ELECTROMERIC ANALYSIS OF CYTOCHROMES IN MITOCHONDRIA

Potentiometric techniques have been used to examine the interactions of certain redox dyes with mitochondria. Most of the dyes tested proved unsuitable in low concentrations for analysis by potentiometry, and, at high concentrations, they either had untoward effects on the mitochondria or served themselves as electron transfer reagents. However, tetramethyl p-phenylenediamine proved an exception in that it gave a rapid response at the platinum electrode at 10 μm concentration and equilibrated rapidly with a component in the electron transfer system. Since this reagent was used in catalytic concentrations, it did not serve as a donor or sink of electrons, but rather as an indicator of the redox potential of a component of the mitochondria during respiration. Analysis of potential changes on adding ADP, inhibitors, or uncouplers, and comparison with spectroscopic data, enabled a correlation of the potential of TMPD with the response of cytochrome c. Polarographic analysis facilitated the examination of redox reagents which did not react rapidly in potentiometric analysis. The specificity of the reagent toward particular components of the mitochondrial chain depended on the reagent used. Vitamin K5 proved to have a preferential specificity toward cytochrome b as shown by its polarographic response to the addition of reagents that alter the electron transfer characteristics of the mitochondria. © 1968.