Electroanalysis may be used in the vanillin biotechnological production.

This study shows that electroanalysis may be used in vanillin biotechnological production. As a matter of fact, vanillin and some molecules implicated in the process like eugenol, ferulic acid, and vanillic acid may be oxidized on electrodes made of different materials (gold, platinum, glassy carbon). By a judicious choice of the electrochemical method and the experimental conditions the current intensity is directly proportional to the molecule concentrations in a range suitable for the biotechnological process.

Reagentless and calibrationless silicate measurement in oceanic waters.

Determination of silicate concentration in seawater without addition of liquid reagents was the key prerequisite for developing an autonomous in situ electrochemical silicate sensor (Lacombe et al., 2007) [11]. The present challenge is to address the issue of calibrationless determination.

Exploration of the global antioxidant capacity of the stratum corneum by cyclic voltammetry.

Cyclic voltammetry is proposed as a new method for evaluating the antioxidant capacity of skin based on the reducing properties of low molecular weight antioxidants (LMWA). Experiments were performed simply by recording the anodic current at 0.9 V/SCE of a platinum microelectrode placed directly on the epidermis surface without any gel or water.

Evaluation of antioxidant properties of dermocosmetic creams by direct electrochemical measurements.

Cyclic voltammetry and linear sweep voltammetry were preliminarily used in order to evaluate the global antioxidant properties of dermocosmetic creams. Experiments were performed by introducing electrodes directly into the creams without any pretreatment of the samples. Current-potential curves showed significant anodic current depending on the antioxidant-containing cream studied.

Biological validation of coenzyme Q redox state by HPLC-EC measurement: relationship between coenzyme Q redox state and coenzyme Q content in rat tissues.

The properties of coenzymes Q (CoQ9 and CoQ10) are closely linked to their redox state (CoQox/total CoQ) x 100. In this work, CoQ redox state was biologically validated by high performance liquid chromatography-electrochemical measurement after modulation of mitochondrial electron flow of cultured cells by molecules increasing (rotenone, carbonyl cyanide chlorophenylhydrazone) or decreasing (antimycin) CoQ oxidation. The tissue specificity of CoQ redox state and content were investigated in control and hypoxic rats.

A bioelectrochemical polypyrrole-containing Fe(CN)6(3-) interface for the design of a NAD-dependent reagentless biosensor.

Ferricyanide ions were immobilized on a platinum electrode surface by means of an electrochemically grown polypyrrole film. The entrapped Fe(CN)6(3-)/Fe(CN)6(4-) redox system displayed a high heterogeneous electron transfer rate. The resulting modified electrode was efficient for the ferricyanide-mediated NADH oxidation catalyzed by a diaphorase.

Indirect electrochemical reduction of methemoglobin: design of the process.

Methemoglobin can be reduced on a platinum cathode using flavin mononucleotide as an oxido-reduction mediator. The process requires the utilization of a filter-press cell with compartments separated by a semi-permeable membrane. Analysis of the various constraints imposed by the process itself and by the nature of the molecules involved shows that the electrolysis cell must operate at a low temperature, in strictly anaerobic conditions, in series with a storage tank, and with fluid circulation rates lower than approximately 0.

Enzymatic amplification for spectrophotometric and electrochemical assays of NAD+ and NADH.

Five different procedures are presented for the enzymatic assay of the sum of NAD+ and NADH concentrations. They are based on the principle of amplification by cycling. The reactions involve oxidation of the formate ion, ethanol, glucose, or carnitine catalyzed by the corresponding dehydrogenases.

Electrochemical reduction of methemoglobin either directly or with flavin mononucleotide as a mediator.

Electrochemical reduction of methemoglobin on a platinum electrode is studied by means of thin layer spectroelectrochemistry. For methemoglobin alone in solution, direct reduction is very slow even for potentials close to those of the reduction of the solvent. The reduction of a methemoglobin-oxyhemoglobin mixture with an imposed potential causes the electrochemical reduction of oxygen, the conversion of oxyhemoglobin into deoxyhemoglobin, and a simultaneous transformation of part of the molecules into methemoglobin.

Electroenzymatic reactors with coenzyme regeneration: A theoretical approach.

A comparison of the relative performance of production techniques using coenzyme or cofactor electrochemical regeneration demonstrates the superiority of those processes in which the enzymatic reaction and the regeneration are conducted in the same reactor as opposed to those in which the reaction and regeneration are separated. For the former type of reactor, a method of calculation is proposed. This method is based on the solution of equations which describe the phenomena in modules representing three areas: the surface of the electrode, a layer where occur simultaneously the transport of material and the enzymatic reaction, and the bulk of the solution.

Spectrophotometric and electrochemical determinations of L(+)-lactate in blood by use of lactate dehydrogenase from yeast.

Lactate can be determined rapidly in blood by spectrophotometric and amperometric (enzyme electrode) procedures based on its oxidation by ferricyanide, the reaction being catalyzed with yeast L(+)-lactate dehydrogenase (cytochrome b2) (EC 1.1.2.