Oxido-reductions

Barbier MJ, Beedelievre AM, Beedelievre J (1978) Electrochemical study of tellurium oxido-reduction in aqueous solutions. J Electroanal Chem 94 47-57... 

Relatively far from the present topic and well known, the on-line measurement of the physical and aggregate properties of wastewater does not present any problem. Conductivity, temperature, turbidity and oxido-reduction potential (ORP) are easily measured by well-designed sensors, because these parameters are also used for treatment process control. In practice, turbidity is more used for the treatment of natural water, and ORP for the biological treatment of wastewater. However, conductivity and temperature are often monitored at the same time as the other parameters in this section. 

Metabolism of the major fuels, described above, generates hydrogen atoms or electrons. These are oxidised, not directly, but via a series of oxidations and reductions (oxido-reduction reactions or, alternatively, redox reactions) that... 

Elemental tellurium, treated with strong aqueous alkali, undergoes an oxido-reduction disproportionation giving the corresponding telluride ion which reacts with acetylenes to give divinylic tellurides in modest yields. ... 

Oxido-reduction processes may come into play, for example, by closing or opening a ring when disulfide bridges are present ... 

Conflicting data, due to studies performed on mixtures of compounds in which different oxidation states were present (oxido-reduction processes occur easily, especially in the presence of air657-659) are reported. 

Raney copper is prepared by intensive leaching of a commercial copper-aluminum alloy (50-50 wt%) washed with water until neutral. Bimetallic catalysts are obtained using an oxido-reduction method summarized as n Cu-s + 2 Mn+ -> n Cu2+ + 2 Ms... 

In A, a Raney copper catalyst would be able to hydro-dehydrogenate alcoholic functions (-H, +H) on metallic copper sites. About 10 to 15% of the copper would be hydroxylated copper able to catalyze the degradation reactions DOH, RC, RM. These sites would be more reactive than Cu towards Mn + in the oxido-reduction modification of the initial Raney copper, so that, beeing first exchanged, the rates of DOH, RC, RM decrease. 

As the standard oxido-reduction potential of copper is lower than that of the second metals used in this work we suggest that an electronic transfer from copper to M (Ir, Rh, Ru, Pd, Pt, Au) could generate electrophilic copper M - Cu+ able to catalyze the cyclodehydration according to the scheme ... 

The catalytic properties of copper during polyols conversion in aqueous phase may be drastically modified by some additives. Metals having a standard oxido-reduction potential higher than that of copper (Ir, Rh, Ru, Pd, Pt, Au) can be deposited on it by oxido-reduction reaction. The first atoms of second metal deposited exchange with hydroxylated... 

The second system involves numerous hydrophilic or lipophilic molecules like ascorbic acid (AH-) (vitamin C) and a-tocopherol (aT-OH) (vitamin E). These low-molecular-weight antioxidants (LMWA) reduce ROS by oxido-reduction reactions ... 

Other antioxidant species are synthesized by cells like uric acid, ubiquinol or thiols (cystein, homocystein, etc.). In addition, many compounds found in food display antioxidant properties retinol (vitamin A) and its precursor /(-carotene, and polyphenols (flavonoids, etc.). Figure 8.2 shows the apparent standard potential of some LMWA and ROS explaining the spontaneous oxido-reduction reactions at the origin of the antioxidant protection system. 

Cyclic voltammograms were also performed with platinum microelectrodes on skin surface at regular time intervals of about 7 h. Figure 8.10 shows the typical curve giving the evolution of the anodic current at 0.9V/SCE as a function of time. A sinusoidal evolution was observed for the nine volunteers. Current values as well as the amplitude and the period of the variations were different for each subject. It has been verified that the amplitude of the current variations was significantly higher than the accuracy of the amperometric response. Consequently, the variation of the anodic current was actually due to a variation of the oxido-reductive properties of the skin and was not an artifact of the measurements. 

Cyclic voltammetry proved to be a convenient method to reveal the oxido-reduction properties of the skin and of dermo-cosmetic creams. On the one hand, using microelectrodes, it was for the first time possible to evaluate the antioxidant properties on the skin surface. This simple protocol allowed to study in real time the global oxido-reductive state and to determine several antioxidant species. On the other hand, results showed the effect of oxidative stress on the evolution of the antioxidant properties of dermo-cosmetic products in time. 

Oxidoreductases 916 Oxido-reductive properties e66 Oxygen 105 free radicals 185 gas-sensing electrode 366 reduction 915... 

Variation of oxido-reductive properties of a bulk of cream... 

The variation of the oxido-reduction properties of the cream can be recorded as a function of the time, in different conditions with an atmosphere of air or nitrogen, exposed or protected from light (Fig. 9.6). The reductive properties of the product decrease in each experiment light seems to have the most important influence... 

The literature of metabolism in proteinoids and proteinoid microspheres is reviewed and criticized from a biochemical and experimental point of view. Closely related literature is also reviewed in order to understand the function of proteinoids and proteinoid microspheres. Proteinoids or proteinoid microspheres have many activities. Esterolysis, decarboxylation, animation, deamination, and oxido-reduction are catabolic enzyme activities. The formation of ATP, peptides or oligonucleotides is synthetic enzyme activities. Additional activities are hormonal and inhibitory. Selective formation of peptides is an activity of nucleoproteinoid microspheres these are a model for ribosomes. Mechanisms of peptide and oligonucleotide syntheses from amino acids and nucleotide triphosphate by proteinoid microspheres are tentatively proposed as an integrative consequence of reviewing the literature. 

Selective Oxido-Reductive Processes by Nucleophilic Radical Addition under Mild Conditions... 

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