title: EPR studies of protein state transitions in Chromatium ferricytochrome c'.
abstract: Recent magnetic studies have shown that in the pH range 1 to 11 the bacterial heme protein ferricytochrome c' can undergo reversible transitions between various pure high-spin and quantum mechanically mixed (intermediate and high)-spin protein states. The EPR data presented here extend the recent work to high alkaline pH and show that above pH 11.6 reversible transitions occur between various pure high-spin and pure low-spin protein states. The new data and the previous magnetic studies of the protein are discussed in the context of the entatic nature of the iron-porphyrin complex in ferricytochrome c'. EPR data are also provided concerning an anomalous, but reversible, transition to a protein state with reduced heme iron, triggered by freezing and thawing at physiological pH.
mesh_terms: D002844:Chromatium; D003574:Cytochrome c Group; D004578:Electron Spin Resonance Spectroscopy; D005615:Freezing; D006420:Hemeproteins; D006863:Hydrogen-Ion Concentration; D007501:Iron; D011487:Protein Conformation
chemical_list: D003574:Cytochrome c Group; D006420:Hemeproteins; D007501:Iron