Oxidation and assay

Table IV. Oxidation and Assay of Selected Phosphorothioate Insecticides...

Analytical Techniques. Sorbic acid and potassium sorbate are assayed titrimetricaHy (51). The quantitative analysis of sorbic acid in food or beverages, which may require solvent extraction or steam distillation (52,53), employs various techniques. The two classical methods are both spectrophotometric (54—56). In the ultraviolet method, the prepared sample is acidified and the sorbic acid is measured at 250 260 nm. In the colorimetric method, the sorbic acid in the prepared sample is oxidized and then reacts with thiobarbituric acid the complex is measured at - 530 nm. Chromatographic techniques are also used for the analysis of sorbic acid. High pressure Hquid chromatography with ultraviolet detection is used to separate and quantify sorbic acid from other ultraviolet-absorbing species (57—59). Sorbic acid in food extracts is deterrnined by gas chromatography with flame ionization detection (60—62). 

The protein was oxidized and reduced as described in Table 3. This table and the assays for binding of L12 to depleted ribosomes, poly(U>directed polyphenylalanine synthesis, and enzymatic acetylation of L12 to form L7 are from Caldwell and coworkers37. 

Drugs can also Interfere with laboratory results by negating certain nonspecific oxidation and reduction reactions essential for the chemical assay. Penicillin, streptomycin and ascorbic acid are known to react with cupric Ion thus, false positive results for glucose may occur If a copper reduction method Is used. If the specific enzymatic glucose-oxidase method Is employed, ascorbic acid can cause a false negative result by preventing the oxidation of a specific chromogen In the reaction. 

SCHWARZ K, BERTELSEN L H, NISSEN L R, GORDNER P T, HEINONEN M I, HOPIA A, HUYNH-BA T, LOMBELET p, MCPHAIL D, SKIBSTED L H and TIJBURG L (2001) Investigation of plant extracts for the protection of processed foods against lipid oxidation. Comparison of antioxidant assays based on radical scavenging, lipid oxidation and analysis of the principal antioxidant components, Eur Food Res Technol, 212, 319-28. 

In oxidation-reduction assays the use of bromine is judiciously carried out as an oxidizing agent effectively for such specific compounds which ultimately results into the formation of both bromine substitution and bromine additive compounds. These products of reaction are produced quantitatively and are mostly water-insoluble in characteristics and more interestingly they take place in an acidic medium. 

Phenothiazines The phenothiazines (PTZs) undergo extensive metabolism. Metabolic routes include S-oxidation, aromatic hydroxylation, N-dealkylation, N-oxidation, and a combination of these processes. Chlorpromazine, for example, possesses 168 possible metabolites, a large proportion of which are pharmacologically active compounds. The development of an HPLC assay capable of resolving a large number of these metabolites is virtually impossible and assays that permit the simultaneous determination of the parent compound and a selected number of active metabolites must suffice. The PTZ group of compounds includes chlorpromazine, thioridazine, fluphenazine, and perphenazine. 

The thiosulfate reductase/rhodanese/APS reductase system is thus supported by evidence from direct enzyme assay, whole-cell metabolism and energetics, and S-labehng experiments and provides a robust hypothesis to explain thionate oxidation and energy conservation in at least some chemolithotrophs. 

Figure 4. Oxidative titration of activated aconitase with potassium fenicyanide. Aliquots of activated aconitase and a measured amount of K3Fe(CN)6 were added to individual EPR tubes, assayed for enzymatic activity ( ), and frozen. After deteimination of the number of spins by EPR at g = 2.01 (x), the samples were thawed and assayed again (o). (Reproduced with permission from Ref. 47. Copyright 1983 American Society Biological Chemists.)...

Two-year animal inhalation studies have shown nickel oxide and nickel subsulfide to be carcinogenic in rats, resulting in alveolar/bron-chiolar adenomas and tumors of the adrenal medulla nickel subsulfide was not carcinogenic to mice, whereas nickel oxide caused equivocal evidence of carcinogenicity in mice based on alveolar/bronchiolar adenomas and carcinomas.Nickel sulfate was not carcinogenic in rodent assays but did cause an inflammatory response in the lungs of animals. 

Figure 1. Oxidation and other reactions of dialiate and triallate indicating mutagenic activities of the products in the S. typhimurium TA 100 assay (revertants/ nanomole without activation/with activation / designates no data available). 2-Chloroacrolein is a dialiate metabolite in the mouse liver microsome-NADPH system. Dichloroallylsulfonic acid is a urinary metabolite of dialiate. The other compounds are potential metabolites of the respective thiocarbamates. The thio-carbamate sulfoxides are unstable at 25°C.

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