Magnetic studies on the ferri-haem undecapeptide of cytochrome c.
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.
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D003574:Cytochrome c Group / Q000032:analysis*; D006418:Heme / Q000031:analogs & derivatives*; D006427:Hemin / Q000032:analysis*; D006736:Horses; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000032:analysis; D007525:Isoelectric Focusing; D009682:Magnetic Resonance Spectroscopy; D009842:Oligopeptides / Q000032:analysis*
D000596:Amino Acids; D003574:Cytochrome c Group; D009842:Oligopeptides; D006418:Heme; D006427:Hemin; D007501:Iron