Dichlorophenolindophenol DCIP

Because of the clinical significance of vitamin C, it is essential to In-able to detect and quantify its presence in various biological materials. Ana lytical methods have been developed to determine the amount of ascorbic acid in foods and in biological fluids such as blood and urine. Ascorbic acid may be assayed by titration with iodine, reaction with 2,4-dinitrophenylhy-drazine, or titration with a redox indicator, 2,6-dichlorophenolindophenol (DCIP) in acid solution. The latter method will be used in this experiment because it is reasonably accurate, rapid, and convenient and can be applied to many different types of samples. 

The second method of establishing oxidation states employed redox titration using the redox dye dichlorophenolindophenol (DCIP) based on the knowledge that tetrahydropterins reduce DCIP instantaneously while qui-nonoid dihydropterins react slowly and 7,8-dihydropterins do not reduce DCIP at all. As previously mentioned in this chapter, DCIP oxidation of Moeo within several molybdoenzymes was determined to be a two-electron process, suggesting a dihydropterin reduction state that was speculated to be the quinonoid tautomer. The results of stoichiometric additions of DCIP to the molybdenum complexes of reduced pterins showed that no oxidation of... 

The performance of the pneumatic system, mixing and transfer systems may be tested by using any reaction with a moderately short half time, say 10-20 ms, e.g. the reaction between 2,6-dichlorophenolindophenol, DCIP, and i-ascorbate. Here we illustrate using the reaction between myoglobin and carbon monoxide, but any reaction taking some 50 ms or less to complete may be substituted ... 

Pyruvate dehydrogenase of propionibacteria differs from that of aerobic bacteria in that it does not depend on lipoate and has a similarity with pyruvate cytochrome b oxidoreductase. Castberg and Morris (1978) reported the isolation from cells of P. shermanii of pyruvate oxidase (reducing 2,6-dichlorophenolindophenol (DCIP)) and pyruvate dehydrogenase system (reduces NAD). The pyruvate oxidase could not use NAD as an electron acceptor, and the NAD-dependent enzyme did not transport electrons to DCIP. Unlike the pyruvate oxidase of E. coli, the enzyme from P, shermanii was not activated by phosphatydylcholine in the presence of SDS, and the presence of thiamine diphosphate and Mg " was not required for the activity of purified preparations. 

Table 1 Summary of respiratory chain, complex V and PDHc activity assays. All assays are spectrophotometric assays except for the PDHc assay with CO2 detection, which is a radiochemical assay. The specific inhibitor indicated is used for blank measurements. Non-standard abbreviations UQi nbiquinone-Qi DQ decylubiquinone DCIP 2,6-dichlorophenolindophenol, PK pyruvate kinase LDH lactate dehydrogenase AABS / -[p-(aminophenyl)azo]benzene sulfonic acid ArAt arylamine acetyltransferase...

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