Cytochrome indirect coulometric titration

Figure 3.42 Indirect coulometric titration of cytochrome c oxidase by incremental generation of MV at Sn02 optically transparent electrode. (A) Spectra recorded during titration. (B) Titration curve, MV added in increments of 0.25 mC. [Adapted from W. R. Heineman, T. Kuwana, and C.R. Hartzell, Biochem. Biophys. Res. Commun. 49 1 (1972).]...

Figure 9. Spectra of cytochrome c (17.5 /tM)-cytochrome c oxidase U2.5 fiM heme a) mixture during reductive indirect coulometric titration using methyl viologen. Titrant increments of 1.04x10" equivalents spectra recorded after each addition of reductive charge. Final two spectra at 605 nm were taken after excess methyl viologen cation radical was present. Adapted from Reference (60) with permission.

Figure 10. Plot of log [cytochrome c (reduced)/cytochrome c(oxidized)Jversus log [cytochrome c oxidase (reduced)/cytochrome c oxidase (oxidized)] for reductive indirect coulometric titration of cytochrome c-cyto-chrome c oxidase mixture. Data points taken from Figure 9 and solid line is computer calculation for the cytochrome c formal potential of 250 mV, the cytochrome c oxidase heme a formal potential of 210 mV, and the cytochrome c oxidase heme formal potential of 350 mV. Adapted from reference (60) with permission.

V. CYTOCHROME C AS MEDIATOR IN INDIRECT COULOMETRIC TITRATIONS OF CYTOCHROME C OXIDASE... 

Figure 7 Difference absorption spectra for an indirect coulometric titration of cytochrome c oxidase. Solution contained 150 xM cytochrome c, 11 pM C5dochrome c oxidase, and less than IpM oxygen. Charge injected in first two reductive increments 5 nmol, 10 nmol thereafter. Optical path length 2.3 mm, solution 0.21 M Tiis, 0.24 M cacodylic acid (0.20 M ionic strength), pH 7.0, 0.5% (v/v) Tween 20.

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