Search results for "Redox"
showing 10 items of 619 documents
Metal-support interaction and redox behavior of Pt(1 wt %)/Ce0.6Zr0.4O2
2006
The catalyst Pt(1 wt %)/Ce(0.6)Zr(0.4)O(2) is studied by CO-temperature programmed reduction (CO-TPR), isothermal oxygen storage complete capacity (OSCC), X-ray absorption spectroscopy (XAS) at the Pt L(III) edge, and in situ X-ray diffraction (in situ XRD), with the aim of elucidating the role of supported metal in CO oxidation by ceria-based three-way catalysts (TWC). The redox behavior of Pt(1 wt %)/Ce(0.6)Zr(0.4)O(2) is compared to that of bare ceria-zirconia. OSCC of redox-aged Pt/ceria-zirconia is twice that of bare ceria-zirconia, and the maximum of CO consumption occurs at a temperature about 300 K lower than redox-aged ceria-zirconia. XAS analysis allows one to evidence the formati…
Modeling hexanal production in oxido-reducing conditions by the yeast Yarrowia lipolytica
2009
International audience; Hexanal produced by cells of a recombinant Yarrowia lipolytica yeast expressing the hydroperoxide lyase (HPL) from green bell pepper fruit was studied under oxido-reducing conditions using the reducing dithiotreitol and oxidizing potassium ferricyanide compounds. The combined effect of pH, linoleic acid 13-hydroperoxides concentration, temperature and oxido-reducing molecules on the hexanal production was studied. Significant positive effects for the hexanal production were found using high concentrations of hydroperoxides (100 mM, 30 g/L). Adding reducing molecules enhanced significantly hexanal production while the oxidizing molecules had an inhibitory effect. Comb…
The formal redox potential of the Yb(III,II) Couple at 0°C in 3.22 molal NaCl medium
2004
Following our previous investigations on aqueous solutions of hypooxidized and iperoxidized species, we managed, by lowering the temperature of the solutions to 0 degrees C, to obtain, by electrochemical methods, Yb(II) and Yb(III) mixtures, enough stable to determine by a potentiometric method the formal redox potential of the Yb(IlI, II) couple. Its value, in a large range of total Ytterbium concentration, is -1233 +/- 3 mV against the molal hydrogen electrode in the 3.22 m NaCl medium.
Effects of redox treatments on the structural composition of a ceria–zirconia oxide for application in the three-way catalysis
2003
Abstract The influence of calcination and redox cycles on the structural modification and redox properties of a ceria–zirconia mixed oxide of nominal composition Ce 0.6 Zr 0.4 O 2 were investigated by XRD and Rietveld refinement, by BET measurement, TPR and OSC analyses. The material is characterized by high total OSC and retains this property after several redox and calcination cycles up to 1273 K, despite the loss of porosity and the decrease of surface area. The Rietveld analysis of the diffractograms allowed to establish that at least two solid solutions are present in the as-prepared sample: a cubic phase, space group Fm-3m, richer in cerium compared to the nominal composition, a tetra…
“Two-Story” Calix[6]arene-Based Zinc and Copper Complexes: Structure, Properties, and O 2 Binding
2017
International audience; A new “two-story” calix[6]arene-based ligand was synthesized, and its coordination chemistry was explored. It presents a tren cap connected to the calixarene small rim through three amido spacers. X-ray diffraction studies of its metal complexes revealed a six-coordinate ZnII complex with all of the carbonyl groups of the amido arms bound and a five-coordinate CuII complex with only one amido arm bound. These dicationic complexes were poorly responsive toward exogenous neutral donors, but the amido arms were readily displaced by small anions or deprotonated with a base to give the corresponding monocationic complexes. Cyclic voltammetry in various solvents showed a r…
Signaux issus du métabolisme mitochondrial : les espèces actives de l'oxygène
2011
Signaux issus du métabolisme mitochondrial : les espèces actives de l'oxygène. Insulino-sécrétion
Selection of probiotic strains and improving the survival and functionality of an academic strain, Bifidobacterium bifidum, by changing the redox pot…
2012
The aim of this work was to select rationally a probiotic strain by setting up a screening method as well as study and understand the impact of the redox potential (Eh) and gas bubbling on the survival of Bifidobacterium bifidum in a fermented dairy product. In a first time, we have developed selection techniques of probiotic bacteria on the criteria of viability / vitality (flow cytometry analysis) and on the criteria of functionality (antioxidant). We were able to select strains of industrial interest as well as an academic strain, Bifidobacterium bifidum.Secondly, we have studied effect of modifying redox potential by gas bubbling on the survival of B. bifidum in a fermented dairy produc…
Contribution to the research of microbial and RedOx bio-indicators for the early characterisation of wood diseases in grapevines
2022
Grapevine trunk diseases, linked to pathogenic fungi whose mechanism of action is still poorly characterised, are responsible for grapevine decline in vineyards throughout the world, causing significant losses in productivity and yield in the wine sector. Given the current lack of effective solutions to stop the establishment of the disease and the development of symptoms, which are irreversible but often late in relation to the pathogenic infection, early diagnosis of these diseases is essential. Considering the grapevine holobiont, i.e. the grapevine and the microbiota interacting with, we hypothesise that early bio-indicators of diseases would make it possible to identify a disturbance i…
Electrochemistry of Bis(pyridine)cobalt (Nitrophenyl)corroles in Nonaqueous Media
2018
International audience; A series of bis(pyridine)cobalt corroles with one or three nitrophenyl groups on the meso positions of the corrole macrocycle were synthesized and characterized as to their electrochemical and spectroscopic properties in dichloromethane, benzonitrile, and pyridine. The potentials for each electrode reaction were measured by cyclic voltammetry and the electron-transfer mechanisms evaluated by analysis of the electrochemical data combined with UV-visible spectra of the neutral, electroreduced, and electroxidized forms of the corroles. The proposed electronic configurations of the initial compounds and the prevailing redox reactions involving the electroactive central c…
Regulation of protein cysteinylation and the inflammatory cascade by thioredoxin-related protein of 14 kDa in pancreas
2020
Although under physiological conditions ROS are essential for normal cell signaling, ROS overproduction under oxidative stress conditions may cause damage to biomolecules. Cysteine residues within proteins are often easily oxidized. Reversible cysteine oxidation is used as a mechanism of redox signaling and control of protein function. However, oxidative stress promotes oxidation of protein thiols, leading to the formation of mixed disulfides between proteins and low-molecular-weight thiols. Disulfide reductases such as thioredoxins can reduce disulfide bonds back to free thiols. Acute pancreatitis is currently one of the leading causes of hospital admission for gastrointestinal disorders, …