THE CATALYSIS OF ASCORBIC ACID OXIDATION BY COPPER AND ITS COMPLEXES WITH AMINO ACIDS, PEPTIDES, AND PROTEINS
ABSTRACT The oxidation of solutions of ascorbic acid catalyzed by copper and the copper complexes of amino acids, peptides, and proteins has been investigated by manometric and chemical means. The copper-containing solutions were prepared by equilibration with the sparingly soluble salt malachite. The catalytic activity of the complexed copper was found to be dependent upon the type of complexing molecule. For amino acids the more firmly bound copper atoms tended to be the best catalysts. The catalytic activity of the copper complexed to several glycine peptides was approximately one half of the mean value of that of the copper complexed to amino acids. The catalytic activity of copper complexed to bovine plasma albumen and pepsin was lower than that of copper complexed with amino acids or peptides. The more firmly bound copper atoms on pepsin showed a higher catalytic activity than the mean value for all the complexed copper atoms. Sodium chloride markedly reduced the catalytic activity of both free copper and complexed copper. In the absence of sodium chloride free copper was 10 times as effective a catalyst as copper complexed to glycine. In the presence of 0.178 M sodium chloride the complexed copper was twice as effective as free copper.
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ABSTRACT: Treatment of secondary effluents with hydrogen peroxide (10 mg/liter)-ascorbic acid (10 mg/liter)-Cu2+ (0.5 mg/liter) for 60 min resulted in around 99% reduction of the initial plate count. Hydrogen peroxide could be replaced by other peroxygen compounds; ascorbic acid could be replaced by other reducing agents, of which sodium sulfite and ethanol were the most effective. Cu2+, however, could not be replaced by other metal ions without loss of bactericidal efficiency of the ternary combination. Enterobacteriaceae, total and fecal coliforms, staphylococci, and micrococci were reduced by 99.0 to 99.9%. Group D streptococci aerobic spores were reduced by 80 and 15%, respectively. Clostridium perfringens, yeasts, and molds were not killed by the disinfectant combinations. The effect of pH was only minor in the range from 6 to 7.5. At a higher pH value the bactericidal effects tended to decrease. The hydrogen peroxide-ascorbic acid-Cu2+ combination made it possible to obtain 99% reduction within 30 min. When using the hydrogen peroxide-sodium sulfite-Cu2+ or the hydrogen peroxide-ethanol-Cu2+ combinations, 60 min of contact time was necessary to obtain 99% reduction of the initial plate count. Cu2+ combined to an intermediate product of the ascorbic acid autoxidation is the toxic agent, and its penetration into the cell is promoted by hydrogen peroxide.Applied and Environmental Microbiology 10/1982; 44(3):555-60. · 3.68 Impact Factor
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ABSTRACT: Trace amounts of adventitious transition metals in buffer solutions can serve as catalysts for many oxidative processes. To fully understand what role these metals may play it is necessary that buffer solutions be 'catalytic metal free'. We demonstrate here that ascorbate can be used in a quick and easy test to determine if near-neutral buffer solutions are indeed 'catalytic metal free'. In buffers which have been rendered free of catalytic metals we have found that ascorbate is quite stable, even at pH 7. The first-order rate constant for the loss of ascorbate in an air-saturated catalytic metal free solution is less than 6 X 10(-7) s-1 at pH 7.0. This upper limit appears to be set by the inability to completely eliminate catalytic metal contamination of solutions and glassware. We conclude that in the absence of catalytic metals, ascorbate is stable at pH 7.Journal of Biochemical and Biophysical Methods 06/1988; 16(1):27-40. · 2.33 Impact Factor
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ABSTRACT: Neutralized ascorbic acid (AA), buffered or unbuffered and autoclaved or filter-sterilized, was sporicidal for Clostridium. A 0.2% concentration of AA was generally employed, and spore counts were made in a soft-agar modification of Wynne's medium in Prickett tubes. Spores of Clostridium botulinum 115B were less susceptible than those of C. sporogenes PA 3679, whereas C. bifermentans spores were by far the most sensitive. At 75 C, spores of PA 3679 were killed at a rate of about 9% at 0 min (warm-up) to 99+% at 100 min. The lower the temperature, the longer the time needed for a given lethality. The percentage of killing increased with increasing concentrations of AA, and the rate of killing was lower at a higher concentration of spores. At least two mechanisms were operative: a major mechanism involving a product(s) of AA auto-oxidation, and a minor mechanism involving copper-ascorbate toxicity. AA reduced in natural gas was not sporicidal after 18.5 hr at 25 C, whereas 92% of the spores were killed by oxidized AA. Although H(2)O(2) per se was sporicidal, catalase did not reverse lethality of fresh or oxidized AA. Dehydroascorbate was as sporicidal as any AA preparation. Added copper (0.00001%) increased the rate of lethality of freshly prepared AA from 66 to 83% but was not effective with thoroughly oxidized AA. Ethylenediaminetetraacetic acid, NH(4) (+), and phosphate partially reversed AA toxicity, deionized water had no effect, and complex media, as well as thioglycolate, eliminated AA lethality. Since the percentage of killing was affected by spore concentration, AA did not seem to stimulate "lethal germination."Applied microbiology 03/1968; 16(2):349-54.