MEASUREMENT OF OXIDATION–REDUCTION CONDITIONS IN WHEAT LEAF SAP BY A POTENTIOMETRIC METHOD

1960 ◽  
Vol 38 (3) ◽  
pp. 387-398 ◽  
Author(s):  
Rudolf Kaul ◽  
Michael Shaw
Keyword(s):  
Methylene Blue ◽  
Redox System ◽  
Platinum Electrodes ◽  
Anaerobic Conditions ◽  
Mature Leaves ◽  
Reduction Potentials ◽  
Oxidation Reduction ◽  
Wheat Leaf ◽  
Steady Level ◽  
New System

Extracts from primary leaves of Little Club wheat, prepared under anaerobic conditions, gave oxidation–reduction potentials in the range of −180 mv to −140 mv at pH 6 when measured potentiometrically with prepolarized platinum electrodes. These poorly poised potentials are believed to represent a flavin system. By mixing mediators (e.g. methylene blue and riboflavin) with the extracts stable average potentials were achieved. These ranged from −70 to +70 mv. Coleoptiles and very young primary leaves exhibited relatively low average potentials, which climbed to a steady level in 8 to 10 days after sowing. This change was accompanied by a quantitative shift between three poising systems found in the leaves by redox titrations. The results suggested that ascorbic acid becomes the dominating redox system in extracts from mature leaves. At senescence, indicated by yellowing, a new system dominates the redox background. This exhibited quinonic properties.

scholarly journals Anaerobic and aerobic beer aging

2010 ◽  
Vol 28 (No. 1) ◽  
pp. 18-26 ◽  
Author(s):  
J. Šavel ◽  
P. Košín ◽  
A. Brož
Keyword(s):  
Methylene Blue ◽  
Methyl Red ◽  
Air Oxidation ◽  
Anaerobic Conditions ◽  
Redox Indicators ◽  
Oxidation Reduction ◽  
Reversible Redox ◽  
Yellow Orange ◽  
Oxidoreductase Enzymes ◽  
Transient Metals

Yellow, orange, red and brown pigments are formed by air oxidation of single polyphenols or by thermal degradation of sugars to caramels. Caramels increase their colours during anaerobic heating or decrease them by air oxidation. Epicatechin and caramel undergo reversible redox reaction followed by degradation and/or polymerisation at beer aging. That is why both of these colour compounds, besides acting as acid/alkali indicators, can also represent redox indicators that gradually become irreversible. These reactions are accelerated by transient metals or buffering solutions and are therefore more distinct in tap or brewing water than in deionised water. The kind of the brewing water then predetermines not only the beer attributes but also the course of beer aging. Coloured pigments can be partially bleached by reducting agents such as yeast oxidoreductase enzymes and the colour can be then recovered by oxidation; this depends on their polymerisation degree. Methylene blue and methyl red can be used as artificial oxidation-reduction indicators for the study of the redox potential changes because they act reversibly or irreversibly under aerobic or anaerobic conditions, respectively.

THE PHYSIOLOGY OF HOST–PARASITE RELATIONS: VI. OXIDATION–REDUCTION CHANGES IN WHEAT LEAF SAP CAUSED BY RUST INFECTION

1960 ◽  
Vol 38 (3) ◽  
pp. 399-407 ◽  
Author(s):  
Rudolf Kaul ◽  
Michael Shaw
Keyword(s):  
Short Circuit ◽  
Redox Mediators ◽  
Rust Infection ◽  
Reduction Potentials ◽  
Oxidation Reduction ◽  
Oxidation Reduction Potential ◽  
Wheat Leaf ◽  
Host Parasite ◽  
Different Levels ◽  
Reduced State

Extracts of healthy and rusted leaves of Little Club and Khapli wheats were made under anaerobic conditions. Oxidation–reduction potentials in the extracts were measured at two different levels both in the presence and in the absence of both methylene blue and riboflavin as redox mediators. At the lower level (i.e. in the absence of mediators) a reversible rise in potential was noted during the course of rust infection on Little Club; with Khapli the rise was similar but was not reversed. The response to rust infection of resistant and susceptible plants was also reflected in characteristic changes in the average potentials at higher levels (i.e. in the presence of mediators). After infection the oxidation–reduction balance of susceptible tissue was reorganized by the introduction of new systems which were found in the reduced state only. After infection the oxidation–reduction potential of resistant tissue was only poorly poised as indicated by a rise in the average potentials and as demonstrated by oxidation– reduction titrations.The results are discussed and the possibility is considered that a rust-induced catalyst may “short circuit” the chain of hydrogen transport, thus initiating all the observed redox changes.

scholarly journals THE RELATION OF THE BACTERIOSTATIC ACTION OF CERTAIN DYES TO OXIDATION-REDUCTION PROCESSES

1929 ◽  
Vol 49 (4) ◽  
pp. 575-592 ◽  
Author(s):  
René Dubos
Keyword(s):  
Methylene Blue ◽  
Malachite Green ◽  
Oxidation Potential ◽  
Reduced Form ◽  
Reduction Processes ◽  
Reduction Potentials ◽  
Bacteriostatic Action ◽  
Oxidation Reduction

Oxidized indophenols and methylene blue are bacteriostatic for Pneumococcus and hemolytic streptococci of human and bovine origin, while the indigoes, malachite green and litmus are not toxic. 2-Chloroindophenol, the most positive of the indicators of oxidation-reduction potentials used, is also the only one to have a bacteriostatic action on cheese strains of Streptococcus hæmolyticus. Methylene blue and the indophenols are no longer bacteriostatic when present in a reduced form in a medium capable of maintaining them in such a condition. A comparison of these results with the growth in plain broth of the organisms studied suggests that the "inhibiting" dyes "poise" the medium at an oxidation potential outside the range in which the inhibited organisms can grow.

125. Technique for obtaining Anaerobic Milk, with some Observations on its CO2 Content

1936 ◽  
Vol 7 (1) ◽  
pp. 25-28 ◽  
Author(s):  
Christopher James Jackson
Keyword(s):  
Blood Plasma ◽  
Gas Analysis ◽  
Anaerobic Conditions ◽  
Reduction Potentials ◽  
Oxidation Reduction

1. A method has been described for obtaining milk anaerobically from the udder.2. A technique for transferring anaerobically drawn milk to an electrode vessel for the determination of oxidation-reduction potentials under anaerobic conditions has been described.3. A technique for transferring anaerobically drawn milk to a van Slyke apparatus for gas analysis has been described.4. The total CO2 of cows’ milk is about half that of their blood plasma.

Factors in the Reduction of Methylene Blue in Milk

1936 ◽  
Vol 7 (1) ◽  
pp. 31-40 ◽  
Author(s):  
Christopher James Jackson
Keyword(s):  
Methylene Blue ◽  
Reduction Potential ◽  
Visible Spectrum ◽  
Redox System ◽  
Commercial Application ◽  
Low Concentration ◽  
Oxidation Reduction ◽  
Oxidation Reduction Potential

1. Bacteria may play but an insignificant part in the reduction of methylene blue in milk, though their de-oxygenating effect may be of influence in the commercial application of the test.2. Milk as it exists in the udder, or milk drawn anaerobically, reducesmethylene blue almost instantaneously, whereas the same milk exposed to oxygen will usually take more than 10 hours to reduce.3. The oxidation-reduction potential of anaerobically drawn milk is much lower than the same milk exposed to oxygen, and in accordance with its behaviour toward methylene blue.4. Evidence is given for the presence of a redox system, present in low concentration, as responsible for the reduction of methylene blue.5. Although the addition of small amounts of cysteine or glutathione to milk leads to the reduction of methylene blue, their absence from milk excludes them as possible factors in the normal reduction.6. The possibility that lactoflavin may furnish the redox system is suggested.7. The reduction of methylene blue in milk is catalysed by light in the visible spectrum.

scholarly journals The oxidation-reduction potentials of cytochrome o + c4 and cytochrome o purified from Azotobacter vinelandii

1979 ◽  
Vol 181 (3) ◽  
pp. 763-766 ◽  
Author(s):  
T Yang ◽  
D O'Keefe ◽  
B Chance
Keyword(s):  
Azotobacter Vinelandii ◽  
Anaerobic Conditions ◽  
Midpoint Potential ◽  
Reduction Potentials ◽  
Cytochrome O ◽  
Oxidation Reduction ◽  
Ph Range

Oxidation-reduction titrations of Azotobacter vinelandii cytochrome o + c4 and cytochrome o were performed with simultaneous potential and absorbance measurements under anaerobic conditions. Cytochrome c4 has a midpoint potential (Em, 7.4) of 260mV and purified cytochrome o has an Em, 7.4 of −18mV. Little change in the midpoint potential of cytochrome o was observed when titrated in the pH range 6.2–9.8.

scholarly journals THE ROÔLE OF CARBOHYDRATES IN BIOLOGICAL OXIDATIONS AND REDUCTIONS. EXPERIMENTS WITH PNEUMOCOCCUS

1929 ◽  
Vol 50 (2) ◽  
pp. 143-160 ◽  
Author(s):  
René Dubos
Keyword(s):  
Methylene Blue ◽  
Bacterial Culture ◽  
Reducing Power ◽  
Side Reactions ◽  
Thiol Compounds ◽  
Reduction Potentials ◽  
Oxidation Reduction ◽  
Glucose System ◽  
Synthetic Media ◽  
Reduction Scale

The reducing power of plain broth cultures of Pneumococcus is largely dependent upon the presence in the medium at the time when the reduction test is performed of certain metabolites. The washed cells of Pneumococcus are able to reduce the various indicators of oxidation-reduction potentials in the presence of glucose. The relative velocity of reduction of these indicators is determined by the number of cells used in the test, the concentration of the dyes, and their position in the oxidation reduction scale. Oxidized thiol compounds (glutathione, cystine, oxidized thioglycollic acid) are likewise rapidly reduced by glucose in the presence of washed cells of Pneumococcus. This Pneumococcus-glucose system is able to form peroxide under aerobic conditions. Those substances which form peroxide in the presence of Pneumococcus cells are also the ones which Cole found to be active in changing hemoglobin into methemoglobin under the same conditions. The power of washed cells of Pneumococcus to reduce methylene blue in the presence of glucose is dependent on at least 2 constituents: one which can be readily removed from the cell by washing. Sugar-free meat infusion will function instead of it. The other is inactivated more slowly by the process of washing and is destroyed by 10 minutes heating at 55°C. The interreaction between the glucose and the cell seems to result in a fundamental reaction in which one molecule of glucose becomes able to reduce rapidly one molecule of methylene blue. The existence of side-reactions often obscures this ratio. The significance of these observations is considered in relation to the nature and mechanism of the "activation" of metabolites, the preparation of synthetic media, the phenomena of growth, and the meaning of the expression "reducing power of a bacterial culture."

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