Elsevier

Methods in Enzymology

Volume 54, 1978, Pages 411-435
Methods in Enzymology

[23] Redox potentiometry: Determination of midpoint potentials of oxidation-reduction components of biological electron-transfer systems

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This chapter discusses the determination of midpoint potentials of oxidation–reduction components of biological electron-transfer systems using redox potentiometry. The experimental goal is to measure the redox potential, Eh, and a corresponding state of oxidation or reduction of a redox couple: Eh is measured by electrodes, while the state of oxidation-reduction of a redox component is measured by some physical technique, usually some form of spectrometry. The character of the biological redox component usually dictates the chosen technique; the character also will dictate whether the oxidized or reduced form is measured. Several such correlations of Eh and state of oxidation or reduction should be taken at Eh values that extend over the range that encompasses the central part of the expected Nernst curve. To make the analysis straightforward it is preferable to obtain readings for the state of oxidation-reduction as nearly fully oxidized and reduced as possible. The information in the chapter describes the Nernst curve of the redox couple and provides the standard half reduction or midpoint potential value and the number of electrons.

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