The oxidation of ascorbic acid and its reduction in vitro and in vivo

The outstanding chemical property of ascorbic acid (vitamin C) is that it is a reducing agent. The suggestion is obvious that its physiological function may be associated with this property, and, if it is oxidized reversibly, with its behavior in an oxidation-reduction system. It is desirable therefore to know the oxidation-reduction potential of ascorbic acid

The oxidation-reduction potential of coenzyme I

The oxidation-reduction potential of cozymase (diphosphopyridine nucleotide) was calculated from the free energies of formation of aqueous d-alanine and d-glutamic acid based on thermal data, and the equilibria measured by Wurmser and Filitti-Wurmser(1) for pyruvate + 2H+ + 2(e) ⇌ alanine + H2O, by Cohen(2) for α-ketoglutarate + alanine ⇌ d-glutamate and pyruvate, and by von Euler et al.(3) for the reaction α-ketoglutarate + NH+4 + reduced cozymase ⇌ glutamate + oxidized cozymase. The value for the potential so calculated is at 30° E’0 = -0.072 - 0.03 pH ± 0.0008 volt

Coupled oxidation–reduction of butanol–hexanal by resting Rhodococcus erythropolis NCIMB 13064 cells in liquid and gas phases

Rhodococcus erythropolis is a promising Gram-positive bacterium capable of numerous bioconversions including those involving alcohol dehydrogenases (ADHs). In this work, we compared and optimized the redox biocatalytic performances of 1-butanol-grown R. erythropolis NCIMB 13064 cells in aqueous and in non-conventional gas phase using the 1-butanol–hexanal oxidation–reduction as model reaction. Oxidation of 1-butanol to butanal is tightly coupled to the reduction of hexanal to 1-hexanol at the level of a nicotinoprotein–ADH-like enzyme. Cell viability is dispensable for reaction. In aqueous batch conditions, fresh and lyophilized cells are efficient redox catalysts (oxidation–reduction rate = 76 micromol min−1 g cell dry mass−1) being also reactive towards benzyl alcohol, (S)-2-pentanol, and geraniol as reductants. However, butanol hexanal oxidation–reduction is strongly limited by product accumulation and by hexanal toxicity that is amajor factor influencing cell behavior and performance. Reaction rate is maximal at 40 ◦C pH 7.0 in aqueous phase and at 60 ◦C- pH 7.0–9.0 in gas phase. Importantly, lyophilized cells also showed to be promising redox catalysts in the gas phase (at least 65 micromol min−1 g cell dry mass−1). The system is notably stable for several days at moderate thermodynamic activities of hexanal (0.06–0.12), 1-butanol (0.12) and water (0.7)

Study of actinide chemistry in saturated potassium fluoride solution

Study concerning the chemistry of actinides in saturated KF solution included work with neptunium, uranium, and americium. Solubilities, absorption spectra, oxidation-reduction reactions, and solid compounds which can be produced in KF solution were examined. The information is used for preparation of various materials from salts of the actinides

Some of the oxidation-reduction properties of the chorionic gonadotropic hormone

Gurin, Bachman, and Wilson (1-3) have recently made important contributions to our knowledge of the chemical nature of the gonadotropic hormone of pregnancy urine. They have given a method for the preparation of the hormone in a highly purified form and have described many of its outstanding chemical and physical properties. We have been especially interested in the reference of these authors to the unexplained, continuous, and apparently spontaneous inactivation of their highly purified material which takes place, particularly in aqueous solution, without, detectable loss or rupture of certain portions of the molecule (3). Earlier communications (4-6) have called attention to our observations relative to the oxidation and inactivation of a reducing factor of pregnancy urine which appears to be the chorionic gonadotropic hormone. Some of our more recent findings appear to shed light upon the observations of the above authors. The spontaneous oxidation of this reducing factor proceeds at a very slow rate but is more rapid in aqueous solution than in urine, where other stronger reducing agents tend to protect it. If activating agents are added and moderate heat is applied, the activity becomes of sufficient magnitude to bring about the reduction of dilute solutions of iodine or other oxidants. The object of this paper is to describe some of the rather unusual characteristics of this oxidation-reduction system

The role of the enzyme in the succinate-enzyme-fumarate equilibrium

The following is an account of an investigation into the role of the enzyme in the succinate-enzyme-fumarate equilibrium. The method consisted in the comparison of the value of the free energy change in this reaction obtained from oxidation-reduction potentials, with that calculated from the entropies and other physicochemical properties of succinic acid and fumaric acid

Determination of carbon by the oxidation reduction reaction with chromium

Free carbon was determined in silicon and boron carbides in ash, oxides, and other materials by oxidation to carbon dioxide with a mixture of K2Cr2O7 + H2SO4. The determination was made from the amount of CR(6) consumed, by adding excess Mohr's salt and titrating with a standard solution of KMnO4. The amount of Cr(6) self reduced was determined in a blank test. Optimum oxidation and conditions were achieved when the volumes of 5% k2Cr2Oz and H2SO4 were equal. The mixture was boiled for 1-2 hours using a reflex condenser. The volume should not be reduced, in order to avoid an increase in the sulfuric acid concentration. The relative error was 4-7% for 0.005-0.04 g C and less than or equal to 3.5% for 0.1 g C

Anion exchange membranes for electrochemical oxidation-reduction energy storage system

Oxidation-reduction couples in concentrated solutions separated by appropriate ion selective membranes were considered as an attractive approach to bulk electrical energy storage. A key problem is the development of the membrane. Several promising types of anionic membranes are discussed which were developed and evaluated for redox energy storage systems. The copolymers of ethyleneglycoldimethacrylate with either 2-vinylpyridine or vinylbenzl chloride gave stable resistance values compared to the copolymer of vinylbenzlchloride and divinylbenzene which served as the baseline membrane. A polyvinylchloride film aminated with tetraethylenepentamine had a low resistance but a high ion transfer rate. A slurry coated vinylpyridine had the lowest ion transfer rate. All these membranes functioned well in laboratory cells at ambient temperatures with the acidic chloride oxidant/reductant system, Fe 3, Fe 2/Ti 3, Ti 4