, Claudia; García-Valero, José; Fernández Montoli, M. Eulalia; Baixeras, Núria; Condom, Enric; Ponce, Jordi; García-Tejedor, Amparo; Martín-Satué, Mireia

    2014-01-01

    Endometriosis, defined as the growth of endometrial tissue outside the uterus, is a common gynecologic condition affecting millions of women worldwide. It is an inflammatory, estrogen-dependent complex disorder, with broad symptomatic variability, pelvic pain, and infertility being the main characteristics. Ovarian endometriomas are frequently developed in women with endometriosis. Late diagnosis is one of the main problems of endometriosis; thus, it is important to identify biomarkers for early diagnosis. The aim of the present work is to evaluate the ecto-nucleotidases activities in the contents of endometriomas. These enzymes, through the regulation of extracellular ATP and adenosine levels, are key enzymes in inflammatory processes, and their expression has been previously characterized in human endometrium. To achieve our objective, the echo-guided aspirated fluids of endometriomas were analyzed by evaluating the ecto-nucleotidases activities and compared with simple cysts. Our results show that enzyme activities are quantifiable in the ovarian cysts aspirates and that endometriomas show significantly higher ecto-nucleotidases activities than simple cysts (5.5-fold increase for ATPase and 20-fold for ADPase), thus being possible candidates for new endometriosis biomarkers. Moreover, we demonstrate the presence of ecto-nucleotidases bearing exosomes in these fluids. These results add up to the knowledge of the physiopathologic mechanisms underlying endometriosis and, open up a promising new field of study. PMID:25276049

  20. Decadal potential predictability of upper ocean heat content over the twentieth century

    NASA Astrophysics Data System (ADS)

    Li, Shujun; Zhang, Liping; Wu, Lixin

    2017-02-01

    The statistical method, Average Predictability Time (APT) decomposition, is used in the present paper to estimate the decadal predictability of upper ocean heat content over the global ocean, North Pacific and North Atlantic, respectively. The twentieth century simulations from CMIP5 outputs are the main data sources in this study. On global scale, the leading predictable component is characterized by a warming trend over the majority of oceans, which is related to the anthropogenic forced response. The second predictable component has significant loadings in the North Atlantic, especially in the subtropical region, which originates from the Atlantic Multidecadal Oscillation (AMO) predictability. To separate interactions among different ocean basins, we further maximize APT in individual North Pacific and North Atlantic oceans. It is found that the second and the third predictable component in North Pacific are significantly correlated with the well-known North Pacific Gyre Oscillation mode and the Pacific Decadal Oscillation respectively. Upper limit prediction skill of these two components are on the order of 6 years. In contrast, the most predictable component derived from the North Atlantic features an AMO-like spatial structure with its prediction skill up to 18 years, while the basin mode due to global warming only exists as the third component. This indicates the interdecadal variability in the North Atlantic is strong enough to mask the anthropogenic climate signals. Furthermore, predictability in the real world is also investigated and compared with model results by using observation-based data.

  1. Experimental and Computational Analysis of the Solvent-Dependent O2/Li(+)-O2(-) Redox Couple: Standard Potentials, Coupling Strength, and Implications for Lithium-Oxygen Batteries.

    PubMed

    Kwabi, David G; Bryantsev, Vyacheslav S; Batcho, Thomas P; Itkis, Daniil M; Thompson, Carl V; Shao-Horn, Yang

    2016-02-24

    Understanding and controlling the kinetics of O2 reduction in the presence of Li(+)-containing aprotic solvents, to either Li(+)-O2(-) by one-electron reduction or Li2 O2 by two-electron reduction, is instrumental to enhance the discharge voltage and capacity of aprotic Li-O2 batteries. Standard potentials of O2 /Li(+)-O2(-) and O2/O2(-) were experimentally measured and computed using a mixed cluster-continuum model of ion solvation. Increasing combined solvation of Li(+) and O2(-) was found to lower the coupling of Li(+)-O2(-) and the difference between O2/Li(+)-O2(-) and O2/O2(-) potentials. The solvation energy of Li(+) trended with donor number (DN), and varied greater than that of O2 (-) ions, which correlated with acceptor number (AN), explaining a previously reported correlation between Li(+)-O2(-) solubility and DN. These results highlight the importance of the interplay between ion-solvent and ion-ion interactions for manipulating the energetics of intermediate species produced in aprotic metal-oxygen batteries.

  2. Ciprofloxacin provokes SOS-dependent changes in respiration and membrane potential and causes alterations in the redox status of Escherichia coli.

    PubMed

    Smirnova, Galina V; Tyulenev, Aleksey V; Muzyka, Nadezda G; Peters, Mikhail A; Oktyabrsky, Oleg N

    2017-01-01

    An in-depth understanding of the physiological response of bacteria to antibiotic-induced stress is needed for development of new approaches to combatting microbial infections. Fluoroquinolone ciprofloxacin causes phase alterations in Escherichia coli respiration and membrane potential that strongly depend on its concentration. Concentrations lower than the optimal bactericidal concentration (OBC) do not inhibit respiration during the first phase. A dose higher than the OBC provokes immediate SOS-independent inhibition of respiration and growth that can contribute to a decreased SOS response and lowered susceptibility to high concentrations of ciprofloxacin. Cells retain their metabolic activity, membrane potential and accelerated K(+) uptake and produce low levels of superoxide and H2O2 during the first phase. The time before initiation of the second phase is inversely correlated with the ciprofloxacin concentration. The second phase is SOS-dependent and characterized by respiratory inhibition, membrane depolarization, K(+) and glutathione leakage and cessation of glucose consumption and may be considered as cell death. atpA, gshA and kefBkefC knockouts, which perturb fluxes of protons and K(+), can modify the degree and duration of respiratory inhibition and potassium retention. Loss of K(+) efflux channels KefB and KefC enhances the susceptibility of E. coli to ciprofloxacin.

  3. Probing the mechanism of hypoxia selectivity of copper bis(thiosemicarbazonato) complexes: DFT calculation of redox potentials and absolute acidities in solution.

    PubMed

    Holland, Jason P; Green, Jennifer C; Dilworth, Jonathan R

    2006-02-14

    Density functional theory (DFT) calculations have been performed using the uB3LYP/6-31++G(d,p) model to calculate the solution phase one-electron reduction potentials (E(calc)) and absolute pKa values of a series of copper bis(thiosemicarbazonato) complexes. The effects of solvation in water and dimethylsulfoxide (DMSO) are incorporated as a self-consistent reaction field (SCRF) using the integral equation formalism polarisable continuum model (IEFPCM) and are found to be essential for quantitative agreement with an average error in E(calc) of -0.02 V compared to experiment. The bonding and spin densities are examined through the use of Natural Bond Order analysis and the results used to rationalise the calculated and observed reduction potentials. Calculated estimates of pKa values of several copper(II) species are presented and their implications for the mechanisms of transport and trapping within hypoxic cells are considered. Reduction is found to be a prerequisite for protonation of the complexes which suggests their transport in the blood stream as neutral species, and the mechanistic sequence is identified as a sequential electrochemical-chemical (EC) process. The complex equilibria of protonation, reoxidation and dissociation are discussed and the copper(I) diprotonated, cationic complex of diacetyl bis(4-methyl-3-thiosemicarbazonato)copper(II), Cu(I)ATSMH2(+), is identified as a possible candidate for the initial species trapped in hypoxic cells.

  4. Anaerobic digestion of fines from recovered paper processing - Influence of fiber source, lignin and ash content on biogas potential.

    PubMed

    Steffen, Friedrich; Requejo, Ana; Ewald, Christian; Janzon, Ron; Saake, Bodo

    2016-01-01

    Fines concentration harms paper machine runability and output quality in recovered paper processing, hence, their extraction would be fundamentally beneficial. In this study, separated fines from an industrial recycled fiber pulp (RFP) were characterized and evaluated for their potential biogas yields with a focus on understanding the role of varying lignin and ash contents. Further, these results were compared with biogas yields from conventional chemical and mechanical pulps. Overall, methane yields of fines from mechanical pulps (21-28mL/gVS) and RFP (127mL/gVS) are relatively low compared to the high methane yields of 375mL/gVS from the chemical pulp fines. However, it was shown that the high ash content in RFP fines (up to 50%) did not negatively influence overall yield, rather, it was the presence of slowly biodegrading lignin-rich fiber fines.

  5. Effect of Reducing Groundwater on the Retardation of Redox-Sensitive Radionuclides

    SciTech Connect

    Hu, Q; Zavarin, M; Rose, T P

    2008-04-21

    Laboratory batch sorption experiments were used to investigate variations in the retardation behavior of redox-sensitive radionuclides. Water-rock compositions used during these experiments were designed to simulate subsurface conditions at the Nevada Test Site (NTS), where a suite of radionuclides were deposited as a result of underground nuclear testing. Experimental redox conditions were controlled by varying the oxygen content inside an enclosed glove box and by adding reductants into the testing solutions. Under atmospheric (oxidizing) conditions, the radionuclide distribution coefficients varied with the mineralogical composition of the sorbent and the water chemistry. Under reducing conditions, distribution coefficients showed marked increases for {sup 99}Tc and {sup 237}Np in devitrified tuff, but much smaller variations in alluvium, carbonate rock, and zeolitic tuff. This effect was particularly important for {sup 99}Tc, which tends to be mobile under oxidizing conditions. Unlike other redox-sensitive radionuclides, iodine sorption may decrease under reducing conditions when I{sup -} is the predominant species. Overall, sorption of U to alluvium, devitrified tuff, and zeolitic tuff under atmospheric conditions was less than in the glove-box tests. However, the mildly reducing conditions achieved here were not likely to result in substantial U(VI) reduction to U(IV). Sorption of Pu was not affected by the decreasing redox conditions achieved in this study, as the predominant sorbed Pu species in all conditions was expected to be the low-solubility and strongly sorbing Pu(OH){sub 4}. Depending on the aquifer lithology, the occurrence of reducing conditions along a groundwater flowpath could potentially contribute to the retardation of redox-sensitive radionuclides {sup 99}Tc and {sup 237}Np, which are commonly identified as long-term dose contributors in the risk assessment in various nuclear facilities.

  6. Development of a Test Method to Determine Potential Peroxide Content in Turbine Fuels.

    DTIC Science & Technology

    1985-06-01

    reasonable time i.e., less than 48 hours. Through the generally accepted 43 C (110 F) bottle storage method fo accelerated fuel aging, the relative ratings of four selected fuels’ oxidative tendencies were established. A matrix of experiments was designed to allow selection of those short-term reaction conditions that would give results comparable to the 43 C bottle storage experiments. Additionally, the results of these experiments would allow the development of global reaction kinetics to aid the determination of fuel peroxidation potential. From a partially

  7. Redox Abnormalities as a Vulnerability Phenotype for Autism and Related Alterations in CNS Development

    DTIC Science & Technology

    2009-10-01

    systemic redox potential (GSH/GSSG; cysteine /cystine) reflects a vulnerability phenotype that is associated with regressive autism and is predictive of... acetylation /methylation that are reversible with treatment to restore redox potential. In Aim 1 we will determine whether redox potential in immune cells...900) and mouse tissue analysis for GSH/GSSG and cysteine /cystine. Ongoing; years 1.5-3). The preliminary results for the GSH/GSSG

  8. Antioxidant potential and its relationship with polyphenol content and degree of polymerization in Opuntia elatior Mill. fruits

    PubMed Central

    Itankar, Prakash R.; Sontakke, Varsha A.; Tauqeer, Mohd.; Charde, Sonal S.

    2014-01-01

    Background: Opuntia elatior Mill. (Nagaphani) fruits are traditionally recommended as an expectorant, remedy for whooping cough, asthma, gonorrhea, ulcers, tumors, in the treatment of diarrhea and syphilis. Many of these diseases are allied with oxidative stress caused by free radicals. Thus, current research is directed towards finding naturally-occurring antioxidants of plant origin. Aim: To evaluate antioxidant potential of hydro-alcoholic extract of the O. elatior fruits (HAOE) and its fractions. Materials and Methods: Using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and nitric oxide radical scavenging assay, total polyphenolic, flavonoid (FA), flavanone (FO) contents and degree of polymerization in relation with its antioxidant activity were examined. Results: The experimental data indicated that the HAOE, ethyl acetate (EAOE) and butanol (BFOE) soluble fractions have shown significant antioxidant activity. The highest polyphenolic, FA, FO contents and degree of polymerization were found in EAOE. The scavenging potential was in the order of Ascorbic Acid > EAOE > BFOE > HAOE > BIOE, where ascorbic acid was used as a positive control. The increased antioxidant potential of EAOE and BFOE fractions over HAOE extract may be attributed to the purification achieved by fractionation of the extract which in turn resulted in an increase in the degree of polymerization and segregation of secondary metabolites. Conclusion: The fruit of O. elatior can be used as the best alternative for synthetic antioxidants. PMID:26195906

  9. Measuring E(GSH) and H2O2 with roGFP2-based redox probes.

    PubMed

    Morgan, Bruce; Sobotta, Mirko C; Dick, Tobias P

    2011-12-01

    Redox biochemistry plays an important role in a wide range of cellular events. However, investigation of cellular redox processes is complicated by the large number of cellular redox couples, which are often not in equilibrium with one another and can vary significantly between subcellular compartments and cell types. Further, it is becoming increasingly clear that different redox systems convey different biological information; thus it makes little sense to talk of an overall "cellular redox state". To gain a more differentiated understanding of cellular redox biology, quantitative, redox couple-specific, in vivo measurements are necessary. Unfortunately our ability to investigate specific redox couples or redox-reactive molecules with the necessary degree of spatiotemporal resolution is very limited. The development of genetically encoded redox biosensors offers a promising new way to investigate redox biology. Recently developed redox-sensitive green fluorescent proteins (roGFPs), genetically fused to redox-active proteins, allow rapid equilibration of the roGFP moiety with a specific redox couple. Two probes based on this principle are now available: Grx1-roGFP2 for the measurement of glutathione redox potential (E(GSH)) and roGFP2-Orp1 for measuring changes in H(2)O(2) concentration. Here we provide a detailed protocol for the use of these probes in both yeast and mammalian systems using either plate-reader- or microscopy-based measurements.

  10. Study of Potential Sub-Micrometer-Thick Frost Events and Soil Water Content at Gale Crater

    NASA Astrophysics Data System (ADS)

    Martinez, G.; Fischer, E.; Renno, N. O.; De La Torre Juarez, M.; Meslin, P. Y.; Kemppinen, O.; Genzer, M.; Harri, A. M.; Ramos, M.; Borlina, C.; Schröder, S.; Gómez-Elvira, J.

    2014-12-01

    We analyze the highest confidence measurements of relative humidity [1] and ground temperature [2] to identify potential frost events at the surface of Gale Crater during the first 600 sols of the MSL mission. We find that between 4 and 6 am on sols 533, 535, 555, 557, 559 and 560 the ground temperature falls below the calculated frost point. Order-of-magnitude estimate for the thickness of the frost layer indicates that it is of the order of micrometers or less. Additionally, we analyze the relation between water vapor pressure and ground temperature to provide additional constraints on potential frost events and to quantify the exchange of adsorbed water between the surface and the atmosphere. Adsorbed water could be forced into liquid-like state at the of Gale because van der Waals forces between water ice molecules and mineral surfaces reduces the freezing point [3]. This form of liquid water is relevant to habitability because microorganisms could survive in liquid-like adsorbed water [4].References: [1] Harri, Ari-Matti et al., Mars Science Laboratory Relative Humidity Observations - Initial Results (2014), JGR (in press). [2] Martínez, G. M. et al., Surface Energy Budget and Thermal Inertia at Gale Crater: Calculations from Ground-Based Measurements (2014), JGR (in press). [3] Möhlmann, D., The influence of van der Waals forces on the state of water in the shallow subsurface of Mars (2008), Icarus 195 (1), 131-139. [4] Rivkina, E. M. et al., Metabolic activity of permafrost bacteria below the freezing point (2000), Appl. Environ. Microbiol., 66(8), 3230-3233.

  11. Crystal Structure and Biochemical Characterization of Chlamydomonas FDX2 Reveal Two Residues that, When Mutated, Partially Confer FDX2 the Redox Potential and Catalytic Properties of FDX1

    SciTech Connect

    Boehm, Marko; Alahuhta, Markus; Mulder, David W.; Peden, Erin A.; Long, Hai; Brunecky, Roman; Lunin, Vladimir V.; King, Paul W.; Ghirardi, Maria L.; Dubini, Alexandra

    2015-11-03

    The green alga Chlamydomonas reinhardtii contains six plastidic [2Fe2S]-cluster ferredoxins (FDXs), with FDX1 as the predominant isoform under photoautotrophic growth. FDX2 is highly similar to FDX1 and has been shown to interact with specific enzymes (such as nitrite reductase), as well as to share interactors with FDX1, such as the hydrogenases (HYDA), ferredoxin:NAD(P) reductase I (FNR1), and pyruvate:ferredoxin oxidoreductase (PFR1), albeit performing at low catalytic rates. Here we report the FDX2 crystal structure solved at 1.18 Å resolution. Based on differences between the Chlorella fusca FDX1 and C. reinhardtii FDX2 structures, we generated and purified point-mutated versions of the FDX2 protein and assayed them in vitro for their ability to catalyze hydrogen and NADPH photo-production. The data show that structural differences at two amino acid positions contribute to functional differences between FDX1 and FDX2, suggesting that FDX2 might have evolved from FDX1 toward a different physiological role in the cell. Moreover, we demonstrate that the mutations affect both the midpoint potentials of the FDX and kinetics of the FNR reaction, possibly due to altered binding between FDX and FNR. An effect on H2 photo-production rates was also observed, although the kinetics of the reaction were not further characterized.

  12. Crystal Structure and Biochemical Characterization of Chlamydomonas FDX2 Reveal Two Residues that, When Mutated, Partially Confer FDX2 the Redox Potential and Catalytic Properties of FDX1

    DOE PAGES

    Boehm, Marko; Alahuhta, Markus; Mulder, David W.; ...

    2015-11-03

    The green alga Chlamydomonas reinhardtii contains six plastidic [2Fe2S]-cluster ferredoxins (FDXs), with FDX1 as the predominant isoform under photoautotrophic growth. FDX2 is highly similar to FDX1 and has been shown to interact with specific enzymes (such as nitrite reductase), as well as to share interactors with FDX1, such as the hydrogenases (HYDA), ferredoxin:NAD(P) reductase I (FNR1), and pyruvate:ferredoxin oxidoreductase (PFR1), albeit performing at low catalytic rates. Here we report the FDX2 crystal structure solved at 1.18 Å resolution. Based on differences between the Chlorella fusca FDX1 and C. reinhardtii FDX2 structures, we generated and purified point-mutated versions of the FDX2more » protein and assayed them in vitro for their ability to catalyze hydrogen and NADPH photo-production. The data show that structural differences at two amino acid positions contribute to functional differences between FDX1 and FDX2, suggesting that FDX2 might have evolved from FDX1 toward a different physiological role in the cell. Moreover, we demonstrate that the mutations affect both the midpoint potentials of the FDX and kinetics of the FNR reaction, possibly due to altered binding between FDX and FNR. An effect on H2 photo-production rates was also observed, although the kinetics of the reaction were not further characterized.« less

  13. Redox biocatalysis and metabolism: molecular mechanisms and metabolic network analysis.

    PubMed

    Blank, Lars M; Ebert, Birgitta E; Buehler, Katja; Bühler, Bruno

    2010-08-01

    Whole-cell biocatalysis utilizes native or recombinant enzymes produced by cellular metabolism to perform synthetically interesting reactions. Besides hydrolases, oxidoreductases represent the most applied enzyme class in industry. Oxidoreductases are attributed a high future potential, especially for applications in the chemical and pharmaceutical industries, as they enable highly interesting chemistry (e.g., the selective oxyfunctionalization of unactivated C-H bonds). Redox reactions are characterized by electron transfer steps that often depend on redox cofactors as additional substrates. Their regeneration typically is accomplished via the metabolism of whole-cell catalysts. Traditionally, studies towards productive redox biocatalysis focused on the biocatalytic enzyme, its activity, selectivity, and specificity, and several successful examples of such processes are running commercially. However, redox cofactor regeneration by host metabolism was hardly considered for the optimization of biocatalytic rate, yield, and/or titer. This article reviews molecular mechanisms of oxidoreductases with synthetic potential and the host redox metabolism that fuels biocatalytic reactions with redox equivalents. The tools discussed in this review for investigating redox metabolism provide the basis for studies aiming at a deeper understanding of the interplay between synthetically active enzymes and metabolic networks. The ultimate goal of rational whole-cell biocatalyst engineering and use for fine chemical production is discussed.

  14. Redox Transformations of Mercury in Wetlands

    NASA Astrophysics Data System (ADS)

    Amyot, M.

    2007-12-01

    Wetlands are valued for their high biodiversity and for their ecosystem services. However, we still have a poor understanding of their role in the redox transformation of contaminants such as mercury. We first propose a brief overview of past studies conducted on wetlands from different latitudes. In most instances, photochemical processes are determinant in the upper portion of the water column. At the sediment/water interface, evidence is currently supporting a significant contribution of bacterial communities, as promoters of Hg(II) reduction, particularly in the presence of anoxia. A multi-year study was recently conducted on Hg redox cycling in a fluvial wetland of the St. Lawrence River, where wetland restoration could have unintended consequences. In addition to photochemistry and bacterial reduction, Hg redox cycling was affected by epiphytes living on macrophytes, through adsorption/absorption processes. Redox studies such as this one have been historically seen as having implication for water/air flux studies, since Hg(0) is volatile. We here also discuss the potential bioavailability of Hg(0) towards bacteria. An emerging axis of our wetland research effort deals with beaver dams, which are in expansion and shown to produce high levels of methylHg

  15. MITOCHONDRIAL REDOX IMAGING FOR CANCER DIAGNOSTIC AND THERAPEUTIC STUDIES

    PubMed Central

    LI, LIN Z.; XU, HE N.; RANJI, MAHSA; NIOKA, SHOKO; CHANCE, BRITTON

    2015-01-01

    Mitochondrial redox states provide important information about energy-linked biological processes and signaling events in tissues for various disease phenotypes including cancer. The redox scanning method developed at the Chance laboratory about 30 years ago has allowed 3D high-resolution (~ 50 × 50 × 10 μm3) imaging of mitochondrial redox state in tissue on the basis of the fluorescence of NADH (reduced nicotinamide adenine dinucleotide) and Fp (oxidized flavoproteins including flavin adenine dinucleotide, i.e., FAD). In this review, we illustrate its basic principles, recent technical developments, and biomedical applications to cancer diagnostic and therapeutic studies in small animal models. Recently developed calibration procedures for the redox imaging using reference standards allow quantification of nominal NADH and Fp concentrations, and the concentration-based redox ratios, e.g., Fp/(Fp+NADH) and NADH/(Fp+NADH) in tissues. This calibration facilitates the comparison of redox imaging results acquired for different metabolic states at different times and/or with different instrumental settings. A redox imager using a CCD detector has been developed to acquire 3D images faster and with a higher in-plane resolution down to 10 μm. Ex vivo imaging and in vivo imaging of tissue mitochondrial redox status have been demonstrated with the CCD imager. Applications of tissue redox imaging in small animal cancer models include metabolic imaging of glioma and myc-induced mouse mammary tumors, predicting the metastatic potentials of human melanoma and breast cancer mouse xenografts, differentiating precancerous and normal tissues, and monitoring the tumor treatment response to photodynamic therapy. Possible future directions for the development of redox imaging are also discussed. PMID:26015810

  16. Essential Role of Tissue-Specific Proline Synthesis and Catabolism in Growth and Redox Balance at Low Water Potential1[W][OA

    PubMed Central

    Sharma, Sandeep; Villamor, Joji Grace; Verslues, Paul E.

    2011-01-01

    To better define the still unclear role of proline (Pro) metabolism in drought resistance, we analyzed Arabidopsis (Arabidopsis thaliana) Δ1-pyrroline-5-carboxylate synthetase1 (p5cs1) mutants deficient in stress-induced Pro synthesis as well as proline dehydrogenase (pdh1) mutants blocked in Pro catabolism and found that both Pro synthesis and catabolism were required for optimal growth at low water potential (ψw). The abscisic acid (ABA)-deficient mutant aba2-1 had similar reduction in root elongation as p5cs1 and p5cs1/aba2-1 double mutants. However, the reduced growth of aba2-1 but not p5cs1/aba2-1 could be complemented by exogenous ABA, indicating that Pro metabolism was required for ABA-mediated growth protection at low ψw. PDH1 maintained high expression in the root apex and shoot meristem at low ψw rather than being repressed, as in the bulk of the shoot tissue. This, plus a reduced oxygen consumption and buildup of Pro in the root apex of pdh1-2, indicated that active Pro catabolism was needed to sustain growth at low ψw. Conversely, P5CS1 expression was most highly induced in shoot tissue. Both p5cs1-4 and pdh1-2 had a more reduced NADP/NADPH ratio than the wild type at low ψw. These results indicate a new model of Pro metabolism at low ψw whereby Pro synthesis in the photosynthetic tissue regenerates NADP while Pro catabolism in meristematic and expanding cells is needed to sustain growth. Tissue-specific differences in Pro metabolism and function in maintaining a favorable NADP/NADPH ratio are relevant to understanding metabolic adaptations to drought and efforts to enhance drought resistance. PMID:21791601

  17. Assessing the potential information content of multicomponent visual signals: a machine learning approach

    PubMed Central

    Allen, William L.; Higham, James P.

    2015-01-01

    Careful investigation of the form of animal signals can offer novel insights into their function. Here, we deconstruct the face patterns of a tribe of primates, the guenons (Cercopithecini), and examine the information that is potentially available in the perceptual dimensions of their multicomponent displays. Using standardized colour-calibrated images of guenon faces, we measure variation in appearance both within and between species. Overall face pattern was quantified using the computer vision ‘eigenface’ technique, and eyebrow and nose-spot focal traits were described using computational image segmentation and shape analysis. Discriminant function analyses established whether these perceptual dimensions could be used to reliably classify species identity, individual identity, age and sex, and, if so, identify the dimensions that carry this information. Across the 12 species studied, we found that both overall face pattern and focal trait differences could be used to categorize species and individuals reliably, whereas correct classification of age category and sex was not possible. This pattern makes sense, as guenons often form mixed-species groups in which familiar conspecifics develop complex differentiated social relationships but where the presence of heterospecifics creates hybridization risk. Our approach should be broadly applicable to the investigation of visual signal function across the animal kingdom. PMID:25652832

  18. Applied potential tomography shows differential changes in fluid content of leg tissue layers in microgravity

    NASA Astrophysics Data System (ADS)

    Baisch, F. J.

    1994-08-01

    Absence of hydrostatic forces in the human cardiocirculatory system normally leads to an overall body fluid deficit. It was hypothesized that this is mainly due to a loss of interstitial fluid. An experiment was performed on board the Russian MIR station. Cuffs were positioned around both thighs and inflated up to suprasystolic values. This maneuver took place just before and after immediately a lower body negative pressure session (LBNP). The redistribution of fluids underneath the cuffs was assessed by means of cross-sectional impedance tomography (Applied Potential Tomography, APT). A μ-g induced loss of interstitial fluid was measured in all layers of the observed cross-section. The APT-readings changed significantly (SD~+/-.9) from 3.0 at 1g to 1.7 at 0g for the outer layer and from 2.7 at 1g to 2.0 at 0g for the middle layer (expressed in arbitrary units). The LBNP maneuver was able to fill the interstitial space but only at levels higher than - 15 mmHg LBNP. This suggests that the superficial tissues in the legs are as much affected as the deeper ones by changing g-conditions and LBNP can be used to counteract interstitial fluid loss in this area.

  19. Clostridium thermocellum DSM 1313 transcriptional responses to redox perturbation

    DOE PAGES

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

    2015-12-12

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

  20. Study to establish cost projections for production of Redox chemicals

    NASA Technical Reports Server (NTRS)

    Walther, J. F.; Greco, C. C.; Rusinko, R. N.; Wadsworth, A. L., III

    1982-01-01

    A cost study of four proposed manufacturing processes for redox chemicals for the NASA REDOX Energy Storage System yielded favorable selling prices in the range $0.99 to $1.91/kg of chromic chloride, anhydrous basis, including ferrous chloride. The prices corresponded to specific energy storage costs from under $9 to $17/kWh. A refined and expanded cost analysis of the most favored process yielded a price estimate corresponding to a storage cost of $11/kWh. The findings supported the potential economic viability of the NASA REDOX system.

  1. Intensity of blue LED light: a potential stimulus for biomass and lipid content in fresh water microalgae Chlorella vulgaris.

    PubMed

    Atta, Madiha; Idris, Ani; Bukhari, Ataullah; Wahidin, Suzana

    2013-11-01

    Light quality and the intensity are key factors which render microalgae as a potential source of biodiesel. In this study the effects of various intensities of blue light and its photoperiods on the growth and lipid content of Chlorella vulgaris were investigated by using LED (Light Emitting Diode) in batch culture. C. vulgaris was grown for 13 days at three different light intensities (100, 200 and 300 μmol m(-2)s(-1)). Effect of three different light and dark regimes (12:12, 16:08 and 24:00 h Light:Dark) were investigated for each light intensity at 25°C culture temperature. Maximum lipid content (23.5%) was obtained due to high efficiency and deep penetration of 200 μmol m(-2)s(-1) of blue light (12:12 L:D) with improved specific growth (1.26 d(-1)) within reduced cultivation time of 8 days. White light could produce 20.9% lipid content in 10 days at 16:08 h L:D.

  2. High Content Screening Analysis to Evaluate the Toxicological Effects of Harmful and Potentially Harmful Constituents (HPHC)

    PubMed Central

    Marescotti, Diego; Gonzalez Suarez, Ignacio; Acali, Stefano; Johne, Stephanie; Laurent, Alexandra; Frentzel, Stefan; Hoeng, Julia; Peitsch, Manuel C.

    2016-01-01

    Cigarette smoke (CS) is a major risk factor for cardiovascular and lung diseases. Because CS is a complex aerosol containing more than 7,000 chemicals1 it is challenging to assess the contributions of individual constituents to its overall toxicity. Toxicological profiles of individual constituents as well as mixtures can be however established in vitro, by applying high through-put screening tools, which enable the profiling of Harmful and Potentially Harmful Constituents (HPHCs) of tobacco smoke, as defined by the U.S. Food and Drug Administration (FDA).2 For an initial assessment, an impedance-based instrument was used for a real-time, label-free assessment of the compound's toxicity. The instrument readout relies on cell adhesion, viability and morphology that all together provide an overview of the cell status. A dimensionless parameter, named cell index, is used for quantification. A set of different staining protocols was developed for a fluorescence imaging-based investigation and a HCS platform was used to gain more in-depth information on the kind of cytotoxicity elicited by each HPHC. Of the 15 constituents tested, only five were selected for HCS-based analysis as they registered a computable LD50 (< 20 mM). These included 1-aminonaphtalene, Arsenic (V), Chromium (VI), Crotonaldehyde and Phenol. Based on their effect in the HCS, 1-aminonaphtalene and Phenol could be identified to induce mitochondrial dysfunction, and, together with Chromium (VI) as genotoxic based on the increased histone H2AX phosphorylation. Crotonaldehyde was identified as an oxidative stress inducer and Arsenic as a stress kinase pathway activator. This study demonstrates that a combination of impedance-based and HCS technologies provides a robust tool for in vitro assessment of CS constituents. PMID:27228213

  3. Inherent organic compounds in biochar--Their content, composition and potential toxic effects.

    PubMed

    Buss, Wolfram; Mašek, Ondřej; Graham, Margaret; Wüst, Dominik

    2015-06-01

    Pyrolysis liquids consist of thermal degradation products of biomass in various stages of its decomposition. Therefore, if biochar gets affected by re-condensed pyrolysis liquids it is likely to contain a huge variety of organic compounds. In this study the chemical composition of such compounds associated with two contaminated, high-volatile organic compound (VOC) biochars were investigated and compared with those for a low-VOC biochar. The water-soluble organic compounds with the highest concentrations in the two high-VOC biochars were acetic, formic, butyric and propionic acids; methanol, phenol, o-, m- and p-cresol, and 2,4-dimethylphenol, all with concentrations over 100 μg g(-1). The concentrations of 16 US EPA PAHs determined by 36 h toluene extractions were 6.09 μg g(-1) for the low-VOC biochar. For high-VOC biochar the total concentrations were 53.42 μg g(-1) and 27.89 μg g(-1), while concentrations of water-soluble PAHs ranged from 1.5 to 2 μg g(-1). Despite the concentrations of PAHs exceeding biochar guideline values, it was concluded that, for these particular biochars, the biggest concern for application to soil would be the co-occurrence of VOCs such as low molecular weight (LMW) organic acids and phenols, as these can be highly mobile and have a high potential to cause phytotoxic effects. Therefore, based on results of this study we strongly suggest for VOCs to be included among criteria for assessment of biochar quality.

  4. Application of a high-content multiparameter cytotoxicity assay to prioritize compounds based on toxicity potential in humans.

    PubMed

    Abraham, Vivek C; Towne, Danli L; Waring, Jeffrey F; Warrior, Usha; Burns, David J

    2008-07-01

    Prioritization of compounds based on human hepatotoxicity potential is currently a key unmet need in drug discovery, as it can become a major problem for several lead compounds in later stages of the drug discovery pipeline. The authors report the validation and implementation of a high-content multiparametric cytotoxicity assay based on simultaneous measurement of 8 key cell health indicators associated with nuclear morphology, plasma membrane integrity, mitochondrial function, and cell proliferation. Compounds are prioritized by (a) computing an in vitro safety margin using the minimum cytotoxic concentration (IC(20)) across all 8 indicators and cell-based efficacy data and (b) using the minimal cytotoxic concentration alone to take into account concentration of drug in tissues. Feasibility data using selected compounds, including quinolone antibiotics, thiazolidinediones, and statins, suggest the viability of this approach. To increase overall throughput of compound prioritization, the authors have identified the higher throughput, plate reader-based CyQUANT assay that is similar to the high-content screening (HCS) assay in sensitivity of measuring inhibition of cell proliferation. It is expected that the phenotypic output from the multiparametric HCS assay in combination with other highly sensitive approaches, such as microarray-based expression analysis of toxic signatures, will contribute to a better understanding and predictivity of human hepatotoxicity potential.

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

    PubMed

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

    2010-12-01

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

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

    NASA Astrophysics Data System (ADS)

    Rose, Andrew

    2016-11-01

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

  7. Content and evolution of potential furfural compounds in commercial milk-based infant formula powder after opening the packet.

    PubMed

    Chávez-Servín, Jorge L; de la Torre Carbot, Karina; García-Gasca, Teresa; Castellote, Ana I; López-Sabater, M Carmen

    2015-01-01

    Potential furfural compounds were examined by RP-HPLC-DAD in 20 commercial milk-based powdered infant formula (IF) brands from local markets from Paris, France; DF, Mexico; Copenhagen, Denmark; England, UK; and Barcelona, Spain. We traced the evolution of these compounds after the packets had been opened at 0, 30 and 70 days of storage at room temperature (≈25 °C; minimum 23 °C and maximum 25.5 °C). All formula brands were analysed during the first 3-5 months of their shelf life. The mean values of all IFs for potential 5-hydroxymethyl-2-furaldehyde (HMF)+2-furaldehyde (F) were 1115.2 μg/100 g (just opened), 1157.6 μg/100 g (30 days) and 1344.5 μg/100 g of product (70 days). In general, slight increases of potential furfural contents were observed in most of the studied IFs, which suggests that the Maillard reaction increases after opening the packets. The main furfural compound found was HMF, as expected. The range of potential HMF consumed for an infant about 6 months old feeding only on formula was estimated between 0.63 mg and 3.25 mg per day.

  8. The Redox Stress Hypothesis of Aging

    PubMed Central

    Sohal, Rajindar S.; Orr, William C.

    2011-01-01

    The main objective of this review is to examine the role of the endogenous reactive oxygen/nitrogen species (ROS) in the aging process. Until relatively recently, ROS were considered to be potentially toxic by-products of aerobic metabolism, which, if not eliminated, may inflict structural damage on various macromolecules. Accrual of such damage over time was postulated to be responsible for the physiological deterioration in the post-reproductive phase of life and eventually the death of the organism. This “structural damage-based oxidative stress” hypothesis has received support from the age-associated increases in the rates of ROS production and the steady-state amounts of oxidized macromolecules; however, there are increasing indications that structural damage alone is insufficient to satisfactorily explain the age-associated functional losses. The level of oxidative damage, accrued during aging, often does not match the magnitude of functional losses. Although experimental augmentations of antioxidant defenses tend to enhance resistance to induced oxidative stress, such manipulations are generally ineffective in the extension of life span of long-lived strains of animals. More recently, in a major conceptual shift, ROS have been found to be physiologically vital for signal transduction, gene regulation and redox regulation, among others, implying that their complete elimination would be harmful. An alternative notion, advocated here, termed “redox stress hypothesis”, proposes that aging-associated functional losses are primarily caused by a progressive pro-oxidizing shift in the redox state of the cells, which leads to the over-oxidation of redox-sensitive protein thiols and the consequent disruption of the redox-regulated signaling mechanisms. PMID:22080087

  9. Redox flow batteries: a review

    SciTech Connect

    Weber, Adam Z.; Mench, Matthew M; Meyers, Jeremy; Ross, Philip N.; Gostick, Jeffrey T.; Liu, Qinghua

    2011-01-01

    Redox flow batteries (RFBs) are enjoying a renaissance due to their ability to store large amounts of electrical energy relatively cheaply and efficiently. In this review, we examine the components of RFBs with a focus on understanding the underlying physical processes. The various transport and kinetic phenomena are discussed along with the most common redox couples.

  10. Unusual thiol-based redox metabolism of parasitic flukes.

    PubMed

    Tripathi, Timir; Suttiprapa, Sutas; Sripa, Banchob

    2016-05-27

    Parasitic flukes are exposed to free radicals and, to a greater extent, reactive oxygen species (ROS) during their life cycle. Despite being relentlessly exposed to ROS released by activated immune cells, these parasites can survive for many years in the host. Cellular thiol-based redox metabolism plays a crucial role in parasite survival within their hosts. Evidence shows that oxidative stress and redox homeostasis maintenance are important clinical and pathobiochemical as well as effective therapeutic principles in various diseases. The characterization of redox and antioxidant enzymes is likely to yield good target candidates for novel drugs and vaccines. The absence of active catalase in fluke parasites offers great potential for the development of chemotherapeutic agents that act by perturbing the redox equilibrium of the cell. One of the redox-sensitive enzymes, thioredoxin glutathione reductase (TGR), has been accepted as a drug target against blood fluke infections, and related clinical trials are in progress. TGR is the sole enzyme responsible for Trx and GSH reduction in parasitic flukes. The availability of helminth genomes has accelerated the research on redox metabolism of flukes; however, significant achievements have yet to be attained. The present review summarizes current knowledge on the redox and antioxidant system of the parasitic flukes.

  11. Bicarbonate Induced Redox Proteome Changes in Arabidopsis Suspension Cells

    PubMed Central

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

    2017-01-01

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

  12. Problems in Teaching the Topic of Redox Reactions: Actions and Conceptions of Chemistry Teachers.

    ERIC Educational Resources Information Center

    De Jong, Onno; And Others

    1995-01-01

    Presents a case study of problems that can occur when teaching the topic of redox reactions to grade-11 students. Concludes that the teachers' scientific expertise is an important source of difficulties when teaching redox reactions. Discusses implications for improvement of current chemistry classroom practice and content-related teacher…

  13. Redox properties of structural Fe in clay minerals. 1. Electrochemical quantification of electron-donating and -accepting capacities of smectites.

    PubMed

    Gorski, Christopher A; Aeschbacher, Michael; Soltermann, Daniela; Voegelin, Andreas; Baeyens, Bart; Marques Fernandes, Maria; Hofstetter, Thomas B; Sander, Michael

    2012-09-04

    Clay minerals often contain redox-active structural iron that participates in electron transfer reactions with environmental pollutants, bacteria, and biological nutrients. Measuring the redox properties of structural Fe in clay minerals using electrochemical approaches, however, has proven to be difficult due to a lack of reactivity between clay minerals and electrodes. Here, we overcome this limitation by using one-electron-transfer mediating compounds to facilitate electron transfer between structural Fe in clay minerals and a vitreous carbon working electrode in an electrochemical cell. Using this approach, the electron-accepting and -donating capacities (Q(EAC) and Q(EDC)) were quantified at applied potentials (E(H)) of -0.60 V and +0.61 V (vs SHE), respectively, for four natural Fe-bearing smectites (i.e., SWa-1, SWy-2, NAu-1, and NAu-2) having different total Fe contents (Fe(total) = 2.3 to 21.2 wt % Fe) and varied initial Fe(2+)/Fe(total) states. For every SWa-1 and SWy-2 sample, all the structural Fe was redox-active over the tested E(H) range, demonstrating reliable quantification of Fe content and redox state. Yet for NAu-1 and NAu-2, a significant fraction of the structural Fe was redox-inactive, which was attributed to Fe-rich smectites requiring more extreme E(H)-values to achieve complete Fe reduction and/or oxidation. The Q(EAC) and Q(EDC) values provided here can be used as benchmarks in future studies examining the extent of reduction and oxidation of Fe-bearing smectites.

  14. Redox control of GTPases: from molecular mechanisms to functional significance in health and disease.

    PubMed

    Heo, Jongyun

    2011-02-15

    Small GTPases, including the proto-oncoprotein Ras and Rho GTPases, are involved in various cellular signaling events. Some of these small GTPases are redox sensitive, including Ras, Rho, Ran, Dexras1, and Rhes GTPases. Thus, the redox-mediated regulation of these GTPases often determines the course of their cellular signaling cascades. This article takes into consideration the application of Marcus theory to potential redox-based molecular mechanisms in the regulation of these redox-sensitive GTPases and the relevance of such mechanisms to a specific redox-sensitive motif. The discussion also takes into account various diseases, including cancers, heart, and neuronal disorders, that are often linked with the dysregulation of the redox signaling cascades associated with these redox-sensitive GTPases.

  15. Different redox states of metallothionein/thionein in biological tissue

    PubMed Central

    Krężel, Artur; Maret, Wolfgang

    2006-01-01

    Mammalian metallothioneins are redox-active metalloproteins. In the case of zinc metallothioneins, the redox activity resides in the cysteine sulfur ligands of zinc. Oxidation releases zinc, whereas reduction re-generates zinc-binding capacity. Attempts to demonstrate the presence of the apoprotein (thionein) and the oxidized protein (thionin) in tissues posed tremendous analytical challenges. One emerging strategy is differential chemical modification of cysteine residues in the protein. Chemical modification distinguishes three states of the cysteine ligands (reduced, oxidized and metal-bound) based on (i) quenched reactivity of the thiolates when bound to metal ions and restoration of thiol reactivity in the presence of metal-ion-chelating agents, and (ii) modification of free thiols with alkylating agents and subsequent reduction of disulfides to yield reactive thiols. Under normal physiological conditions, metallothionein exists in three states in rat liver and in cell lines. Ras-mediated oncogenic transformation of normal HOSE (human ovarian surface epithelial) cells induces oxidative stress and increases the amount of thionin and the availability of cellular zinc. These experiments support the notion that metallothionein is a dynamic protein in terms of its redox state and metal content and functions at a juncture of redox and zinc metabolism. Thus redox control of zinc availability from this protein establishes multiple methods of zinc-dependent cellular regulation, while the presence of both oxidized and reduced states of the apoprotein suggest that they serve as a redox couple, the generation of which is controlled by metal ion release from metallothionein. PMID:17134375

  16. In vitro evaluation of the antioxidant potential, phenolic and flavonoid contents of the stem bark ethanol extract of Anogeissus leiocarpus

    PubMed Central

    Olugbami, JO; Gbadegesin, MA

    2015-01-01

    Plant-derived antioxidants with free radical scavenging activities can be relevant as chemopreventive agents against the numerous diseases associated with free radicals and reactive oxygen species. Some phytoconstituents possess antioxidant activities in biological systems. On this basis, we evaluated the antioxidant potential, and determined the total phenolic and flavonoid contents of the ethanol extract of the stem bark of Anogeissus leiocarpus [EESAL]. Antioxidant assays carried out include: 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, phosphomolybdate, β-carotene bleaching, ferric reducing, and hydroxyl radical scavenging activities. Results of DPPH assay showed no significant difference (p < 0.001) between EESAL and butylated hydroxyanisole [BHA], while EESAL exhibited a significantly (p < 0.001) higher activity than BHT [butylated hydroxytoluene]. Phosphomolybdate method recorded a total antioxidant capacity of 190.00 ± 70.53 µg butylated hydroxytoluene equivalents [BHTE]/mg dry extract, while β-carotene bleaching assay gave percent antioxidant activities of both EESAL and BHT as 81.46±1.62 and 80.90±1.39 respectively. Ferric reducing abilities of both EESAL and ascorbic acid increased in a concentration-dependent manner with EESAL displaying a significantly (p < 0.001) higher reductive activity than vitamin C. EESAL displayed a significantly higher hydroxyl radical scavenging activity as compared with BHT at the lowest concentration with no significant difference at the highest concentration. Total phenolic and flavonoid contents of EESAL were obtained as 608.10 ± 2.12 µg GAE/mg and 78.96 ± 3.37 µg QE/mg respectively. Taken together, the free radical scavenging and antioxidant activity of EESAL is likely due to its high phenolic content with complementary effects of the flavonoid components. PMID:26681826

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  18. Potential health concerns of trace elements and mineral content in commonly consumed greenhouse vegetables in Isfahan, Iran

    PubMed Central

    Abdi, Mohammad Reza; Rezaee-Ebrahim-Saraee, Khadijeh; Fard, Mehdi Rezvani; Baradaran-Ghahfarokhi, Milad

    2015-01-01

    Background: This study aimed to investigate the potential health concerns of trace elements and mineral content of commonly consumed greenhouse vegetables in Isfahan, Iran. Materials and Methods: Six kinds of greenhouse vegetables namely; Raphanus sativus (Radish), Cucumis sativus (Cucumber), Solanum lycopersicum (Tomato), green Capsicum annuum (Green bell pepper), yellow C. annuum (Yellow bell pepper), and red C. annuum (Red bell pepper) were collected from Isfahan greenhouses, between December 2012 and March 2013. The vegetables were analyzed in order to determine the concentrations of trace elements and trace minerals using instrumental neutron activation analysis (INAA). Results: The results of INAA showed that the concentrations of aluminum, bromine, cobalt, rubidium and strontium of these vegetables were varied from 7.2 to 28.4 mg/kg, 0.6–11.7 mg/kg, 0.1–0.5 mg/kg, 4.2–8.4 mg/kg, and 12.0–141.0 mg/kg, respectively. The trace mineral concentrations of As, Cr, Cs, Sc, Th, and U in all of the samples were less than the defined tolerable upper intake level. Conclusion: The results of this study revealed that considering the measured trace elements and mineral content levels, Isfahan greenhouse vegetables do not impose any serious health harmful effects for individuals in the studied area due to their meal consumptions. PMID:26605243

  19. Effect of ionising radiation on polyphenolic content and antioxidant potential of parathion-treated sage (Salvia officinalis) leaves.

    PubMed

    Ben Salem, Issam; Fekih, Sana; Sghaier, Haitham; Bousselmi, Mehrez; Saidi, Mouldi; Landoulsi, Ahmed; Fattouch, Sami

    2013-11-15

    The γ-irradiation effects on polyphenolic content and antioxidant capacity of parathion-pretreated leaves of Salvia officinalis plant were investigated. The analysis of phenolic extracts of sage without parathion showed that irradiation decreased polyphenolic content significantly (p<0.05) by 30% and 45% at 2 and 4kGy, respectively, compared to non-irradiated samples. The same trend was observed for the Trolox equivalent antioxidant capacity (TEAC), as assessed by the anionic DPPH and cationic ABTS radical-scavenging assays. The antioxidant potential decreased significantly (p<0.01) at 2 and 4kGy, by 11-20% and 40-44%, respectively. The results obtained with a pure chlorogenic acid solution confirmed the degradation of phenols; however, its TEAC was significantly (p<0.01) increased following irradiation. Degradation products of parathion formed by irradiation seem to protect against a decline of antioxidant capacity and reduce polyphenolic loss. Ionising radiation was found to be useful in breaking down pesticide residues without inducing significant losses in polyphenols.

  20. Redox biology of the intestine

    PubMed Central

    Circu, Magdalena L.; Aw, Tak Yee

    2011-01-01

    The intestinal tract, known for its capability for self-renew, represents the first barrier of defense between the organism and its luminal environment. The thiol/disulfide redox systems comprising the glutathione/glutathione disulfide (GSH/GSSG), cysteine/cystine (Cys/CySS) and reduced and oxidized thioredoxin (Trx/TrxSS) redox couples play important roles in preserving tissue redox homeostasis, metabolic functions, and cellular integrity. Control of the thiol-disulfide status at the luminal surface is essential for maintaining mucus fluidity and absorption of nutrients, and protection against chemical-induced oxidant injury. Within intestinal cells, these redox couples preserve an environment that supports physiological processes and orchestrates networks of enzymatic reactions against oxidative stress. In this review, we focus on the intestinal redox and antioxidant systems, their subcellular compartmentation, redox signaling and epithelial turnover, and contribution of luminal microbiota, key aspects that are relevant to understanding redox-dependent processes in gut biology with implications for degenerative digestive disorders, such as inflammation and cancer. PMID:21831010

  1. Redox shuttles for overcharge protection of lithium batteries

    DOEpatents

    Amine, Khalil; Chen, Zonghai; Wang, Qingzheng

    2010-12-14

    The present invention is generally related to electrolytes containing novel redox shuttles for overcharge protection of lithium-ion batteries. The redox shuttles are capable of thousands hours of overcharge tolerance and have a redox potential at about 3-5.5 V vs. Li and particularly about 4.4-4.8 V vs. Li. Accordingly, in one aspect the invention provides electrolytes comprising an alkali metal salt; a polar aprotic solvent; and a redox shuttle additive that is an aromatic compound having at least one aromatic ring with four or more electronegative substituents, two or more oxygen atoms bonded to the aromatic ring, and no hydrogen atoms bonded to the aromatic ring; and wherein the electrolyte solution is substantially non-aqueous. Further there are provided electrochemical devices employing the electrolyte and methods of making the electrolyte.

  2. Dynamic Regulation of the GABAA Receptor Function by Redox Mechanisms.

    PubMed

    Calvo, Daniel J; Beltrán González, Andrea N

    2016-09-01

    Oxidizing and reducing agents, which are currently involved in cell metabolism and signaling pathways, can regulate fast inhibitory neurotransmission mediated by GABA receptors in the nervous system. A number of in vitro studies have shown that diverse redox compounds, including redox metabolites and reactive oxygen and nitrogen species, modulate phasic and tonic responses mediated by neuronal GABAA receptors through both presynaptic and postsynaptic mechanisms. We review experimental data showing that many redox agents, which are normally present in neurons and glia or are endogenously generated in these cells under physiologic states or during oxidative stress (e.g., hydrogen peroxide, superoxide and hydroxyl radicals, nitric oxide, ascorbic acid, and glutathione), induce potentiating or inhibiting actions on different native and recombinant GABAA receptor subtypes. Based on these results, it is thought that redox signaling might represent a homeostatic mechanism that regulates the function of synaptic and extrasynaptic GABAA receptors in physiologic and pathologic conditions.

  3. Donor/Acceptor Mixed Self-Assembled Monolayers for Realising a Multi-Redox-State Surface.

    PubMed

    Casado-Montenegro, Javier; Marchante, Elena; Crivillers, Núria; Rovira, Concepció; Mas-Torrent, Marta

    2016-06-17

    Mixed molecular self-assembled monolayers (SAMs) on gold, based on two types of electroactive molecules, that is, electron-donor (ferrocene) and electron-acceptor (anthraquinone) molecules, are prepared as an approach to realise surfaces exhibiting multiple accessible redox states. The SAMs are investigated in different electrolyte media. The nature of these media has a strong impact on the types of redox processes that take place and on the redox potentials. Under optimised conditions, surfaces with three redox states are achieved. Such states are accessible in a relatively narrow potential window in which the SAMs on gold are stable. This communication elucidates the key challenges in fabricating bicomponent SAMs as electrochemical switches.

  4. Anti-inflammatory potential of flavonoid contents from dried fruit of Crataegus pinnatifida in vitro and in vivo.

    PubMed

    Kao, Erl-Shyh; Wang, Chau-Jong; Lin, Wea-Lung; Yin, Yu-Fang; Wang, Chi-Pin; Tseng, Tsui-Hwa

    2005-01-26

    The dried fruits of Crataegus pinnatifida, a local soft drink material and medical herb, demonstrated antioxidant effect in a previous study. The present study investigates the anti-inflammatory potential of flavonoid contents from dried fruit of C. pinnatifida (CF-Fs). The preliminary investigation showed that CF-Fs (0.25-0.75 mg/mL) decreased the release of PGE2 and nitric oxide as induced by lipopolysaccharide (LPS, an endotoxin) in macrophage RAW 264.7 cells. The in vivo assay showed that pretreatment of rats with CF-Fs (50-200 mg/kg dosed by gavage) for 5 days significantly decreased the serum levels of the hepatic enzyme markers alanine aminotransferase and aspartate aminotransferase induced by the 6-h treatment with LPS (i.p.; 5 mg/kg). Histopathological evaluation of the rat livers revealed that CF-Fs reduced the incidence of liver lesions such as neutrophil infiltration and necrosis induced by LPS. Furthermore, it was found that pretreatment with CF-Fs decreased the hepatic expression of iNOS and COX-2 induced by LPS in rats. These results demonstrate that CF-Fs present anti-inflammatory potential in vitro and in vivo and that they may play a role in hepatoprotection.

  5. 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.

  6. Redox reactions of apo mammalian ferritin.

    PubMed

    Watt, R K; Frankel, R B; Watt, G D

    1992-10-13

    Apo horse spleen ferritin undergoes a 6.3 +/- 0.5 electron redox reaction at -310 mV at pH 6.0-8.5 and 25 degrees C to form reduced apoferritin (apoMFred). Reconstituted ferritin containing up to 50 ferric ions undergoes reduction at the same potential, taking up one electron per ferric ion and six additional electrons by the protein. We propose that apo mammalian ferritin (apoMF) contains six redox centers that can be fully oxidized forming oxidized apoferritin (apoMFox) or fully reduced forming apoMFred. ApoMFred can be prepared conveniently by dithionite or methyl viologen reduction. ApoMFred is slowly oxidized by molecular oxygen but more rapidly by Fe(CN)6(3-) to apoMFox. Fe(III)-cytochrome c readily oxidizes apoMFred to apoMFox with a stoichiometry of 6 Fe(III)-cytochrome c per apoMFred, demonstrating a rapid interprotein electron-transfer reaction. Both redox states of apoMF react with added Fe3+ and Fe2+. Addition of eight Fe2+ to apoMFox under anaerobic conditions produced apoMFred and Fe3+, as evidenced by the presence of a strong g = 4.3 EPR signal. Subsequent addition of bipyridyl produced at least six Fe(bipyd)3(2+) per MF, establishing the reversibility of this internal electron-transfer process between the redox centers of apoMF and bound iron. Incubation of apoMFred with the Fe(3+)-ATP complex under anaerobic conditions resulted in the formation and binding of two Fe2+ and four Fe3+ by the protein. The various redox states formed by the binding of Fe2+ and Fe3+ to apoMFox and apoMFred are proposed and discussed. The yellow color of apoMF appears to be an integral characteristic of the apoMF and is possibly associated with its redox activity.

  7. 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...

  8. Phenolic contents, antioxidant and anticholinesterase potentials of crude extract, subsequent fractions and crude saponins from Polygonum hydropiper L

    PubMed Central

    2014-01-01

    Background We investigated Polygonum hydropiper L. (P. hydropiper) for phenolic contents, antioxidant, anticholinesterase activities, in an attempt to rationalize its use in neurological disorders. Methods Plant crude extract (Ph.Cr), its subsequent fractions: n-hexane (Ph.Hex), chloroform (Ph.Chf), ethyl acetate (Ph.EtAc), n-Butanol (Ph.Bt), aqueous (Ph.Aq) and saponins (Ph.Sp) were evaluated for 1,1-diphenyl,2-picrylhydrazyl (DPPH), 2,2-azinobis[3-ethylbenzthiazoline]-6-sulfonic acid (ABTS) free radical scavenging potential. Further, acetylcholinesterase (AChE) & butyrylcholinesterase (BChE) inhibitory activities were performed using Ellman's assay. Moreover, total phenolic contents of plant extracts were determined and expressed in mg of gallic acid equivalent per gram of dry sample (mg GAE/g dry weight). Results Among different fractions, Ph.Cr (90.82), Ph.Chf (178.16), Ph.EtAc (203.44) and Ph.Bt (153.61) exhibited high phenolic contents. All fractions showed concentration dependent DPPH scavenging activity, with Ph.EtAc 71.33% (IC50 15 μg/ml), Ph.Bt 71.40% (IC50 3 μg/ml) and Ph.Sp 71.40% (IC50 35 μg/ml) were most potent. The plant extracts exhibited high ABTS scavenging ability i.e. Ph.Bt (91.03%), Ph.EtAc (90.56%), Ph.Sp (90.84%), Ph.Aq (90.56%) with IC50 < 0.01 μg/ml. All fractions showed moderate to high AChE inhibitory activity as; Ph.Cr, 86.87% (IC50 330 μg/ml), Ph.Hex, 87.49% (IC50 35 μg/ml), Ph.Chf, 84.76% (IC50 55 μg/ml), Ph.Sp, 87.58% (IC50 108 μg/ml) and Ph.EtAc 79.95% (IC50 310 μg/ml) at 1 mg/ml). Furthermore the BChE inhibitory activity was most prominent in Ph.Hex 90.30% (IC50 40 μg/ml), Ph.Chf 85.94% (IC50 215 μg/ml), Ph.Aq 87.62% (IC50 3 μg/ml) and Ph.EtAc 81.01% (IC50 395 μg/ml) fractions. Conclusions In this study, for the first time, we determined phenolic contents, isolated crude saponins, investigated antioxidant and anticholinestrase potential of P. hydropiper extracts. The results indicate that P. hydropiper

  9. Bioturbating animals control the mobility of redox-sensitive trace elements in organic-rich mudstone

    SciTech Connect

    Harazim, Dario; McIlroy, Duncan; Edwards, Nicholas P.; Wogelius, Roy A.; Manning, Phillip L.; Poduska, Kristin M.; Layne, Graham D.; Sokaras, Dimosthenis; Alonso-Mori, Roberto; Bergmann, Uwe

    2015-10-07

    Bioturbating animals modify the original mineralogy, porosity, organic content, and fabric of mud, thus affecting the burial diagenetic pathways of potential hydrocarbon source, seal, and reservoir rocks. High-sensitivity, synchrotron rapid scanning X-ray fluorescence elemental mapping reveals that producers of phycosiphoniform burrows systematically partition redox-sensitive trace elements (i.e., Fe, V, Cr, Mn, Co, Ni, Cu, and As) in fine-grained siliciclastic rocks. Systematic differences in organic carbon content (total organic carbon >1.5 wt%) and quality (Δ13Corg~0.6‰) are measured between the burrow core and host sediment. The relative enrichment of redox-sensitive elements in the burrow core does not correlate with significant neo-formation of early diagenetic pyrite (via trace metal pyritization), but is best explained by physical concentration of clay- and silt-sized components. A measured loss (~–15%) of the large-ionic-radius elements Sr and Ba from both burrow halo and core is most likely associated with the release of Sr and Ba to pore waters during biological (in vivo) weathering of silt- to clay-sized lithic components and feldspar. In conclusion, this newly documented effect has significant potential to inform the interpretation of geochemical proxy and rock property data, particularly from shales, where elemental analyses are commonly employed to predict reservoir quality and support paleoenvironmental analysis.

  10. Bioturbating animals control the mobility of redox-sensitive trace elements in organic-rich mudstone

    DOE PAGES

    Harazim, Dario; McIlroy, Duncan; Edwards, Nicholas P.; ...

    2015-10-07

    Bioturbating animals modify the original mineralogy, porosity, organic content, and fabric of mud, thus affecting the burial diagenetic pathways of potential hydrocarbon source, seal, and reservoir rocks. High-sensitivity, synchrotron rapid scanning X-ray fluorescence elemental mapping reveals that producers of phycosiphoniform burrows systematically partition redox-sensitive trace elements (i.e., Fe, V, Cr, Mn, Co, Ni, Cu, and As) in fine-grained siliciclastic rocks. Systematic differences in organic carbon content (total organic carbon >1.5 wt%) and quality (Δ13Corg~0.6‰) are measured between the burrow core and host sediment. The relative enrichment of redox-sensitive elements in the burrow core does not correlate with significant neo-formation ofmore » early diagenetic pyrite (via trace metal pyritization), but is best explained by physical concentration of clay- and silt-sized components. A measured loss (~–15%) of the large-ionic-radius elements Sr and Ba from both burrow halo and core is most likely associated with the release of Sr and Ba to pore waters during biological (in vivo) weathering of silt- to clay-sized lithic components and feldspar. In conclusion, this newly documented effect has significant potential to inform the interpretation of geochemical proxy and rock property data, particularly from shales, where elemental analyses are commonly employed to predict reservoir quality and support paleoenvironmental analysis.« less

  11. Redox regulation of Ran GTPase

    SciTech Connect

    Heo, Jongyun

    2008-11-21

    Ran, a small Ras-like GTP-binding nuclear protein, plays a key role in modulation of various cellular signaling events including the cell cycle. This study shows that a cellular redox agent (nitrogen dioxide) facilitates Ran guanine nucleotide dissociation, and identifies a unique Ran redox architecture involved in that process. Sequence analysis suggests that Dexras1 and Rhes GTPases also possess the Ran redox architecture. As Ran releases an intact nucleotide, the redox regulation mechanism of Ran is likely to differ from the radical-based guanine nucleotide modification mechanism suggested for Ras and Rho GTPases. These results provide a mechanistic reason for the previously observed oxidative stress-induced perturbation of the Ran-mediated nuclear import, and suggest that oxidative stress could be a factor in the regulation of cell signal transduction pathways associated with Ran.

  12. Thiol-Based Redox Switches

    PubMed Central

    Groitl, Bastian; Jakob, Ursula

    2014-01-01

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

  13. Report: Factors affecting the content of potentially toxic elements in the biodegradable fraction of autoclaved household waste.

    PubMed

    Papadimitriou, Efstathios K; Barton, John R

    2009-10-01

    A total of 3.4 tonnes of household waste (HW) that had a controlled composition were autoclaved in the presence of saturated steam for 1 h at the nominal temperature levels of 130, 160 and 200 degrees C. The levels of Cd, Cr, Cu, Pb, Hg, Ni, and Zn were examined in samples of the fibrous, predominantly-biodegradable fraction (floc) derived from the autoclaved HW, aqueous extracts from floc, and the condensate from steam that was released from the reactor. This data was used to study the impact of the overall levels of potential toxic elements (PTEs) in HW feed and autoclaving process parameters on the levels of PTEs in floc. No consistent correlation was found to exist between the levels of PTEs in HW feed and those in the produced floc. This was primarily attributed in the inherent variability of PTEs in waste materials. Autoclaving temperature, pressure and mixing were all found to affect the mobilization and removal of PTEs from HW and their presence in floc. Temperature/pressure appeared to increase PTE removal through the condensate path, although that removal had only a negligible impact on the contents of PTEs in floc. Autoclaving temperature correlated positively, although not significantly at a 95% confidence level, with the levels of Pb and Zn in floc. On the other hand, it correlated negatively with the Hg content in floc. Increasing temperature/pressure also increased the water extraction of PTEs from floc, with the exception of Cr. However, in the context of producing high quality compost, the extraction rates were too low to bring about a substantial decrease of PTEs in floc.

  14. Impact of micro- and macroelement content on potential use of freshwater sediments (gyttja) derived from lakes of eastern Latvia.

    PubMed

    Vincevica-Gaile, Zane; Stankevica, Karina

    2017-01-27

    Organic-rich freshwater sediments formed from the remains of water plants, plankton and benthic organisms, which are transformed by microorganisms, and mixed with mineral components supplied from the lake basin, are known as gyttja (sapropel or dy). Gyttja is a valuable natural resource that can be used in various fields such as agriculture, forestry, construction, chemical industry, balneology and the latter ones are especially interested in chemical composition and safety of natural materials. The aim of the study was to investigate micro- and macro-element content of gyttja derived from lakes of eastern Latvia (north-east of Europe). Depending on composition, sediment samples were identified as peaty, various algae, green algae, diatom, carbonate and organic-silicate types of gyttja. Dried samples were wet-digested by heating in HNO3/H2O2 solution until complete mineralization. Sample solutions were analysed by atomic absorption spectrometry (AAS) to detect concentration of Ca, Fe, K, Mg, Mn, Na and Zn, but inductively coupled plasma mass spectrometry (ICP-MS) was applied for As, Ba, Cd, Co, Cr, Cu, Li, Ni, Pb, Rb, Se, Sr and V concentration measurements. Total content of elements was variable; higher macroelement concentration was detected for gyttja of carbonate type, but higher microelement concentration-for organic-silicate gyttja. As concentration of several elements was much lower than permitted by the European Union legislation, gyttja is not only safe, but also highly valuable resource applicable in organic agriculture. There is a potential to use gyttja as a peloid in health care, but element bioavailability should be estimated likewise.

  15. Distribution of Phenolic Contents, Antidiabetic Potentials, Antihypertensive Properties, and Antioxidative Effects of Soursop (Annona muricata L.) Fruit Parts In Vitro

    PubMed Central

    Adefegha, Stephen A.; Oyeleye, Sunday I.; Oboh, Ganiyu

    2015-01-01

    Soursop fruit has been used in folklore for the management of type-2 diabetes and hypertension with limited information on the scientific backing. This study investigated the effects of aqueous extracts (1 : 100 w/v) of Soursop fruit part (pericarp, pulp, and seed) on key enzymes linked to type-2 diabetes (α-amylase and α-glucosidase) and hypertension [angiotensin-I converting enzyme (ACE)]. Radicals scavenging and Fe2+ chelation abilities and reducing property as well as phenolic contents of the extracts were also determined. Our data revealed that the extracts inhibited α-amylase and α-glucosidase and ACE activities dose-dependently. The effective concentration of the extract causing 50% antioxidant activity (EC50) revealed that pericarp extract had the highest α-amylase (0.46 mg/mL), α-glucosidase (0.37 mg/mL), and ACE (0.03 mg/mL) inhibitory activities while the seed extract had the least [α-amylase (0.76 mg/mL); α-glucosidase (0.73 mg/mL); and ACE (0.20 mg/mL)]. Furthermore, the extracts scavenged radicals, reduced Fe3+ to Fe2+, and chelated Fe2+. The phenolic contents in the extracts ranged from 85.65 to 560.21 mg/100 g. The enzymes inhibitory and antioxidants potentials of the extracts could be attributed to their phenolic distributions which could be among the scientific basis for their use in the management of diabetes and hypertension. However, the pericarp appeared to be most promising. PMID:26788368

  16. Redox regulation of intercellular transport.

    PubMed

    Benitez-Alfonso, Yoselin; Jackson, David; Maule, Andy

    2011-01-01

    Plant cells communicate with each other via plasmodesmata (PDs) in order to orchestrate specific responses to environmental and developmental cues. At the same time, environmental signals regulate this communication by promoting changes in PD structure that modify symplastic permeability and, in extreme cases, isolate damaged cells. Reactive oxygen species (ROS) are key messengers in plant responses to a range of biotic and abiotic stresses. They are also generated during normal metabolism, and mediate signaling pathways that modulate plant growth and developmental transitions. Recent research has suggested the participation of ROS in the regulation of PD transport. The study of several developmental and stress-induced processes revealed a co-regulation of ROS and callose (a cell wall polymer that regulates molecular flux through PDs). The identification of Arabidopsis mutants simultaneously affected in cell redox homeostasis and PD transport, and the histological detection of hydrogen peroxide and peroxidases in the PDs of the tomato vascular cambium provide new information in support of this novel regulatory mechanism. Here, we describe the evidence that supports a role for ROS in the regulation of callose deposition and/or in the formation of secondary PD, and discuss the potential importance of this mechanism during plant growth or defense against environmental stresses.

  17. Redox Reactions of Myoglobin

    PubMed Central

    2013-01-01

    Abstract Significance: Failure to maintain myoglobin (Mb) in the reduced state causes the formation of metMb, ferryl Mb species, and cross-linked Mb. Dissociation of ferriprotoporphyrin IX from the globin and release of iron atoms can also occur as oxidized Mb accumulates. These modifications may contribute to various oxidative pathologies in muscle and muscle foods. Recent Advances: The mechanism of ferryl Mb-mediated oxidative damage to nearby structures has been partially elucidated. Dissociation of ferriprotoporphyrin IX from metMb occurs more readily at acidic pH values. The dissociated ferriprotoporphyrin IX (also called hemin) readily decomposes preformed lipid hydroperoxides to reactive oxygen species. Heme oxygenase as well as lipophilic free radicals can degrade the protoporphyrin IX moiety, which results in the formation of free iron. Critical Issues: The multiple pathways by which Mb can incur toxicity create difficulties in determining the major cause of oxidative damage in a particular system. Peroxides and low pH activate each of the oxidative Mb forms, ferriprotoporphyrin IX, and released iron. Determining the relative concentration of these species is technically difficult, but essential to a complete understanding of oxidative pathology in muscle tissue. Future Directions: Improved methods to assess the different pathways of Mb toxicity are needed. Although significant advances have been made in the understanding of Mb interactions with other biomolecules, further investigation is needed to understand the physical and chemical nature of these interactions. Antioxid. Redox Signal. 18, 2342–2351. PMID:22900975

  18. Membrane development for vanadium redox flow batteries.

    PubMed

    Schwenzer, Birgit; Zhang, Jianlu; Kim, Soowhan; Li, Liyu; Liu, Jun; Yang, Zhenguo

    2011-10-17

    Large-scale energy storage has become the main bottleneck for increasing the percentage of renewable energy in our electricity grids. Redox flow batteries are considered to be among the best options for electricity storage in the megawatt range and large demonstration systems have already been installed. Although the full technological potential of these systems has not been reached yet, currently the main problem hindering more widespread commercialization is the high cost of redox flow batteries. Nafion, as the preferred membrane material, is responsible for about 11% of the overall cost of a 1 MW/8 MWh system. Therefore, in recent years two main membrane related research threads have emerged: 1) chemical and physical modification of Nafion membranes to optimize their properties with regard to vanadium redox flow battery (VRFB) application; and 2) replacement of the Nafion membranes with different, less expensive materials. This review summarizes the underlying basic scientific issues associated with membrane use in VRFBs and presents an overview of membrane-related research approaches aimed at improving the efficiency of VRFBs and making the technology cost-competitive. Promising research strategies and materials are identified and suggestions are provided on how materials issues could be overcome.

  19. Neptunium redox speciation at the illite surface

    NASA Astrophysics Data System (ADS)

    Marsac, Rémi; Banik, Nidhu lal; Lützenkirchen, Johannes; Marquardt, Christian Michael; Dardenne, Kathy; Schild, Dieter; Rothe, Joerg; Diascorn, Alexandre; Kupcik, Tomas; Schäfer, Thorsten; Geckeis, Horst

    2015-03-01

    Neptunium (Np(V)) sorption onto a purified illite is investigated as a function of pH (3-10) and [NpVO2+]tot(3 × 10-8-3 × 10-4 M) in 0.1 M NaCl under Ar atmosphere. After about one week reaction time, only insignificant variation of Np sorption is observed and the establishment of reaction equilibrium can be assumed. Surprisingly, solid-liquid distribution ratios (Rd) are clearly higher than those measured for Np(V) sorption onto illite under aerobic conditions. The observation that Rd increases with decreasing pe (pe = -log ae-) suggests partial reduction to Np(IV), although measured redox potentials (pe values) at a first glance suggest the predominance of Np(V). Reduction to Np(IV) at the illite surface could indeed be confirmed by X-ray absorption near-edge spectroscopy (XANES). Np speciation in presence of the purified Na-illite under given conditions is consistently described by applying the 2 sites protolysis non-electrostatic surface complexation and cation exchange model. Measured pe data are taken to calculate Np redox state and surface complexation constants for Np(IV) are derived by applying a data fitting procedure. Constants are very consistent with results obtained by applying an existing linear free energy relationship (LFER). Taking Np(IV) surface complexation constants into account shifts the calculated Np(V)/Np(IV) redox borderline in presence of illite surfaces by 3-5 pe units (0.2-0.3 V) towards redox neutral conditions. Our study suggests that Np(V) reduction in presence of a sorbing mineral phase is thermodynamically favored.

  20. Redox Regulation in Plant Immune Function

    PubMed Central

    Frederickson Matika, Debra E.

    2014-01-01

    Abstract Significance: Production of reactive oxygen species (ROS) and reactive nitrogen species (RNS) occurs rapidly in response to attempted pathogen invasion of potential host plants. Such reduction–oxidation (redox) changes are sensed and transmitted to engage immune function, including the hypersensitive response, a programmed execution of challenged plant cells. Recent Advances: Pathogen elicitors trigger changes in calcium that are sensed by calmodulin, calmodulin-like proteins, and calcium-dependent protein kinases, which activate ROS and RNS production. The ROS and RNS production is compartmentalized within the cell and occurs through multiple routes. Mitogen-activated protein kinase (MAPK) cascades are engaged upstream and downstream of ROS and nitric oxide (NO) production. NO is increasingly recognized as a key signaling molecule, regulating downstream protein function through S-nitrosylation, the addition of an NO moiety to a reactive cysteine thiol. Critical Issues: How multiple sources of ROS and RNS are coordinated is unclear. The putative protein sensors that detect and translate fluxes in ROS and RNS into differential gene expression are obscure. Protein tyrosine nitration following reaction of peroxynitrite with tyrosine residues has been proposed as another signaling mechanism or as a marker leading to protein degradation, but the reversibility remains to be established. Future Directions: Research is needed to identify the full spectrum of NO-modified proteins with special emphasis on redox-activated transcription factors and their cognate target genes. A systems approach will be required to uncover the complexities integral to redox regulation of MAPK cascades, transcription factors, and defense genes through the combined effects of calcium, phosphorylation, S-nitrosylation, and protein tyrosine nitration. Antioxid. Redox Signal. 21, 1373–1388. PMID:24206122

  1. Proterozoic ocean redox and biogeochemical stasis

    PubMed Central

    Reinhard, Christopher T.; Planavsky, Noah J.; Robbins, Leslie J.; Partin, Camille A.; Gill, Benjamin C.; Lalonde, Stefan V.; Bekker, Andrey; Konhauser, Kurt O.; Lyons, Timothy W.

    2013-01-01

    The partial pressure of oxygen in Earth’s atmosphere has increased dramatically through time, and this increase is thought to have occurred in two rapid steps at both ends of the Proterozoic Eon (∼2.5–0.543 Ga). However, the trajectory and mechanisms of Earth’s oxygenation are still poorly constrained, and little is known regarding attendant changes in ocean ventilation and seafloor redox. We have a particularly poor understanding of ocean chemistry during the mid-Proterozoic (∼1.8–0.8 Ga). Given the coupling between redox-sensitive trace element cycles and planktonic productivity, various models for mid-Proterozoic ocean chemistry imply different effects on the biogeochemical cycling of major and trace nutrients, with potential ecological constraints on emerging eukaryotic life. Here, we exploit the differing redox behavior of molybdenum and chromium to provide constraints on seafloor redox evolution by coupling a large database of sedimentary metal enrichments to a mass balance model that includes spatially variant metal burial rates. We find that the metal enrichment record implies a Proterozoic deep ocean characterized by pervasive anoxia relative to the Phanerozoic (at least ∼30–40% of modern seafloor area) but a relatively small extent of euxinic (anoxic and sulfidic) seafloor (less than ∼1–10% of modern seafloor area). Our model suggests that the oceanic Mo reservoir is extremely sensitive to perturbations in the extent of sulfidic seafloor and that the record of Mo and chromium enrichments through time is consistent with the possibility of a Mo–N colimited marine biosphere during many periods of Earth’s history. PMID:23515332

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

    NASA Astrophysics Data System (ADS)

    Mansfeldt, T.; Overesch, M.

    2009-04-01

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

  3. Differentiating cancerous from normal breast tissue by redox imaging

    NASA Astrophysics Data System (ADS)

    Xu, He N.; Tchou, Julia; Feng, Min; Zhao, Huaqing; Li, Lin Z.

    2015-02-01

    Abnormal metabolism can be a hallmark of cancer occurring early before detectable histological changes and may serve as an early detection biomarker. The current gold standard to establish breast cancer (BC) diagnosis is histological examination of biopsy. Previously we have found that pre-cancer and cancer tissues in animal models displayed abnormal mitochondrial redox state. Our technique of quantitatively measuring the mitochondrial redox state has the potential to be implemented as an early detection tool for cancer and may provide prognostic value. We therefore in this present study, investigated the feasibility of quantifying the redox state of tumor samples from 16 BC patients. Tumor tissue aliquots were collected from both normal and cancerous tissue from the affected cancer-bearing breasts of 16 female patients (5 TNBC, 9 ER+, 2 ER+/Her2+) shortly after surgical resection. All specimens were snap-frozen with liquid nitrogen on site and scanned later with the Chance redox scanner, i.e., the 3D cryogenic NADH/oxidized flavoprotein (Fp) fluorescence imager. Our preliminary results showed that both NADH and Fp (including FAD, i.e., flavin adenine dinucleotide) signals in the cancerous tissues roughly tripled to quadrupled those in the normal tissues (p<0.05) and the redox ratio Fp/(NADH+Fp) was about 27% higher in the cancerous tissues than in the normal ones (p<0.05). Our findings suggest that the redox state could differentiate between cancer and non-cancer breast tissues in human patients and this novel redox scanning procedure may assist in tissue diagnosis in freshly procured biopsy samples prior to tissue fixation. We are in the process of evaluating the prognostic value of the redox imaging indices for BC.

  4. Evaluation of Phenolic Content Variability along with Antioxidant, Antimicrobial, and Cytotoxic Potential of Selected Traditional Medicinal Plants from India

    PubMed Central

    Singh, Garima; Passsari, Ajit K.; Leo, Vincent V.; Mishra, Vineet K.; Subbarayan, Sarathbabu; Singh, Bhim P.; Kumar, Brijesh; Kumar, Sunil; Gupta, Vijai K.; Lalhlenmawia, Hauzel; Nachimuthu, Senthil K.

    2016-01-01

    Plants have been used since ancient times as an important source of biologically active substances. The aim of the present study was to investigate the phytochemical constituents (flavonoids and phenolics), antioxidant potential, cytotoxicity against HepG2 (human hepato carcinoma) cancer cell lines, and the antimicrobial activity of the methanol extract of selected traditional medicinal plants collected from Mizoram, India. A number of phenolic compounds were detected using HPLC-DAD-ESI-TOF-MS, mainly Luteolin, Kaempferol, Myricetin, Gallic Acid, Quercetin and Rutin, some of which have been described for the first time in the selected plants. The total phenolic and flavonoid contents showed high variation ranging from 4.44 to 181.91 μg of Gallic Acid equivalent per milligram DW (GAE/mg DW) and 3.17 to 102.2 μg of Quercetin/mg, respectively. The antioxidant capacity was determined by DPPH (IC50 values ranges from 34.22 to 131.4 μg/mL), ABTS (IC50 values ranges from 24.08 to 513.4 μg/mL), and reducing power assays. Antimicrobial activity was assayed against gram positive (Staphylococcus aureus), gram negative (Escherichia coli, Pseudomonas aeruginosa), and yeast (Candida albicans) demonstrating that the methanol extracts of some plants were efficacious antimicrobial agents. Additionally, cytotoxicity was assessed on human hepato carcinoma (HepG2) cancer cell lines and found that the extracts of Albizia lebbeck, Dillenia indica, and Bombax ceiba significantly decreased the cell viability at low concentrations with IC50 values of 24.03, 25.09, and 29.66 μg/mL, respectively. This is the first report of detection of phenolic compounds along with antimicrobial, antioxidant and cytotoxic potential of selected medicinal plants from India, which indicates that these plants might be valuable source for human and animal health. PMID:27066046

  5. Evaluation of Phenolic Content Variability along with Antioxidant, Antimicrobial, and Cytotoxic Potential of Selected Traditional Medicinal Plants from India.

    PubMed

    Singh, Garima; Passsari, Ajit K; Leo, Vincent V; Mishra, Vineet K; Subbarayan, Sarathbabu; Singh, Bhim P; Kumar, Brijesh; Kumar, Sunil; Gupta, Vijai K; Lalhlenmawia, Hauzel; Nachimuthu, Senthil K

    2016-01-01

    Plants have been used since ancient times as an important source of biologically active substances. The aim of the present study was to investigate the phytochemical constituents (flavonoids and phenolics), antioxidant potential, cytotoxicity against HepG2 (human hepato carcinoma) cancer cell lines, and the antimicrobial activity of the methanol extract of selected traditional medicinal plants collected from Mizoram, India. A number of phenolic compounds were detected using HPLC-DAD-ESI-TOF-MS, mainly Luteolin, Kaempferol, Myricetin, Gallic Acid, Quercetin and Rutin, some of which have been described for the first time in the selected plants. The total phenolic and flavonoid contents showed high variation ranging from 4.44 to 181.91 μg of Gallic Acid equivalent per milligram DW (GAE/mg DW) and 3.17 to 102.2 μg of Quercetin/mg, respectively. The antioxidant capacity was determined by DPPH (IC50 values ranges from 34.22 to 131.4 μg/mL), ABTS (IC50 values ranges from 24.08 to 513.4 μg/mL), and reducing power assays. Antimicrobial activity was assayed against gram positive (Staphylococcus aureus), gram negative (Escherichia coli, Pseudomonas aeruginosa), and yeast (Candida albicans) demonstrating that the methanol extracts of some plants were efficacious antimicrobial agents. Additionally, cytotoxicity was assessed on human hepato carcinoma (HepG2) cancer cell lines and found that the extracts of Albizia lebbeck, Dillenia indica, and Bombax ceiba significantly decreased the cell viability at low concentrations with IC50 values of 24.03, 25.09, and 29.66 μg/mL, respectively. This is the first report of detection of phenolic compounds along with antimicrobial, antioxidant and cytotoxic potential of selected medicinal plants from India, which indicates that these plants might be valuable source for human and animal health.

  6. Mantle–slab interaction and redox mechanism of diamond formation

    PubMed Central

    Palyanov, Yuri N.; Bataleva, Yuliya V.; Sokol, Alexander G.; Borzdov, Yuri M.; Kupriyanov, Igor N.; Reutsky, Vadim N.; Sobolev, Nikolai V.

    2013-01-01

    Subduction tectonics imposes an important role in the evolution of the interior of the Earth and its global carbon cycle; however, the mechanism of the mantle–slab interaction remains unclear. Here, we demonstrate the results of high-pressure redox-gradient experiments on the interactions between Mg-Ca-carbonate and metallic iron, modeling the processes at the mantle–slab boundary; thereby, we present mechanisms of diamond formation both ahead of and behind the redox front. It is determined that, at oxidized conditions, a low-temperature Ca-rich carbonate melt is generated. This melt acts as both the carbon source and crystallization medium for diamond, whereas at reduced conditions, diamond crystallizes only from the Fe-C melt. The redox mechanism revealed in this study is used to explain the contrasting heterogeneity of natural diamonds, as seen in the composition of inclusions, carbon isotopic composition, and nitrogen impurity content. PMID:24297876

  7. Nrf2 and Redox Status in Prediabetic and Diabetic Patients

    PubMed Central

    Jiménez-Osorio, Angélica S.; Picazo, Alejandra; González-Reyes, Susana; Barrera-Oviedo, Diana; Rodríguez-Arellano, Martha E.; Pedraza-Chaverri, José

    2014-01-01

    The redox status associated with nuclear factor erythroid 2-related factor-2 (Nrf2) was evaluated in prediabetic and diabetic subjects. Total antioxidant status (TAS) in plasma and erythrocytes, glutathione (GSH) and malondialdehyde (MDA) content and activity of antioxidant enzymes were measured as redox status markers in 259 controls, 111 prediabetics and 186 diabetic type 2 subjects. Nrf2 was measured in nuclear extract fractions from peripheral blood mononuclear cells (PBMC). Nrf2 levels were lower in prediabetic and diabetic patients. TAS, GSH and activity of glutamate cysteine ligase were lower in diabetic subjects. An increase of MDA and superoxide dismutase activity was found in diabetic subjects. These results suggest that low levels of Nrf2 are involved in the development of oxidative stress and redox status disbalance in diabetic patients. PMID:25383674

  8. CO2 content of andesitic melts at graphite-saturated upper mantle conditions with implications for redox state of oceanic basalt source regions and remobilization of reduced carbon from subducted eclogite

    NASA Astrophysics Data System (ADS)

    Eguchi, James; Dasgupta, Rajdeep

    2017-03-01

    We have performed experiments to determine the effects of pressure, temperature and oxygen fugacity on the CO2 contents in nominally anhydrous andesitic melts at graphite saturation. The andesite composition was specifically chosen to match a low-degree partial melt composition that is generated from MORB-like eclogite in the convective, oceanic upper mantle. Experiments were performed at 1-3 GPa, 1375-1550 °C, and fO2 of FMQ -3.2 to FMQ -2.3 and the resulting experimental glasses were analyzed for CO2 and H2O contents using FTIR and SIMS. Experimental results were used to develop a thermodynamic model to predict CO2 content of nominally anhydrous andesitic melts at graphite saturation. Fitting of experimental data returned thermodynamic parameters for dissolution of CO2 as molecular CO2: ln( K 0) = -21.79 ± 0.04, Δ V 0 = 32.91 ± 0.65 cm3mol-1, Δ H 0 = 107 ± 21 kJ mol-1, and dissolution of CO2 as CO3 2-: ln (K 0 ) = -21.38 ± 0.08, Δ V 0 = 30.66 ± 1.33 cm3 mol-1, Δ H 0 = 42 ± 37 kJ mol-1, where K 0 is the equilibrium constant at some reference pressure and temperature, Δ V 0 is the volume change of reaction, and Δ H 0 is the enthalpy change of reaction. The thermodynamic model was used along with trace element partition coefficients to calculate the CO2 contents and CO2/Nb ratios resulting from the mixing of a depleted MORB and the partial melt of a graphite-saturated eclogite. Comparison with natural MORB and OIB data suggests that the CO2 contents and CO2/Nb ratios of CO2-enriched oceanic basalts cannot be produced by mixing with partial melts of graphite-saturated eclogite. Instead, they must be produced by melting of a source containing carbonate. This result places a lower bound on the oxygen fugacity for the source region of these CO2-enriched basalts, and suggests that fO2 measurements made on cratonic xenoliths may not be applicable to the convecting upper mantle. CO2-depleted basalts, on the other hand, are consistent with mixing between

  9. Redox Pioneer: Professor Helmut Sies

    PubMed Central

    Radi, Rafael

    2014-01-01

    Abstract Professor Helmut Sies Dr. Helmut Sies (MD, 1967) is recognized as a Redox Pioneer, because he authored five articles on oxidative stress, lycopene, and glutathione, each of which has been cited more than 1000 times, and coauthored an article on hydroperoxide metabolism in mammalian systems cited more than 5000 times (Google Scholar). He obtained preclinical education at the University of Tübingen and the University of Munich, clinical training at Munich (MD, 1967) and Paris, and completed Habilitation at Munich (Physiological Chemistry and Physical Biochemistry, 1972). In early research, he first identified hydrogen peroxide (H2O2) as a normal aerobic metabolite and devised a method to quantify H2O2 concentration and turnover in cells. He quantified central redox systems for energy metabolism (NAD, NADP systems) and antioxidant GSH in subcellular compartments. He first described ebselen, a selenoorganic compound, as a glutathione peroxidase mimic. He contributed a fundamental discovery to the physiology of GSH, selenium nutrition, singlet oxygen biochemistry, and health benefits of dietary lycopene and cocoa flavonoids. He has published more than 600 articles, 134 of which are cited at least 100 times, and edited 28 books. His h-index is 115. During the last quarter of the 20th century and well into the 21st, he has served as a scout, trailblazer, and pioneer in redox biology. His formulation of the concept of oxidative stress stimulated and guided research in oxidants and antioxidants; his pioneering research on carotenoids and flavonoids informed nutritional strategies against cancer, cardiovascular disease, and aging; and his quantitative approach to redox biochemistry provides a foundation for modern redox systems biology. Helmut Sies is a true Redox Pioneer. Antioxid. Redox Signal. 21, 2459–2468. The joy of exploring the unknown and finding something novel and noteworthy: what a privilege! —Prof. Helmut Sies PMID:25178739

  10. Voltage clustering in redox-active ligand complexes: mitigating electronic communication through choice of metal ion

    SciTech Connect

    Zarkesh, Ryan A.; Ichimura, Andrew S.; Monson, Todd C.; Tomson, Neil C.; Anstey, Mitchell R.

    2016-02-01

    We used the redox-active bis(imino)acenapthene (BIAN) ligand to synthesize homoleptic aluminum, chromium, and gallium complexes of the general formula (BIAN)3M. The resulting compounds were characterized using X-ray crystallography, NMR, EPR, magnetic susceptibility and cyclic voltammetry measurements and modeled using both DFT and ab initio wavefunction calculations to compare the orbital contributions of main group elements and transition metals in ligand-based redox events. Ultimately, complexes of this type have the potential to improve the energy density and electrolyte stability of grid-scale energy storage technologies, such as redox flow batteries, through thermodynamically-clustered redox events.

  11. Voltage clustering in redox-active ligand complexes: mitigating electronic communication through choice of metal ion

    DOE PAGES

    Zarkesh, Ryan A.; Ichimura, Andrew S.; Monson, Todd C.; ...

    2016-02-01

    We used the redox-active bis(imino)acenapthene (BIAN) ligand to synthesize homoleptic aluminum, chromium, and gallium complexes of the general formula (BIAN)3M. The resulting compounds were characterized using X-ray crystallography, NMR, EPR, magnetic susceptibility and cyclic voltammetry measurements and modeled using both DFT and ab initio wavefunction calculations to compare the orbital contributions of main group elements and transition metals in ligand-based redox events. Ultimately, complexes of this type have the potential to improve the energy density and electrolyte stability of grid-scale energy storage technologies, such as redox flow batteries, through thermodynamically-clustered redox events.

  12. Electronic Tongue Containing Redox and Conductivity Sensors

    NASA Technical Reports Server (NTRS)

    Buehler, Martin

    2007-01-01

    The Electronic Tongue (E-tongue 2) is an assembly of sensors for measuring concentrations of metal ions and possibly other contaminants in water. Potential uses for electronic tongues include monitoring the chemical quality of water in a variety of natural, industrial, and laboratory settings, and detecting micro-organisms indirectly by measuring microbially influenced corrosion. The device includes a heater, a temperature sensor, an oxidation/reduction (redox) sensor pair, an electrical sensor, an array of eight galvanic cells, and eight ion-specific electrodes.

  13. Redox polymer mediation for enzymatic biofuel cells

    NASA Astrophysics Data System (ADS)

    Gallaway, Joshua

    Mediated biocatalytic cathodes prepared from the oxygen-reducing enzyme laccase and redox-conducting osmium hydrogels were characterized for use as cathodes in enzymatic biofuel cells. A series of osmium-based redox polymers was synthesized with redox potentials spanning the range from 0.11 V to 0.85 V (SHE), and the resulting biocatalytic electrodes were modeled to determine reaction kinetic constants using the current response, measured osmium concentration, and measured apparent electron diffusion. As in solution-phase systems, the bimolecular rate constant for mediation was found to vary greatly with mediator potential---from 250 s-1M-1 when mediator and enzyme were close in potential to 9.4 x 10 4 s-1M-1 when this overpotential was large. Optimum mediator potential for a cell operating with a non-limiting platinum anode and having no mass transport limitation from bulk solution was found to be 0.66 V (SHE). Redox polymers were synthesized under different concentrations, producing osmium variation. An increase from 6.6% to 7.2% osmium increased current response from 1.2 to 2.1 mA/cm2 for a planar film in 40°C oxygen-saturated pH 4 buffer, rotating at 900 rpm. These results translated to high surface area electrodes, nearly doubling current density to 13 mA/cm2, the highest to date for such an electrode. The typical fungal laccase from Trametes versicolor was replaced by a bacterially-expressed small laccase from Streptomyces coelicolor, resulting in biocatalytic films that reduced oxygen at increased pH, with full functionality at pH 7, producing 1.5 mA/cm 2 in planar configuration. Current response was biphasic with pH, matching the activity profile of the free enzyme in solution. The mediated enzyme electrode system was modeled with respect to apparent electron diffusion, mediator concentration, and transport of oxygen from bulk solution, all of which are to some extent controlled by design. Each factor was found to limit performance in certain circumstances

  14. Influence of macrophage migration inhibitory factor (MIF) on the zinc content and redox state of protein-bound sulphydryl groups in rat sperm: indications for a new role of MIF in sperm maturation.

    PubMed

    Eickhoff, Regina; Baldauf, Christina; Koyro, Hans-Werner; Wennemuth, Gunther; Suga, Yasushi; Seitz, Jürgen; Henkel, Ralf; Meinhardt, Andreas

    2004-08-01

    The function of macrophage migration inhibitory factor (MIF) in sperm maturation was studied by investigating its role in the biochemical maturation of the outer dense fibres. Rat sperm obtained from the caput and cauda epididymis were stimulated overnight with either recombinant MIF or MIF-containing vesicles originating from epididymal fluid at various concentrations. The zinc content of both the sperm and the medium was determined by means of atomic absorption spectrometry. Incubation in both recombinant MIF and vesicular MIF resulted in a statistically significant decrease of the zinc content in stimulated caput sperm of approximately 50%. In parallel, the conditioned media showed a clear increase in the concentration of this trace metal. The effect of MIF was less marked in cauda sperm. In addition, we demonstrated a statistically significant increase of detectable free thiol groups in the sperm mid- and principle piece in isolated rat sperm after stimulation with MIF at concentrations of 25 and 50 ng/ml. Our data suggest that MIF plays an important role in the maturation process of rat sperm during epididymal transit by inducing the elimination of zinc and affecting the amount of free sulphydryl groups in the sperm flagella.

  15. Electroanalytical measurements without electrolytes: conducting polymers as probes for redox titration in non-conductive organic media.

    PubMed

    Lange, Ulrich; Mirsky, Vladimir M

    2012-09-26

    Electroanalytical methods have been applied only in conducting media. An application of conducting polymers allows to overcome this limitation. If such material is in electrochemical equilibrium with dissolved redox active species, its electrical conductivity depends on the redox potential of these species. Therefore, conductometric measurements with conducting polymers can provide about the same information as classical redox electrodes. The approach was applied for redox titration. Equivalent points obtained by this titration in aqueous and organic electrolytes were identical. Then the approach was applied for determination of bromine number by redox titration in non-conducting organic phase.

  16. Redox electrode materials for supercapatteries

    NASA Astrophysics Data System (ADS)

    Yu, Linpo; Chen, George Z.

    2016-09-01

    Redox electrode materials, including transition metal oxides and electronically conducting polymers, are capable of faradaic charge transfer reactions, and play important roles in most electrochemical energy storage devices, such as supercapacitor, battery and supercapattery. Batteries are often based on redox materials with low power capability and safety concerns in some cases. Supercapacitors, particularly those based on redox inactive materials, e.g. activated carbon, can offer high power output, but have relatively low energy capacity. Combining the merits of supercapacitor and battery into a hybrid, the supercapattery can possess energy as much as the battery and output a power almost as high as the supercapacitor. Redox electrode materials are essential in the supercapattery design. However, it is hard to utilise these materials easily because of their intrinsic characteristics, such as the low conductivity of metal oxides and the poor mechanical strength of conducting polymers. This article offers a brief introduction of redox electrode materials, the basics of supercapattery and its relationship with pseudocapacitors, and reviews selectively some recent progresses in the relevant research and development.

  17. Thiol-based Redox Proteins in Brassica napus Guard Cell Abscisic Acid and Methyl Jasmonate Signaling

    PubMed Central

    Zhu, Mengmeng; Zhu, Ning; Song, Wen-yuan; Harmon, Alice C.; Assmann, Sarah M.; Chen, Sixue

    2014-01-01

    SUMMARY Reversibly oxidized cysteine sulfhydryl groups serve as redox sensors or targets of redox sensing that are important in different physiological processes. Little is known, however, about redox sensitive proteins in guard cells and how they function in stomatal signaling. In this study, Brassica napus guard cell proteins altered by redox in response to abscisic acid (ABA) or methyl jasmonate (MeJA) were identified by complementary proteomics approaches, saturation differential in-gel electrophoresis (DIGE) and isotope-coded affinity tag (ICAT). In total, 65 and 118 potential redox responsive proteins were identified in ABA and MeJA treated guard cells, respectively. All the proteins contain at least one cysteine, and over half of them are predicted to form intra-molecular disulfide bonds. Most of the proteins fall into the functional groups of energy, stress and defense, and metabolism. Based on the peptide sequences identified by mass spectrometry, 30 proteins were common to ABA and MeJA treated samples. A total of 44 cysteines was mapped in all the identified proteins, and their levels of redox sensitivity were quantified. Two of the proteins, a SNRK2 kinase and an isopropylmalate dehydrogenase were confirmed to be redox regulated and involved in stomatal movement. This study creates an inventory of potential redox switches, and highlights a protein redox regulatory mechanism in guard cell ABA and MeJA signal transduction. PMID:24580573

  18. Quantifying blue and green virtual water contents in global crop production as well as potential production losses without irrigation

    NASA Astrophysics Data System (ADS)

    Siebert, Stefan; Döll, Petra

    2010-04-01

    SummaryCrop production requires large amounts of green and blue water. We developed the new global crop water model GCWM to compute consumptive water use (evapotranspiration) and virtual water content (evapotranspiration per harvested biomass) of crops at a spatial resolution of 5' by 5', distinguishing 26 crop classes, and blue versus green water. GCWM is based on the global land use data set MIRCA2000 that provides monthly growing areas for 26 crop classes under rainfed and irrigated conditions for the period 1998-2002 and represents multi-cropping. By computing daily soil water balances, GCWM determines evapotranspiration of blue and green water for each crop and grid cell. Cell-specific crop production under both rainfed and irrigated conditions is computed by downscaling average crop yields reported for 402 national and sub-national statistical units, relating rainfed and irrigated crop yields reported in census statistics to simulated ratios of actual to potential crop evapotranspiration for rainfed crops. By restricting water use of irrigated crops to green water only, the potential production loss without any irrigation was computed. For the period 1998-2002, the global value of total crop water use was 6685 km 3 yr -1, of which blue water use was 1180 km 3 yr -1, green water use of irrigated crops was 919 km 3 yr -1 and green water use of rainfed crops was 4586 km 3 yr -1. Total crop water use was largest for rice (941 km 3 yr -1), wheat (858 km 3 yr -1) and maize (722 km 3 yr -1). The largest amounts of blue water were used for rice (307 km 3 yr -1) and wheat (208 km 3 yr -1). Blue water use as percentage of total crop water use was highest for date palms (85%), cotton (39%), citrus fruits (33%), rice (33%) and sugar beets (32%), while for cassava, oil palm and cocoa, almost no blue water was used. Average crop yield of irrigated cereals was 442 Mg km -2 while average yield of rainfed cereals was only 266 Mg km -2. Average virtual water content of cereal

  19. Vascular remodeling: A redox-modulated mechanism of vessel caliber regulation.

    PubMed

    Tanaka, Leonardo Y; Laurindo, Francisco R M

    2017-01-18

    Vascular remodeling, i.e. whole-vessel structural reshaping, determines lumen caliber in (patho)physiology. Here we review mechanisms underlying vessel remodeling, with emphasis in redox regulation. First, we discuss confusing terminology and focus on strictu sensu remodeling. Second, we propose a mechanobiological remodeling paradigm based on the concept of tensional homeostasis as a setpoint regulator. We first focus on shear-mediated models as prototypes of remodeling closely dominated by highly redox-sensitive endothelial function. More detailed discussions focus on mechanosensors, integrins, extracellular matrix, cytoskeleton and inflammatory pathways as potential of mechanisms potentially coupling tensional homeostasis to redox regulation. Further discussion of remodeling associated with atherosclerosis and injury repair highlights important aspects of redox vascular responses. While neointima formation has not shown consistent responsiveness to antioxidants, vessel remodeling has been more clearly responsive, indicating that despite the multilevel redox signaling pathways, there is a coordinated response of the whole vessel. Among mechanisms that may orchestrate redox pathways, we discuss roles of superoxide dismutase activity and extracellular protein disulfide isomerase. We then discuss redox modulation of aneurysms, a special case of expansive remodeling. We propose that the redox modulation of vascular remodeling may reflect (1) remodeling pathophysiology is dominated by a particularly redox-sensitive cell type, e.g., endothelial cells (2) redox pathways are temporospatially coordinated at an organ level across distinct cellular and acellular structures or (3) the tensional homeostasis setpoint is closely connected to redox signaling. The mechanobiological/redox model discussed here can be a basis for improved understanding of remodeling and helps clarifying mechanisms underlying prevalent hard-to-treat diseases.

  20. NMR techniques for determination of lipid content in microalgal biomass and their use in monitoring the cultivation with biodiesel potential.

    PubMed

    Sarpal, Amarjit S; Teixeira, Cláudia M L L; Silva, Paulo Roque Martins; da Costa Monteiro, Thays Vieira; da Silva, Júlia Itacolomy; da Cunha, Valnei Smarcaro; Daroda, Romeu José

    2016-03-01

    In the present investigation, the application of NMR spectroscopic techniques was extensively used with an objective to explore the biodiesel potential of biomass cultivated on a lab scale using strains of Chlorella vulgaris and Scenedesmus ecornis. The effect of variation in the composition of culturing medium on the neutral and polar lipids productivity, and fatty acid profile of solvent extracts of microalgae biomass was studied. Determination of unsaturated fatty acid composition (C18:N = 1-3, ω3 C20:5, ω3 C22:6), polyunsaturated fatty esters (PUFEs), saturated fatty acids (SFAs), unsaturated fatty acids (UFAs), free fatty acids (FFAs), and iodine value were achieved from a single (1)H NMR spectral analysis. The results were validated by (13)C NMR and GC-MS analyses. It was demonstrated that newly developed methods based on (1)H and (13)C NMR techniques are direct, rapid, and convenient for monitoring the microalgae cultivation process for enhancement of lipid productivity and their quality aspects in the solvent extracts of microalgal biomasses without any sample treatment and prior separation compared to other methods. The fatty acid composition of algae extracts was found to be similar to vegetable and fish oils, mostly rich in C16:0, C18:N (N = 0 to 3), and n-3 omega polyunsaturated fatty acids (PUFAs). The lipid content, particularly neutral lipids, as well as most of the quality parameters were found to be medium specific by both the strains. The newly developed methods based on NMR and ultrasonic procedure developed for efficient extraction of neutral lipids are cost economic and can be an effective aid for rapid screening of algae strains for modulation of lipid productivity with desired biodiesel quality and value-added products including fatty acid profile.

  1. An investigation of trends in precious metal and copper content of RAM modules in WEEE: Implications for long term recycling potential.

    PubMed

    Charles, Rhys Gareth; Douglas, Peter; Hallin, Ingrid Liv; Matthews, Ian; Liversage, Gareth

    2017-02-01

    Precious metal (PM) and copper content of dynamic-RAM modules placed on the market during 1991-2008 has been analysed by AAS following comminution and acid digestion. Linear regression analysis of compositional data ordered according to sample chronology was used to identify historic temporal trends in module composition resulting from changes in manufacturing practices, and to project future trends for use in more accurate assessment of future recycling potential. DRAM was found to be 'high grade' waste with: stable levels of gold and silver over time; 80% reduction in palladium content during 1991-2008; and 0.23g/module/year increase in copper content with a 75% projected increase from 2008 by 2020. The accuracy of future recycling potential projections for WEEE using current methods based on static compositional data from current devices is questionable due to likely changes in future device composition. The impact on recycling potential projections of waste laptops, smart phones, cell phones and tablets arising in Europe in 2020 resulting from a 75% increase in copper content is considered against existing projections using static compositional data. The results highlight that failing to consider temporal variations in PM content may result in significant discrepancies between projections and future recycling potential.

  2. Mouse redox histology using genetically encoded probes.

    PubMed

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

    2016-03-15

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

  3. 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.

  4. 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

  5. Redox regulation of mammalian sperm capacitation

    PubMed Central

    O’Flaherty, Cristian

    2015-01-01

    Capacitation is a series of morphological and metabolic changes necessary for the spermatozoon to achieve fertilizing ability. One of the earlier happenings during mammalian sperm capacitation is the production of reactive oxygen species (ROS) that will trigger and regulate a series of events including protein phosphorylation, in a time-dependent fashion. The identity of the sperm oxidase responsible for the production of ROS involved in capacitation is still elusive, and several candidates are discussed in this review. Interestingly, ROS-induced ROS formation has been described during human sperm capacitation. Redox signaling during capacitation is associated with changes in thiol groups of proteins located on the plasma membrane and subcellular compartments of the spermatozoon. Both, oxidation of thiols forming disulfide bridges and the increase on thiol content are necessary to regulate different sperm proteins associated with capacitation. Reducing equivalents such as NADH and NADPH are necessary to support capacitation in many species including humans. Lactate dehydrogenase, glucose-6-phospohate dehydrogenase, and isocitrate dehydrogenase are responsible in supplying NAD (P) H for sperm capacitation. Peroxiredoxins (PRDXs) are newly described enzymes with antioxidant properties that can protect mammalian spermatozoa; however, they are also candidates for assuring the regulation of redox signaling required for sperm capacitation. The dysregulation of PRDXs and of enzymes needed for their reactivation such as thioredoxin/thioredoxin reductase system and glutathione-S-transferases impairs sperm motility, capacitation, and promotes DNA damage in spermatozoa leading to male infertility. PMID:25926608

  6. Paraquat-Melanin Redox-Cycling: Evidence from Electrochemical Reverse Engineering.

    PubMed

    Kim, Eunkyoung; Leverage, W Taylor; Liu, Yi; Panzella, Lucia; Alfieri, Maria Laura; Napolitano, Alessandra; Bentley, William E; Payne, Gregory F

    2016-08-17

    Parkinson's disease is a neurodegenerative disorder associated with oxidative stress and the death of melanin-containing neurons of the substantia nigra. Epidemiological evidence links exposure to the pesticide paraquat (PQ) to Parkinson's disease, and this link has been explained by a redox cycling mechanism that induces oxidative stress. Here, we used a novel electrochemistry-based reverse engineering methodology to test the hypothesis that PQ can undergo reductive redox cycling with melanin. In this method, (i) an insoluble natural melanin (from Sepia melanin) and a synthetic model melanin (having a cysteinyldopamine-melanin core and dopamine-melanin shell) were entrapped in a nonconducting hydrogel film adjacent to an electrode, (ii) the film-coated electrode was immersed in solutions containing PQ (putative redox cycling reductant) and a redox cycling oxidant (ferrocene dimethanol), (iii) sequences of input potentials (i.e., voltages) were imposed to the underlying electrode to systematically engage reductive and oxidative redox cycling, and (iv) output response currents were analyzed for signatures of redox cycling. The response characteristics of the PQ-melanin systems to various input potential sequences support the hypothesis that PQ can directly donate electrons to melanin. This observation of PQ-melanin redox interactions demonstrates an association between two components that have been individually linked to oxidative stress and Parkinson's disease. Potentially, melanin's redox activity could be an important component in understanding the etiology of neurological disorders such as Parkinson's disease.

  7. Pyruvate dehydrogenase complex and nicotinamide nucleotide transhydrogenase constitute an energy consuming redox circuit

    PubMed Central

    Fisher-Wellman, Kelsey H.; Lin, Chien-Te; Ryan, Terence E.; Reese, Lauren R.; Gilliam, Laura A. A.; Cathey, Brook L.; Lark, Daniel S.; Smith, Cody D.; Muoio, Deborah M.; Neufer, P. Darrell

    2015-01-01

    SUMMARY Cellular proteins rely on reversible redox reactions to establish and maintain biological structure and function. How redox catabolic (NAD+:NADH) and anabolic (NADP+:NADPH) processes integrate during metabolism to maintain cellular redox homeostasis however is unknown. The present work identifies a continuously cycling, mitochondrial membrane potential-dependent redox circuit between the pyruvate dehydrogenase complex (PDHC) and nicotinamide nucleotide transhydrogenase (NNT). PDHC is shown to produce H2O2 in relation to reducing pressure within the complex. The H2O2 produced however is effectively masked by a continuously cycling redox circuit that links, via glutathione/thioredoxin, to NNT, which catalyzes the regeneration of NADPH from NADH at the expense of the mitochondrial membrane potential. The net effect is an automatic fine tuning of NNT-mediated energy expenditure to metabolic balance at the level of PDHC. In mitochondria, genetic or pharmacological disruptions in the PDHC-NNT redox circuit negate counterbalance changes in energy expenditure. At the whole animal level, mice lacking functional NNT (C57BL/6J) are characterized by lower energy expenditure rates, consistent with their well known susceptibility to diet-induced obesity. These findings suggest the integration of redox sensing of metabolic balance with compensatory changes in energy expenditure provides a potential mechanism by which cellular redox homeostasis is maintained and body weight is defended during periods of positive and negative energy balance. PMID:25643703

  8. Redox-gated electron transport in electrically wired ferrocene molecules

    NASA Astrophysics Data System (ADS)

    Xiao, Xiaoyin; Brune, Daniel; He, Jin; Lindsay, Stuart; Gorman, Christopher B.; Tao, Nongjian

    2006-07-01

    We have synthesized cysteamine-terminated ferrocene molecules and determined the dependence of the electron transport properties of the molecules on their redox states by measuring the current through the molecules as a function of the electrode potential. The current fluctuates over a large range, but its average value increases with the potential. We attribute the current fluctuation and its increase with the potential to the switching of the molecules from low-conductance reduced state to high-conductance oxidized state.

  9. Lowering N2O emissions from soils using eucalypt biochar: the importance of redox reactions

    NASA Astrophysics Data System (ADS)

    Quin, P.; Joseph, S.; Husson, O.; Donne, S.; Mitchell, D.; Munroe, P.; Phelan, D.; Cowie, A.; van Zwieten, L.

    2015-11-01

    Agricultural soils are the primary anthropogenic source of atmospheric nitrous oxide (N2O), contributing to global warming and depletion of stratospheric ozone. Biochar addition has shown potential to lower soil N2O emission, with the mechanisms remaining unclear. We incubated eucalypt biochar (550 °C) - 0, 1 and 5% (w/w) in Ferralsol at 3 water regimes (12, 39 and 54% WFPS) - in a soil column, following gamma irradiation. After N2O was injected at the base of the soil column, in the 0% biochar control 100% of expected injected N2O was released into headspace, declining to 67% in the 5% amendment. In a 100% biochar column at 6% WFPS, only 16% of the expected N2O was observed. X-ray photoelectron spectroscopy identified changes in surface functional groups suggesting interactions between N2O and the biochar surfaces. We have shown increases in -O-C = N /pyridine pyrrole/NH3, suggesting reactions between N2O and the carbon (C) matrix upon exposure to N2O. With increasing rates of biochar application, higher pH adjusted redox potentials were observed at the lower water contents. Evidence suggests that biochar has taken part in redox reactions reducing N2O to dinitrogen (N2), in addition to adsorption of N2O.

  10. Lowering N2O emissions from soils using eucalypt biochar: the importance of redox reactions

    PubMed Central

    Quin, P; Joseph, S; Husson, O; Donne, S; Mitchell, D; Munroe, P; Phelan, D; Cowie, A; Van Zwieten, L

    2015-01-01

    Agricultural soils are the primary anthropogenic source of atmospheric nitrous oxide (N2O), contributing to global warming and depletion of stratospheric ozone. Biochar addition has shown potential to lower soil N2O emission, with the mechanisms remaining unclear. We incubated eucalypt biochar (550 °C) – 0, 1 and 5% (w/w) in Ferralsol at 3 water regimes (12, 39 and 54% WFPS) – in a soil column, following gamma irradiation. After N2O was injected at the base of the soil column, in the 0% biochar control 100% of expected injected N2O was released into headspace, declining to 67% in the 5% amendment. In a 100% biochar column at 6% WFPS, only 16% of the expected N2O was observed. X-ray photoelectron spectroscopy identified changes in surface functional groups suggesting interactions between N2O and the biochar surfaces. We have shown increases in -O-C = N /pyridine pyrrole/NH3, suggesting reactions between N2O and the carbon (C) matrix upon exposure to N2O. With increasing rates of biochar application, higher pH adjusted redox potentials were observed at the lower water contents. Evidence suggests that biochar has taken part in redox reactions reducing N2O to dinitrogen (N2), in addition to adsorption of N2O. PMID:26615820

  11. 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

  12. Chemical Principles Revisited. Redox Reactions and the Electropotential Axis.

    ERIC Educational Resources Information Center

    Vella, Alfred J.

    1990-01-01

    This paper suggests a nontraditional pedagogic approach to the subject of redox reactions and electrode potentials suitable for freshman chemistry. Presented is a method for the representation of galvanic cells without the introduction of the symbology and notation of conventional cell diagrams. (CW)

  13. Redox heterogeneity of subsurface waters in the Mesoproterozoic ocean.

    PubMed

    Sperling, E A; Rooney, A D; Hays, L; Sergeev, V N; Vorob'eva, N G; Sergeeva, N D; Selby, D; Johnston, D T; Knoll, A H

    2014-09-01

    A substantial body of evidence suggests that subsurface water masses in mid-Proterozoic marine basins were commonly anoxic, either euxinic (sulfidic) or ferruginous (free ferrous iron). To further document redox variations during this interval, a multiproxy geochemical and paleobiological investigation was conducted on the approximately 1000-m-thick Mesoproterozoic (Lower Riphean) Arlan Member of the Kaltasy Formation, central Russia. Iron speciation geochemistry, supported by organic geochemistry, redox-sensitive trace element abundances, and pyrite sulfur isotope values, indicates that basinal calcareous shales of the Arlan Member were deposited beneath an oxygenated water column, and consistent with this interpretation, eukaryotic microfossils are abundant in basinal facies. The Rhenium-Osmium (Re-Os) systematics of the Arlan shales yield depositional ages of 1414±40 and 1427±43 Ma for two horizons near the base of the succession, consistent with previously proposed correlations. The presence of free oxygen in a basinal environment adds an important end member to Proterozoic redox heterogeneity, requiring an explanation in light of previous data from time-equivalent basins. Very low total organic carbon contents in the Arlan Member are perhaps the key--oxic deep waters are more likely (under any level of atmospheric O2) in oligotrophic systems with low export production. Documentation of a full range of redox heterogeneity in subsurface waters and the existence of local redox controls indicate that no single stratigraphic section or basin can adequately capture both the mean redox profile of Proterozoic oceans and its variance at any given point in time.

  14. Mitochondrially targeted fluorescent redox sensors.

    PubMed

    Yang, Kylie; Kolanowski, Jacek L; New, Elizabeth J

    2017-04-06

    The balance of oxidants and antioxidants within the cell is crucial for maintaining health, and regulating physiological processes such as signalling. Consequently, imbalances between oxidants and antioxidants are now understood to lead to oxidative stress, a physiological feature that underlies many diseases. These processes have spurred the field of chemical biology to develop a plethora of sensors, both small-molecule and fluorescent protein-based, for the detection of specific oxidizing species and general redox balances within cells. The mitochondrion, in particular, is the site of many vital redox reactions. There is therefore a need to target redox sensors to this particular organelle. It has been well established that targeting mitochondria can be achieved by the use of a lipophilic cation-targeting group, or by utilizing natural peptidic mitochondrial localization sequences. Here, we review how these two approaches have been used by a number of researchers to develop mitochondrially localized fluorescent redox sensors that are already proving useful in providing insights into the roles of reactive oxygen species in the mitochondria.

  15. Implications of phosphorus redox geochemistry

    NASA Astrophysics Data System (ADS)

    Pasek, Matthew

    2015-04-01

    Phosphorus is the limiting nutrient in many environments. Until recently, redox changes to phosphorus speciation have been confined to the realm of chemical laboratories as phosphorus was considered to be synonymous with phosphate in the natural environment. The few known phosphorus species with a reduced redox state, such as phosphine gas, were considered novelties. Recent work has revealed a surprising role for low redox state organophosphorus compounds -- the phosphonates -- in biogeochemistry. Additionally, phosphite and hypophosphite (the lower oxyanions of phosphorus) have been identified from natural sources, and microbial genomics suggests these compounds may be ubiquitous in nature. Recent work from our laboratory suggests that reduced phosphorus compounds such as phosphite and hypophosphite may be ubiquitous (Pasek et al. 2014). If so, then these species maybe important in the global phosphorus biogeochemical cycle, and could influence global phosphorus sustainability. Additionally, these compounds could have been relevant on the early earth environment, priming the earth with reactive phosphorus for prebiotic chemistry. Reference: Pasek, M. A., Sampson, J. M., & Atlas, Z. (2014). Redox chemistry in the phosphorus biogeochemical cycle. Proceedings of the National Academy of Sciences, 111(43), 15468-15473.

  16. Redox-optimized ROS balance: a unifying hypothesis

    PubMed Central

    Aon, M.A.; Cortassa, S.; O’Rourke, B.

    2010-01-01

    While it is generally accepted that mitochondrial reactive oxygen species (ROS) balance depends on the both rate of single electron reduction of O2 to superoxide (O2.−) by the electron transport chain and the rate of scavenging by intracellular antioxidant pathways, considerable controversy exists regarding the conditions leading to oxidative stress in intact cells versus isolated mitochondria. Here, we postulate that mitochondria have been evolutionarily optimized to maximize energy output while keeping ROS overflow to a minimum by operating in an intermediate redox state. We show that at the extremes of reduction or oxidation of the redox couples involved in electron transport (NADH/NAD+) or ROS scavenging (NADPH/NADP+, GSH/GSSG), respectively, ROS balance is lost. This results in a net overflow of ROS that increases as one moves farther away from the optimal redox potential. At more reduced mitochondrial redox potentials, ROS production exceeds scavenging, while under more oxidizing conditions (e.g., at higher workloads) antioxidant defenses can be compromised and eventually overwhelmed. Experimental support for this hypothesis is provided in both cardiomyocytes and in isolated mitochondria from guinea pig hearts. The model reconciles, within a single framework, observations that isolated mitochondria tend to display increased oxidative stress at high reduction potentials (and high mitochondrial membrane potential, ΔΨm), whereas intact cardiac cells can display oxidative stress either when mitochondria become more uncoupled (i.e., low ΔΨm) or when mitochondria are maximally reduced (as in ischemia or hypoxia). The continuum described by the model has the potential to account for many disparate experimental observations and also provides a rationale for graded physiological ROS signaling at redox potentials near the minimum. PMID:20175987

  17. Redox properties of a constructed wetland: theoretical and practical aspects.

    PubMed

    Síma, Jan; Diáková, Katerina; Pavelcová, Lenka; Havelka, Michal

    2009-03-01

    Constructed wetlands represent a progressive approach to the wastewater treatment. A fundamental prerequisite of the efficient water quality improvement is the presence of redox potential gradients (connected with the aeration of the system) inside the vegetation bed. Redox properties of a constructed wetland were tested in three longitudinal transects crossing the vegetation bed from the inflow zone to the outflow using diverse indicators (e.g., Fe(III)/Fe(II), SO(2-)(4)/S(2-)). Approximately 10-25% of iron was reoxidized in samples taken 10 m from the inflow zone in 2006. Redox processes of iron in artificial (constructed wetland) and natural (peat bog) ecosystems were compared. The peat bog was characterized with higher percentages of Fe(II) (usually ca. 90-100%). Thus, the aeration of the peat land was lower in comparison with the constructed wetland. The constructed wetland efficiently reduced sulfates (average concentrations of 44.7 and 11.2 mg/l at the inflow and the outflow, resp., in 2007). Organics, expressed as COD(Cr) and BOD(5), and NH+(4) were removed with efficiencies of 86.4, 92.2, and 60.4%, respectively. However, total phosphorus (redox processes play a negligible role in this case) was removed only with 39.6% efficiency. Redox properties of the wetland did not significantly depend on the heterogeneity of the treated wastewater flow.

  18. Redox-iodometry: a new potentiometric method.

    PubMed

    Gottardi, Waldemar; Pfleiderer, Jörg

    2005-07-01

    A new iodometric method for quantifying aqueous solutions of iodide-oxidizing and iodine-reducing substances, as well as plain iodine/iodide solutions, is presented. It is based on the redox potential of said solutions after reaction with iodide (or iodine) of known initial concentration. Calibration of the system and calculations of unknown concentrations was performed on the basis of developed algorithms and simple GWBASIC-programs. The method is distinguished by a short analysis time (2-3 min) and a simple instrumentation consisting of pH/mV meter, platinum and reference electrodes. In general the feasible concentration range encompasses 0.1 to 10(-6) mol/L, although it goes down to 10(-8) mol/L (0.001 mg Cl2/L) for oxidants like active chlorine compounds. The calculated imprecision and inaccuracy of the method were found to be 0.4-0.9% and 0.3-0.8%, respectively, resulting in a total error of 0.5-1.2%. Based on the experiments, average imprecisions of 1.0-1.5% at c(Ox)>10(-5) M, 1.5-3% at 10(-5) to 10(-7) M, and 4-7% at <10(-7) M were found. Redox-iodometry is a simple, precise, and time-saving substitute for the more laborious and expensive iodometric titration method, which, like other well-established colorimetric procedures, is clearly outbalanced at low concentrations; this underlines the practical importance of redox-iodometry.

  19. 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.

  20. Hybrid energy storage systems utilizing redox active organic compounds

    SciTech Connect

    Wang, Wei; Xu, Wu; Li, Liyu; Yang, Zhenguo

    2015-09-08

    Redox flow batteries (RFB) have attracted considerable interest due to their ability to store large amounts of power and energy. Non-aqueous energy storage systems that utilize at least some aspects of RFB systems are attractive because they can offer an expansion of the operating potential window, which can improve on the system energy and power densities. One example of such systems has a separator separating first and second electrodes. The first electrode includes a first current collector and volume containing a first active material. The second electrode includes a second current collector and volume containing a second active material. During operation, the first source provides a flow of first active material to the first volume. The first active material includes a redox active organic compound dissolved in a non-aqueous, liquid electrolyte and the second active material includes a redox active metal.

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

    PubMed

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

    2015-01-01

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

  2. Abscisic acid and pyrabactin improve vitamin C contents in raspberries.

    PubMed

    Miret, Javier A; Munné-Bosch, Sergi

    2016-07-15

    Abscisic acid (ABA) is a plant growth regulator with roles in senescence, fruit ripening and environmental stress responses. ABA and pyrabactin (a non-photosensitive ABA agonist) effects on red raspberry (Rubus idaeus L.) fruit development (including ripening) were studied, with a focus on vitamin and antioxidant composition. Application of ABA and/or pyrabactin just after fruit set did not affect the temporal pattern of fruit development and ripening; neither provitamin A (carotenoids) nor vitamin E contents were modified. In contrast, ABA and pyrabactin altered the vitamin C redox state at early stages of fruit development and more than doubled vitamin C contents at the end of fruit ripening. These were partially explained by changes in ascorbate oxidation and recycling. Therefore, ABA and pyrabactin applications may be used to increase vitamin C content of ripe fruits, increasing fruit quality and value. However, treatments containing pyrabactin-combined with ABA or alone-diminished protein content, thus partially limiting its potential applicability.

  3. Effect of sarcoplasmic reticulum Ca2+ content on action potential-induced Ca2+ release in rat skeletal muscle fibres

    PubMed Central

    Posterino, G S; Lamb, G D

    2003-01-01

    This study examined the relationship between the level of Ca2+ loading in the sarcoplasmic reticulum (SR) and the amount of Ca2+ released by an action potential (AP) in fast-twitch skeletal muscle fibres of the rat. Single muscle fibres were mechanically skinned and electric field stimulation was used to induce an AP in the transverse-tubular system and a resulting twitch response. Responses were elicited in the presence of known amounts (0–0.38 mM) of BAPTA, a fast Ca2+ buffer, with the SR Ca2+ pump either functional or blocked by 50 μM 2,5-di-tert-butyl-1,4-hydroquinone (TBQ). When Ca2+ reuptake was blocked, an estimate of the amount of Ca2+ released by an AP could be derived from the size of the force response. In a fibre with the SR loaded with Ca2+ at the endogenous level (≈1.2 mM, expressed as total Ca2+ per litre fibre volume; approximately one-third of maximal loading), a single AP triggered the release of ≈230 μM Ca2+. If a second AP was elicited 10 ms after the first, only a further ≈60 μM Ca2+ was released, the reduction probably being due to Ca2+ inactivation of Ca2+ release. When Ca2+ reuptake was blocked, APs applied 15 s apart elicited similar amounts of Ca2+ release (≈230 μM) on the first two or three occasions and then progressively less Ca2+ was released until the SR was fully depleted after a total of approximately eight APs. When the SR was loaded to near-maximal capacity (≈3–4 mM), each AP (or pair of APs 10 ms apart) still only released approximately the same amount of Ca2+ as that released when the fibre was endogenously loaded. Consistent with this, successive APs (15 s apart) elicited similar amounts of Ca2+ release ≈10–16 times before the amount released declined, and the SR was fully depleted of Ca2+ after a total release calculated to be ≈3–4 mM. When the SR was loaded maximally, increasing the [BAPTA] above 280 μM resulted in an increase in the amount of Ca2+ released per AP, probably because the greater level

  4. 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

  5. [Impulse cytofluorometry of the redox activity of single cells using fluorescent formazan].

    PubMed

    Severin, E; Stellmach, J

    1984-01-01

    The first application of a newly developed fluorescent formazan in flow cytometry is described. The cell surface redox activity of isolated mouse hepatocytes after incubation with the tetrazolium salt forming the new fluorescent formazan and the DNA content after Hoechst staining have been measured simultaneously. 2 parametric distribution patterns have been obtained. This new and sensitive fluorometric technique can be used for automatic measurements of single cells correlating redox activity with other cell parameters.

  6. [Reduction of crude fiber content in safflower meal (Carthamus tinctorius L) and its potential use in human food].

    PubMed

    Martínez Flores, H; Cruz Mondragón, C; Larios Saldaña, A

    1996-12-01

    The purpose of this work was to reduce the content of crude fibre (CF) and to determine the content of phenolics compounds (PC) and trypsin inhibitors (TI) in safflower meal (SM), in order to recommend the possibility of utilization it in human food. The SM (23.3% of CF, 22.4% of protein and 1.75% of PC was grinded in a blender and in a hammer mill respectively, after that, they were classified in particle size by sieving and compared with the SM and their fractions. Grinding in hammer mill was more effective; in this process the yield of the fine fractions was 60.5% and the contents of protein and PC were concentrated by 46.7% and 50%, respectively. The test of TI in SM resulted negative. Grinding and sieving showed to be an easy and cheap mechanical size separation process to reduce CF, which also increase the protein content with a good yield of material. It should be possible the utilization of the fine fractions in human food, provided that the level of incorporation in a food product will be low.

  7. Appraisal of Total Phenol, Flavonoid Contents, and Antioxidant Potential of Folkloric Lannea coromandelica Using In Vitro and In Vivo Assays

    PubMed Central

    Kumar, Tekeshwar; Jain, Vishal

    2015-01-01

    The aim of this study was to determine the impending antioxidant properties of different extracts of crude methanolic extract (CME) of leaves of Lannea coromandelica (L. coromandelica) and its two ethyl acetate (EAF) and aqueous (AqF) subfractions by employing various established in vitro systems and estimation of total phenolic and flavonoid content. The results showed that extract and fractions possessed strong antioxidant activity in vitro and among them, EAF had the strongest antioxidant activity. EAF was confirmed for its highest phenolic content, total flavonoid contents, and total antioxidant capacity. The EAF was found to show remarkable scavenging activity on 2,2-diphenylpicrylhydrazyl (DPPH) (EC50 63.9 ± 0.64 µg/mL), superoxide radical (EC50 8.2 ± 0.12 mg/mL), and Fe2+ chelating activity (EC50 6.2 ± 0.09 mg/mL). Based on our in vitro results, EAF was investigated for in vivo antioxidant assay. Intragastric administration of the EAF can significantly increase levels of superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), and glutathione peroxidase (GSH-Px) levels, and decrease malondialdehyde (MDA) content in the liver and kidney of CCl4-intoxicated rats. These new evidences show that L. coromandelica bared antioxidant activity. PMID:26457224

  8. Keap1 redox-dependent regulation of doxorubicin-induced oxidative stress response in cardiac myoblasts

    SciTech Connect

    Nordgren, Kendra K.S. Wallace, Kendall B.

    2014-01-01

    Doxorubicin (DOX) is a widely prescribed treatment for a broad scope of cancers, but clinical utility is limited by the cumulative, dose-dependent cardiomyopathy that occurs with repeated administration. DOX-induced cardiotoxicity is associated with the production of reactive oxygen species (ROS) and oxidation of lipids, DNA and proteins. A major cellular defense mechanism against such oxidative stress is activation of the Keap1/Nrf2-antioxidant response element (ARE) signaling pathway, which transcriptionally regulates expression of antioxidant genes such as Nqo1 and Gstp1. In the present study, we address the hypothesis that an initial event associated with DOX-induced oxidative stress is activation of the Keap1/Nrf2-dependent expression of antioxidant genes and that this is regulated through drug-induced changes in redox status of the Keap1 protein. Incubation of H9c2 rat cardiac myoblasts with DOX resulted in a time- and dose-dependent decrease in non-protein sulfhydryl groups. Associated with this was a near 2-fold increase in Nrf2 protein content and enhanced transcription of several of the Nrf2-regulated down-stream genes, including Gstp1, Ugt1a1, and Nqo1; the expression of Nfe2l2 (Nrf2) itself was unaltered. Furthermore, both the redox status and the total amount of Keap1 protein were significantly decreased by DOX, with the loss of Keap1 being due to both inhibited gene expression and increased autophagic, but not proteasomal, degradation. These findings identify the Keap1/Nrf2 pathway as a potentially important initial response to acute DOX-induced oxidative injury, with the primary regulatory events being the oxidation and autophagic degradation of the redox sensor Keap1 protein. - Highlights: • DOX caused a ∼2-fold increase in Nrf2 protein content. • DOX enhanced transcription of several Nrf2-regulated down-stream genes. • Redox status and total amount of Keap1 protein were significantly decreased by DOX. • Loss of Keap1 protein was due to

  9. Statins: pleiotropic regulators of cardiovascular redox state.

    PubMed

    Antoniades, Charalambos; Channon, Keith M

    2014-03-10

    Lipid-lowering treatment with statins is one of the most effective therapeutic strategies in cardiovascular medicine because they reduce cardiovascular risk in both primary and secondary prevention. Despite the well-established links between low-density lipoprotein and cardiovascular risk, the clinical benefit from statin treatment is not fully explained by their lipid-lowering potential. A number of pleiotropic effects of statins have been described over the past decade, and their ability to suppress global oxidative stress is probably one of the most important mechanisms by which they exert their beneficial effects on the cardiovascular system. In this Forum, there are review articles discussing the molecular mechanisms by which statins modify redox signaling in the vasculature and the heart. They exert direct effects on the vascular wall and the myocardium or indirect by targeting the interactions between the cardiovascular system and adipose tissue or circulating cell types. The review articles in this Forum follow a translational approach and link the molecular mechanisms by which statins modify cardiovascular redox signaling with their clinical benefit in the prevention and treatment of cardiovascular diseases.

  10. Nitrate bioreduction in redox-variable low permeability sediments

    SciTech Connect

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

    2015-09-09

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

  11. Redox characterization of semiconductors based on electrochemical measurements combined with UV-Vis diffuse reflectance spectroscopy.

    PubMed

    Świętek, Elżbieta; Pilarczyk, Kacper; Derdzińska, Justyna; Szaciłowski, Konrad; Macyk, Wojciech

    2013-09-14

    Several techniques can be applied to characterize redox properties of wide bandgap semiconductors, however some of them are of limited use. In this paper we propose a new modification of the old spectroelectrochemical method developed two decades ago. A procedure based on measurements of the reflectance changes as a function of potential applied to the electrode coated with the studied material appears to be a very convenient tool for characterizing redox properties of semiconductors, forming either transparent or opaque films at a platinum electrode. A discussion on the measured redox parameters of semiconductor films concludes with a definition of a new term, the absorption onset potential of the material.

  12. Atorvastatin ameliorates arsenic-induced hypertension and enhancement of vascular redox signaling in rats

    SciTech Connect

    Sarath, Thengumpallil Sasindran; Waghe, Prashantkumar; Gupta, Priyanka; Choudhury, Soumen; Kannan, Kandasamy; Pillai, Ayyappan Harikrishna; Harikumar, Sankaran Kutty; Mishra, Santosh Kumar; Sarkar, Souvendra Nath

    2014-11-01

    Chronic arsenic exposure has been linked to elevated blood pressure and cardiovascular diseases, while statins reduce the incidence of cardiovascular disease predominantly by their low density lipoprotein-lowering effect. Besides, statins have other beneficial effects, including antioxidant and anti-inflammatory activities. We evaluated whether atorvastatin, a widely used statin, can ameliorate arsenic-induced increase in blood pressure and alteration in lipid profile and also whether the amelioration could relate to altered NO and ROS signaling. Rats were exposed to sodium arsenite (100 ppm) through drinking water for 90 consecutive days. Atorvastatin (10 mg/kg bw, orally) was administered once daily during the last 30 days of arsenic exposure. On the 91st day, blood was collected for lipid profile. Western blot of iNOS and eNOS protein, NO and 3-nitrotyrosine production, Nox-4 and p22Phox mRNA expression, Nox activity, ROS generation, lipid peroxidation and antioxidants were evaluated in thoracic aorta. Arsenic increased systolic, diastolic and mean arterial blood pressure, while it decreased HDL-C and increased LDL-C, total cholesterol and triglycerides in serum. Arsenic down-regulated eNOS and up-regulated iNOS protein expression and increased basal NO and 3-nitrotyrosine level. Arsenic increased aortic Nox-4 and p22Phox mRNA expression, Nox activity, ROS generation and lipid peroxidation. Further, arsenic decreased the activities of superoxide dismutase, catalase, and glutathione peroxidase and depleted aortic GSH content. Atorvastatin regularized blood pressure, improved lipid profile and attenuated arsenic-mediated redox alterations. The results demonstrate that atorvastatin has the potential to ameliorate arsenic-induced hypertension by improving lipid profile, aortic NO signaling and restoring vascular redox homeostasis. - Highlights: • Arsenic increased systolic, diastolic and mean arterial blood pressure and caused dyslipidemia. • Arsenic increased

  13. Design and nutritional properties of potential functional frankfurters based on lipid formulation, added seaweed and low salt content.

    PubMed

    López-López, I; Cofrades, S; Ruiz-Capillas, C; Jiménez-Colmenero, F

    2009-10-01

    The aim of this paper was to design and analyse the nutritional composition (fatty acid profile, cholesterol, mineral and amino acid content) of low-fat frankfurters enriched with n-3 polyunsaturated fatty acids (PUFA) (using algal oil to add 400mg of docosahexanoic acid - DHA/100g of product) as affected by the addition of seaweed (5.5% Himanthalia elongata) and the partial substitution (50%) of animal fat by olive oil (as a source of monounsaturated fatty acids - MUFA) or combinations of olive oil and seaweed. Reduction of NaCl level was also studied. The presence of algal oil produced frankfurters with high long-chain n-3 PUFA contents. The partial substitution of the pork fat by olive oil reduced (P<0.05) saturated fatty acids (SFA) and promoted (P<0.05) MUFA. A healthier lipid formulation (algal and olive oils and the reducing animal fat) produced a good balance of MUFA/SFA, PUFA/SFA and n-6/n-3 ratios. Although adding seaweed had little effect on the lipid and amino acid profiles of frankfurters, it does constitute a means to produce low-sodium products with important dietary fibre content, with better Na/K ratios and rich in Ca.

  14. Acupuncture mechanism and redox equilibrium.

    PubMed

    Zeng, Xiang-Hong; Li, Qian-Qian; Xu, Qian; Li, Fang; Liu, Cun-Zhi

    2014-01-01

    Oxidative stress participates in the pathological process of various diseases. Acupuncture is a component of the health care system in China that can be traced back for at least 3000 years. Recently, increased evidences indicate that acupuncture stimulation could reduce oxidative damage in organisms under pathological state, but the exact mechanism remains unclear. This review focuses on the emerging links between acupuncture and redox modulation in various disorders, such as vascular dementia, Parkinson's disease, and hypertension, ranging from redox system, antioxidant system, anti-inflammatory system, and nervous system to signaling pathway. Although the molecular and cellular pathways studies of acupuncture effect on oxidative stress are preliminary, they represent an important step forward in the research of acupuncture antioxidative effect.

  15. Redox signaling in cardiac myocytes

    PubMed Central

    Santos, Celio X.C.; Anilkumar, Narayana; Zhang, Min; Brewer, Alison C.; Shah, Ajay M.

    2011-01-01

    The heart has complex mechanisms that facilitate the maintenance of an oxygen supply–demand balance necessary for its contractile function in response to physiological fluctuations in workload as well as in response to chronic stresses such as hypoxia, ischemia, and overload. Redox-sensitive signaling pathways are centrally involved in many of these homeostatic and stress-response mechanisms. Here, we review the main redox-regulated pathways that are involved in cardiac myocyte excitation–contraction coupling, differentiation, hypertrophy, and stress responses. We discuss specific sources of endogenously generated reactive oxygen species (e.g., mitochondria and NADPH oxidases of the Nox family), the particular pathways and processes that they affect, the role of modulators such as thioredoxin, and the specific molecular mechanisms that are involved—where this knowledge is available. A better understanding of this complex regulatory system may allow the development of more specific therapeutic strategies for heart diseases. PMID:21236334

  16. Cascade redox flow battery systems

    DOEpatents

    Horne, Craig R.; Kinoshita, Kim; Hickey, Darren B.; Sha, Jay E.; Bose, Deepak

    2014-07-22

    A reduction/oxidation ("redox") flow battery system includes a series of electrochemical cells arranged in a cascade, whereby liquid electrolyte reacts in a first electrochemical cell (or group of cells) before being directed into a second cell (or group of cells) where it reacts before being directed to subsequent cells. The cascade includes 2 to n stages, each stage having one or more electrochemical cells. During a charge reaction, electrolyte entering a first stage will have a lower state-of-charge than electrolyte entering the nth stage. In some embodiments, cell components and/or characteristics may be configured based on a state-of-charge of electrolytes expected at each cascade stage. Such engineered cascades provide redox flow battery systems with higher energy efficiency over a broader range of current density than prior art arrangements.

  17. Redox signaling in acute pancreatitis

    PubMed Central

    Pérez, Salvador; Pereda, Javier; Sabater, Luis; Sastre, Juan

    2015-01-01

    Acute pancreatitis is an inflammatory process of the pancreatic gland that eventually may lead to a severe systemic inflammatory response. A key event in pancreatic damage is the intracellular activation of NF-κB and zymogens, involving also calcium, cathepsins, pH disorders, autophagy, and cell death, particularly necrosis. This review focuses on the new role of redox signaling in acute pancreatitis. Oxidative stress and redox status are involved in the onset of acute pancreatitis and also in the development of the systemic inflammatory response, being glutathione depletion, xanthine oxidase activation, and thiol oxidation in proteins critical features of the disease in the pancreas. On the other hand, the release of extracellular hemoglobin into the circulation from the ascitic fluid in severe necrotizing pancreatitis enhances lipid peroxidation in plasma and the inflammatory infiltrate into the lung and up-regulates the HIF–VEGF pathway, contributing to the systemic inflammatory response. Therefore, redox signaling and oxidative stress contribute to the local and systemic inflammatory response during acute pancreatitis. PMID:25778551

  18. Redox signaling in acute pancreatitis.

    PubMed

    Pérez, Salvador; Pereda, Javier; Sabater, Luis; Sastre, Juan

    2015-08-01

    Acute pancreatitis is an inflammatory process of the pancreatic gland that eventually may lead to a severe systemic inflammatory response. A key event in pancreatic damage is the intracellular activation of NF-κB and zymogens, involving also calcium, cathepsins, pH disorders, autophagy, and cell death, particularly necrosis. This review focuses on the new role of redox signaling in acute pancreatitis. Oxidative stress and redox status are involved in the onset of acute pancreatitis and also in the development of the systemic inflammatory response, being glutathione depletion, xanthine oxidase activation, and thiol oxidation in proteins critical features of the disease in the pancreas. On the other hand, the release of extracellular hemoglobin into the circulation from the ascitic fluid in severe necrotizing pancreatitis enhances lipid peroxidation in plasma and the inflammatory infiltrate into the lung and up-regulates the HIF-VEGF pathway, contributing to the systemic inflammatory response. Therefore, redox signaling and oxidative stress contribute to the local and systemic inflammatory response during acute pancreatitis.

  19. Redox Regulation of Protein Kinases

    PubMed Central

    Truong, Thu H.; Carroll, Kate S.

    2015-01-01

    Protein kinases represent one of the largest families of genes found in eukaryotes. Kinases mediate distinct cellular processes ranging from proliferation, differentiation, survival, and apoptosis. Ligand-mediated activation of receptor kinases can lead to the production of endogenous H2O2 by membrane-bound NADPH oxidases. In turn, H2O2 can be utilized as a secondary messenger in signal transduction pathways. This review presents an overview of the molecular mechanisms involved in redox regulation of protein kinases and its effects on signaling cascades. In the first half, we will focus primarily on receptor tyrosine kinases (RTKs), whereas the latter will concentrate on downstream non-receptor kinases involved in relaying stimulant response. Select examples from the literature are used to highlight the functional role of H2O2 regarding kinase activity, as well as the components involved in H2O2 production and regulation during cellular signaling. In addition, studies demonstrating direct modulation of protein kinases by H2O2 through cysteine oxidation will be emphasized. Identification of these redox-sensitive residues may help uncover signaling mechanisms conserved within kinase subfamilies. In some cases, these residues can even be exploited as targets for the development of new therapeutics. Continued efforts in this field will further basic understanding of kinase redox regulation, and delineate the mechanisms involved in physiologic and pathological H2O2 responses. PMID:23639002

  20. Ceria-based electrospun fibers for renewable fuel production via two-step thermal redox cycles for carbon dioxide splitting.

    PubMed

    Gibbons, William T; Venstrom, Luke J; De Smith, Robert M; Davidson, Jane H; Jackson, Gregory S

    2014-07-21

    Zirconium-doped ceria (Ce(1-x)Zr(x)O2) was synthesized through a controlled electrospinning process as a promising approach to cost-effective, sinter-resistant material structures for high-temperature, solar-driven thermochemical redox cycles. To approximate a two-step redox cycle for solar fuel production, fibrous Ce(1-x)Zr(x)O2 with relatively low levels of Zr-doping (0 < x < 0.1) were cycled in an infrared-imaging furnace with high-temperature (up to 1500 °C) partial reduction and lower-temperature (∼800 °C) reoxidation via CO2 splitting to produce CO. Increases in Zr content improve reducibility and sintering resistance, and, for x≤ 0.05, do not significantly slow reoxidation kinetics for CO production. Cycle stability of the fibrous Ce(1-x)Zr(x)O2 (with x = 0.025) was assessed for a range of conditions by measuring rates of O2 release during reduction and CO production during reoxidation and by assessing post-cycling fiber crystallite sizes and surface areas. Sintering increases with reduction temperature but occurs primarily along the fiber axes. Even after 108 redox cycles with reduction at 1400 °C and oxidation with CO2 at 800 °C, the fibers maintain their structure with surface areas of ∼0.3 m(2) g(-1), higher than those observed in the literature for other ceria-based structures operating at similarly high temperature conditions. Total CO production and peak production rate stabilize above 3.0 mL g(-1) and 13.0 mL min(-1) g(-1), respectively. The results show the potential for electrospun oxides as sinter-resistant material structures with adequate surface area to support rapid CO2 splitting in solar thermochemical redox cycles.

  1. Extracellular Cysteine in Connexins: Role as Redox Sensors

    PubMed Central

    Retamal, Mauricio A.; García, Isaac E.; Pinto, Bernardo I.; Pupo, Amaury; Báez, David; Stehberg, Jimmy; Del Rio, Rodrigo; González, Carlos

    2016-01-01

    Connexin-based channels comprise hemichannels and gap junction channels. The opening of hemichannels allow for the flux of ions and molecules from the extracellular space into the cell and vice versa. Similarly, the opening of gap junction channels permits the diffusional exchange of ions and molecules between the cytoplasm and contacting cells. The controlled opening of hemichannels has been associated with several physiological cellular processes; thereby unregulated hemichannel activity may induce loss of cellular homeostasis and cell death. Hemichannel activity can be regulated through several mechanisms, such as phosphorylation, divalent cations and changes in membrane potential. Additionally, it was recently postulated that redox molecules could modify hemichannels properties in vitro. However, the molecular mechanism by which redox molecules interact with hemichannels is poorly understood. In this work, we discuss the current knowledge on connexin redox regulation and we propose the hypothesis that extracellular cysteines could be important for sensing changes in redox potential. Future studies on this topic will offer new insight into hemichannel function, thereby expanding the understanding of the contribution of hemichannels to disease progression. PMID:26858649

  2. A simple but effective dual redox and fluorescent ion pair receptor based on a ferrocene-imidazopyrene dyad.

    PubMed

    Alfonso, María; Espinosa, Arturo; Tárraga, Alberto; Molina, Pedro

    2011-04-15

    The ferrocene-imidazopyrene dyad, bearing the imidazole ring as the only receptor site, acts as a redox and optical molecular sensor for ion pairs, exhibiting an easily detectable signal change in the redox potential of the ferrocene/ferrocinium redox couple and in the emission spectrum. Perturbation of the emission spectrum follows the order Pb(2+) > Hg(2+) > Zn(2+) for cations and H(2)PO(4)(-) > AcO(-) for anions.

  3. Anr, the anaerobic global regulator, modulates the redox state and oxidative stress resistance in Pseudomonas extremaustralis.

    PubMed

    Tribelli, Paula M; Nikel, Pablo I; Oppezzo, Oscar J; López, Nancy I

    2013-02-01

    The role of Anr in oxidative stress resistance was investigated in Pseudomonas extremaustralis, a polyhydroxybutyrate-producing Antarctic bacterium. The absence of Anr caused increased sensitivity to hydrogen peroxide under low oxygen tension. This phenomenon was associated with a decrease in the redox ratio, higher oxygen consumption and higher reactive oxygen species production. Physiological responses of the mutant to the oxidized state included an increase in NADP(H) content, catalase activity and exopolysaccharide production. The wild-type strain showed a sharp decrease in the reduced thiol pool when exposed to hydrogen peroxide, not observed in the mutant strain. In silico analysis of the genome sequence of P. extremaustralis revealed putative Anr binding sites upstream from genes related to oxidative stress. Genes encoding several chaperones and cold shock proteins, a glutathione synthase, a sulfate transporter and a thiol peroxidase were identified as potential targets for Anr regulation. Our results suggest a novel role for Anr in oxidative stress resistance and in redox balance maintenance under conditions of restricted oxygen supply.

  4. Water-activated graphite felt as a high-performance electrode for vanadium redox flow batteries

    NASA Astrophysics Data System (ADS)

    Kabtamu, Daniel Manaye; Chen, Jian-Yu; Chang, Yu-Chung; Wang, Chen-Hao

    2017-02-01

    A simple, green, novel, time-efficient, and potentially cost-effective water activation method was employed to enhance the electrochemical activity of graphite felt (GF) electrodes for vanadium redox flow batteries (VRFBs). The GF electrode prepared with a water vapor injection time of 5 min at 700 °C exhibits the highest electrochemical activity for the VO2+/VO2+ couple among all the tested electrodes. This is attributed to the small, controlled amount of water vapor that was introduced producing high contents of oxygen-containing functional groups, such as sbnd OH groups, on the surface of the GF fibers, which are known to be electrochemically active sites for vanadium redox reactions. Charge-discharge tests further confirm that only 5 min of GF water activation is required to improve the efficiency of the VRFB cell. The average coulombic efficiency, voltage efficiency, and energy efficiency are 95.06%, 87.42%, and 83.10%, respectively, at a current density of 50 mA cm-2. These voltage and energy efficiencies are determined to be considerably higher than those of VRFB cells assembled using heat-treated GF electrodes without water activation and pristine GF electrodes.

  5. Electrochemical properties of multilayer film assembled by layer-by-layer adsorption of redox polymer

    NASA Astrophysics Data System (ADS)

    Sun, Tao; Zheng, Haitao; Liu, Shiyang; Liu, Pu; Zhou, Jingli; Suye, Shin-ichiro

    2009-07-01

    A redox polymer, poly(ethylenimine)ferrocene (PEI-Fc) was prepared by attaching electroactive ferrocene groups to the backbone of a water soluble, biocompatible polyelectrolyte, poly(ethylenimine), and multilayer film composed of polystyrenesulfonate sodium (PSS) and PEI-Fc was prepared by alternate layer-by-layer (LBL) self-assembly adsorption technique based on the electrostatic force between the opposite charges carried by these two polymers. UV-Vis spectra was used to monitor the LBL process, and the thickness and immobilization amount of each layer were characterized by quartz crystal microbalance (QCM), which showed the formation of nano-scale multilayer structure and linear mass increase dependent on the alternate adsorption cycles. The electrochemical properties of the PEI-Fc/PSS multilayer film modified gold electrode were investigated by cyclic voltammetry. It was observed clearly that the electrochemical properties of this multilayer film were strongly dependent on the layer number and the ferrocene content in PEI-Fc. The electrochemical kinetic was analyzed based on a general model for surface process, and the experimental data fitted well with that evaluated from the above model. This redox polymer showed potential for the construction of reagentless biosensor.

  6. Redox Abnormalities as a Vulnerability Phenotype for Autism and Related Alterations in CNS Development

    DTIC Science & Technology

    2010-10-14

    NOTES 14. ABSTRACT: We hypothesize that low systemic redox potential (GSH/GSSG; cysteine /cystine) reflects a vulnerability phenotype that is...modifications in DNA methylation and histone acetylation /methylation that are reversible with treatment to restore redox potential. In Aim 1 we will...couples GSH/GSSG and cysteine /cystine in blood samples and mouse tissue from Dr. Noble (ongoing; years 1-3). Progress: The preliminary results for

  7. Molecular beam epitaxy of GaNAs alloys with high As content for potential photoanode applications in hydrogen production

    SciTech Connect

    Novikov, S. V.; Staddon, C. R.; Foxon, C. T.; Yu, K. M.; Broesler, R.; Hawkridge, M.; Liliental-Weber, Z.; Walukiewicz, W.; Denlinger, J.; Demchenko, I.

    2009-10-06

    The authors have succeeded in growing GaN1?xAsx alloys over a large composition range (0 < x < 0.8) by plasma-assisted molecular beam epitaxy. The enhanced incorporation of As was achieved by growing the films with high As{sub 2} flux at low (as low as 100 C) growth temperatures, which is much below the normal GaN growth temperature range. Using x-ray and transmission electron microscopy, they found that the GaNAs alloys with high As content x > 0.17 are amorphous. Optical absorption measurements together with x-ray absorption and emission spectroscopy results reveal a continuous gradual decrease in band gap from -3.4 to < 1 eV with increasing As content. The energy gap reaches its minimum of -0.8 eV at x - 0.8. The composition dependence of the band gap of the crystalline GaN{sub 1?x}As{sub x} alloys follows the prediction of the band anticrossing model (BAC). However, our measured band gap of amorphous GaN{sub 1?x}As{sub x} with 0.3 < x < 0.8 are larger than that predicted by BAC. The results seem to indicate that for this composition range the amorphous GaN{sub 1?x}As{sub x} alloys have short-range ordering that resembles random crystalline GaN{sub 1?x}As{sub x} alloys. They have demonstrated the possibility of the growth of amorphous GaN{sub 1?x}As{sub x} layers with variable As content on glass substrates

  8. Albumin-bound fatty acids but not albumin itself alter redox balance in tubular epithelial cells and induce a peroxide-mediated redox-sensitive apoptosis.

    PubMed

    Ruggiero, Christine; Elks, Carrie M; Kruger, Claudia; Cleland, Ellen; Addison, Kaity; Noland, Robert C; Stadler, Krisztian

    2014-04-15

    Albuminuria is associated with metabolic syndrome and diabetes. It correlates with the progression of chronic kidney disease, particularly with tubular atrophy. The fatty acid load on albumin significantly increases in obesity, presenting a proinflammatory environment to the proximal tubules. However, little is known about changes in the redox milieu during fatty acid overload and how redox-sensitive mechanisms mediate cell death. Here, we show that albumin with fatty acid impurities or conjugated with palmitate but not albumin itself compromised mitochondrial and cell viability, membrane potential and respiration. Fatty acid overload led to a redox imbalance which deactivated the antioxidant protein peroxiredoxin 2 and caused a peroxide-mediated apoptosis through the redox-sensitive pJNK/caspase-3 pathway. Transfection of tubular cells with peroxiredoxin 2 was protective and mitigated apoptosis. Mitochondrial fatty acid entry and ceramide synthesis modulators suggested that mitochondrial β oxidation but not ceramide synthesis may modulate lipotoxic effects on tubular cell survival. These results suggest that albumin overloaded with fatty acids but not albumin itself changes the redox environment in the tubules, inducing a peroxide-mediated redox-sensitive apoptosis. Thus, mitigating circulating fatty acid levels may be an important factor in both preserving redox balance and preventing tubular cell damage in proteinuric diseases.

  9. Elevated p66Shc is associated with intracellular redox imbalance in developmentally compromised bovine embryos.

    PubMed

    Bain, Nathan T; Madan, Pavneesh; Betts, Dean H

    2013-01-01

    The in vitro production of mammalian embryos suffers from low efficiency, with 50-70% of all fertilized oocytes failing to develop to the blastocyst stage. This high rate of developmental failure is due, in part, to the effects of oxidative stress generated by reactive oxygen species (ROS). The p66Shc adaptor protein controls oxidative stress response by regulating intracellular ROS levels through multiple pathways, including mitochondrial ROS generation and the repression of antioxidants. This study explored the relationship between p66Shc levels, redox state, and developmental potential in early bovine embryos. Embryo developmental potential was established based on observing their time of first cleavage. P66Shc, catalase, and mitochondrial-specific, manganese-superoxide dismutate (MnSOD) levels were compared between embryos with high and low developmental potentials. Additionally, p66Shc, catalase, and MnSOD content were assayed following a variety of oxidative stress-inducing and-alleviating conditions. Increased developmental potential correlated with significantly lower p66Shc content, significantly higher levels of catalase and MnSOD, and significantly lower intracellular ROS levels (MitoSOX staining) and reduced DNA damage (γ-H2A.X(phospho S139) immunostaining). p66Shc content was increased by either high (20%) O(2) culture or H(2)O(2) treatment, and significantly decreased by supplementing culture media with the antioxidant polyethylene glycol-conjugated catalase. While the abundance of p66Shc varied according to pro/anti-oxidant culture conditions, antioxidant content varied only according to developmental potential. This discrepancy has important implications regarding ongoing efforts towards maximizing in vitro embryo production.

  10. Mycobacterium tuberculosis has diminished capacity to counteract redox stress induced by elevated levels of endogenous superoxide

    PubMed Central

    Tyagi, Priyanka; Dharmaraja, Allimuthu T.; Bhaskar, Ashima; Chakrapani, Harinath; Singh, Amit

    2015-01-01

    Mycobacterium tuberculosis (Mtb) has evolved protective and detoxification mechanisms to maintain cytoplasmic redox balance in response to exogenous oxidative stress encountered inside host phagocytes. In contrast, little is known about the dynamic response of this pathogen to endogenous oxidative stress generated within Mtb. Using a noninvasive and specific biosensor of cytoplasmic redox state of Mtb, we for first time discovered a surprisingly high sensitivity of this pathogen to perturbation in redox homeostasis induced by elevated endogenous reactive oxygen species (ROS). We synthesized a series of hydroquinone-based small molecule ROS generators and found that ATD-3169 permeated mycobacteria to reliably enhance endogenous ROS including superoxide radicals. When Mtb strains including multidrug-resistant (MDR) and extensively drug-resistant (XDR) patient isolates were exposed to this compound, a dose-dependent, long-lasting, and irreversible oxidative shift in intramycobacterial redox potential was detected. Dynamic redox potential measurements revealed that Mtb had diminished capacity to restore cytoplasmic redox balance in comparison with Mycobacterium smegmatis (Msm), a fast growing nonpathogenic mycobacterial species. Accordingly, Mtb strains were extremely susceptible to inhibition by ATD-3169 but not Msm, suggesting a functional linkage between dynamic redox changes and survival. Microarray analysis showed major realignment of pathways involved in redox homeostasis, central metabolism, DNA repair, and cell wall lipid biosynthesis in response to ATD-3169, all consistent with enhanced endogenous ROS contributing to lethality induced by this compound. This work provides empirical evidence that the cytoplasmic redox poise of Mtb is uniquely sensitive to manipulation in steady-state endogenous ROS levels, thus revealing the importance of targeting intramycobacterial redox metabolism for controlling TB infection. PMID:25819161

  11. Spatiotemporal Trends in Oral Cancer Mortality and Potential Risks Associated with Heavy Metal Content in Taiwan Soil

    PubMed Central

    Chiang, Chi-Ting; Lian, Ie-Bin; Su, Che-Chun; Tsai, Kuo-Yang; Lin, Yu-Pin; Chang, Tsun-Kuo

    2010-01-01

    Central and Eastern Taiwan have alarmingly high oral cancer (OC) mortality rates, however, the effect of lifestyle factors such as betel chewing cannot fully explain the observed high-risk. Elevated concentrations of heavy metals in the soil reflect somewhat the levels of exposure to the human body, which may promote cancer development in local residents. This study assesses the space-time distribution of OC mortality in Taiwan, and its association with prime factors leading to soil heavy metal content. The current research obtained OC mortality data from the Atlas of Cancer Mortality in Taiwan, 1972–2001, and derived soil heavy metals content data from a nationwide survey carried out by ROCEPA in 1985. The exploratory data analyses showed that OC mortality rates in both genders had high spatial autocorrelation (Moran’s I = 0.6716 and 0.6318 for males and females). Factor analyses revealed three common factors (CFs) representing the major pattern of soil pollution in Taiwan. The results for Spatial Lag Models (SLM) showed that CF1 (Cr, Cu, Ni, and Zn) was most spatially related to male OC mortality which implicates that some metals in CF1 might play as promoters in OC etiology. PMID:21139868

  12. 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