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At least 109 records · Page 6Linked to original sources
PubMed1990

Nonenzymatic NADPH-dependent reduction of 2,6-dichlorophenol-indophenol.

The reduction of 2,6-dichloroindophenol (DCIP) by direct interaction with NADPH was studied. The results indicate that reduction proceeds via a direct electron transfer from NADPH to DCIP, with no oxygen consumption, and a rate constant of k = 4.69 M-1.s-1. The reduced DCIP can rapidly transfer its electrons to potassium ferricyanide (K3Fe(CN)6) or ferricytochrome c, but not to nitro blue tetrazolium. Superoxide dismutase inhibits DCIP reduction in an oxygen-dependent manner by favoring the reoxidation of the reduced DCIP. We therefore conclude DCIP is not suitable for detecting O2- when the nucleotides NADH or NADPH are present.

2,6-Dichloroindophenol↗
PubMed1992

Correction for creatine interference with the direct indophenol measurement of NH3 in steady-state nitrogenase assays.

Creatine was identified as a major source of interference with the direct phenol/hypochlorite colorimetric determination of ammonia in nitrogenase reaction mixtures. A method is described for removing other compounds which inhibit color development and for compensating for the interference produced by creatine. This method avoids time-consuming microdiffusion and also routinely makes available the efficiency of ATP hydrolysis coupled to substrate reduction (ATP/2e ratio) with N2 as a reducible substrate. Using this method we determined values for this ratio at 30 degrees C of 4.87 +/- 0.03 during the reduction of protons to H2 and 7.16 +/- 0.14 during the reduction of N2 by the vanadium-containing nitrogenase of Azotobacter chroococcum.

Adenosine Triphosphate↗
PubMed1976

Photometric determination of nitrogen. Wet incineration followed by formation of indophenol blue with salicylate/hypochlorite.

Ammonia in wet incineration residues has been analyzed photometrically by a modified Berthelot reaction using a water-free digestion mixture. Phenol is substituted by salicylate in the dye-producing reaction. The method can be adapted for any biological material with a minimum content of 0.04 mug N/sample. Nonprotein nitrogen may be determined in the supernatant of TCA precipitates.

Humans↗
PubMed1967

Carbon dioxide and the reduction of indophenol and ferricyanide by chloroplasts.

Pea chloroplasts isolated in salt media show decreased rates of 2:6 dichlorophenolindophenol (DCPIP) and ferricyanide reduction when depleted of CO(2) at pH values below 7.5. The greatest effect of CO(2) was on uncoupled systems. The incorporation of 10(-2), 2 x 10(-2) and 4 x 10(-2)m sodium acetate into the reaction mixtures progressively increased the bicarbonate concentration required for half maximal rates of reduction of DCPIP. The reaction was saturated by bicarbonate concentrations of 1 to 4 x 10(-2)m. With both DCPIP and ferricyanide, the addition of bicarbonate to illuminated chloroplast systems depleted of CO(2) gave very rapid increases in the rates of reduction. Bicarbonate also stimulated oxygen uptake by the illuminated chloroplasts when added hydrogen acceptors had been reduced. There was no effect of bicarbonate on ferricyanide reduction at low light intensities, but with DCPIP reduction, the apparent magnitude of the effect was independent of light intensity. This suggests that DCPIP reacts with the chloroplast electron transport chain at a site nearer to a photochemical stage than does ferricyanide. It also suggests that CO(2) has at least 2 sites of action.

Journal Article↗