Photoinduced oxygen uptake for 9,10-anthraquinone in air-saturated aqueous acetonitrile in the presence of formate, alcohols, ascorbic acid or amines

2006 ◽  
Vol 5 (11) ◽  
pp. 1052-1058 ◽  
Author(s):  
Helmut Görner
Keyword(s):  
Ascorbic Acid ◽  
Oxygen Uptake ◽  
Aqueous Acetonitrile

Oxygen uptake during the mixing of saliva with ascorbic acid under acidic conditions: possibility of its occurrence in the stomach

FEBS Letters ◽  
2003 ◽  
Vol 550 (1-3) ◽  
pp. 64-68 ◽  
Author(s):  
Umeo Takahama ◽  
Sachiko Hirota ◽  
Ayumi Yamamoto ◽  
Takayuki Oniki
Keyword(s):  
Ascorbic Acid ◽  
Oxygen Uptake ◽  
Acidic Conditions

Oxygen uptake and evolution by iron porphyrin enzymes

1959 ◽  
Vol 12 (1) ◽  
pp. 47
Author(s):  
NK King ◽  
ME Winfield
Keyword(s):  
Ascorbic Acid ◽  
Carbon Atom ◽  
Oxygen Uptake ◽  
Cytochrome Oxidase ◽  
Metal Atom ◽  
Iron Porphyrin ◽  
Reduction Step ◽  
The Third ◽  
Catalase Peroxidase ◽  
Electron Deficiency

Three detailed mechanisms are considered for the catalatic decomposition of H2O2. It is shown that the first of these, akin to the earlier hypotheses for catalase action, cannot satisfy the magnetic, titrimetric, and kinetic evidence. The second mechanism involves oxidation of the FeIII porphyrin to the equivalent of FeV. The electron deficiency is distributed over the ligands so that even in the most oxidized complex the iron is in the FeIV or possibly even the FeIII state. In the third scheme it is suggested that the reduction step (in which O2 is liberated) takes place at a carbon atom, while the site of the oxidation is the metal atom as commonly supposed. The liberation of O2 from H2O2 can be catalysed by 6-coordinate ruthenium II complexes. In the catalytic cycle, the metal appears to be oxidized to Rdv, then reduced to RuII. Ethanol or ascorbic acid can substitute for H2O2 in the reduction. Evidence for H2O2 attack on the ligands is suggestive but not conclusive. A brief comment is made on the bonding of oxygen to haemoglobin and myoglobin. The accumulated evidence for the structures of catalase, peroxidase, and myoglobin complexes is utilized in a scheme for the uptake of oxygen by cytochrome oxidase.

scholarly journals ON THE INACTIVATION OF ASCORBIC ACID OXIDASE

1944 ◽  
Vol 27 (3) ◽  
pp. 181-199 ◽  
Author(s):  
Wendell H. Powers ◽  
Charles R. Dawson
Keyword(s):  
Ascorbic Acid ◽  
Oxygen Uptake ◽  
Protective Action ◽  
Dehydroascorbic Acid ◽  
Hydroxylamine Hydrochloride ◽  
Enzymatic Oxidation ◽  
Acid Oxidase ◽  
Experimental Conditions ◽  
Protective Agents ◽  
Ascorbic Acid Oxidase

1. In the absence of protective agents, highly purified ascorbic acid oxidase is rapidly inactivated during the enzymatic oxidation of ascorbic acid under optimum experimental conditions. This inactivation, called reaction inactivation to distinguish it from the loss in enzyme activity that frequently occurs in diluted solutions of the oxidase prior to the reaction, is indicated by incomplete oxidation of the ascorbic acid as measured by oxygen uptake; i.e., "inactivation totals." 2. A minor portion of the reaction inactivation appears to be due to environmental factors such as rate of shaking of the manometers, pH of the system, substrate concentration, and oxidase concentration. The presence of inert protein (gelatin) in the system ameliorates the environmental inactivation to a considerable extent, and variation of the above factors in the presence of gelatin has much less effect on the inactivation totals than in the absence of gelatin. 3. A major portion of the reaction inactivation of the oxidase appears to be due to some factor inherent in the ascorbic acid-ascorbic acid oxidase-oxygen system, possibly a highly reactive "redox" form of oxygen other than H2O2 or H2O. The inactivation cannot be attributed to dehydroascorbic acid, the oxidation product of ascorbic acid. 4. Small amounts of native catalase, native peroxidase, native or denatured methemoglobin, and hemin when added to the system, markedly protect the oxidase against inactivation. Cytochrome c has no such protective action. Likewise proteins such as egg albumin, gelatin, denatured catalase, or denatured peroxidase show no such protective action. 5. None of the protective agents mentioned above affect the initial rate of oxygen uptake or change the total oxygen absorbed for complete oxidation of the ascorbic acid, and hence do not act by removal of hydrogen peroxide, per se. 6. Sodium azide and hydroxylamine hydrochloride which inhibit catalase and peroxidase activity also inhibit the protective action of these iron-porphyrin enzymes.

Enzymic diagnosis of copper deficiency in subterranean clover. II. A simple field test

1982 ◽  
Vol 33 (6) ◽  
pp. 981 ◽  
Author(s):  
E Delhaize ◽  
JF Loneragan ◽  
J Webb
Keyword(s):  
Ascorbic Acid ◽  
Oxygen Uptake ◽  
Field Test ◽  
Oxidase Activity ◽  
Room Temperature ◽  
Copper Deficiency ◽  
Subterranean Clover ◽  
Ascorbate Oxidase ◽  
Copper Status ◽  
Dark Blue

A rapid, simple and robust field test is described for diagnosing copper deficiency in subterranean clover plants by measuring ascorbate oxidase activity in young folded leaf blades (YFL) homogenized in phosphate buffer. The test measures activity by counting the drops of iodine required to titrate, to a dark blue end-point, excess ascorbic acid added to and incubated for 20 min with a YFL homogenate. When reagent control titrations had titres of 11 drops of iodine, YFL homogenates from copper-adequate plants had titres of 2-3 drops, from copper-deficient plants 6-11, and from plants with marginal copper supply 4-5 drops. The test was standardized against the measurement of ascorbate oxidase activity in YFL by oxygen uptake. Ascorbate oxidase activity was remarkably insensitive to assay temperature, decreasing by only one-third with decreasing temperature from 30 to 10�C. It was also very stable in both homogenates and whole leaves. At room temperature, activity dropped by only 25% in homogenates after 6 h and in whole leaf blades after 48 h. When stored in ice, leaf blades retained full activity for at least 5 days. Diagnosis of copper deficiency by the new test agreed closely with diagnosis based on copper analysis of young open leaves taken from the same subterranean clover plants in field pastures. The test should allow extension workers to give on-the-spot advice about the copper status of pastures containing subterranean clover.

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