Magnetic Studies on the Ferri‐haem Undecapeptide of Cytochrome c

Abstract

The pH‐dependence of the magnetic moment of a ferri‐haem undecapeptide, produced by peptic digestion of cytochrome c, has been measured in aqueous solution using a nuclear magnetic resonance method. Below pH 3 the magnetic moment is consistent with the presence of hydroxo‐bridged dimers of high‐spin iron(III). Above pH 7 the iron(III) is low‐spin, the spin crossover conforming to a simple titration curve with pK 6.3 (n= 1). This transition is discussed with reference to spectrophotometric studies of ligand binding at the haem. Copyright © 1976, Wiley Blackwell. All rights reserved