Electron transfer within and between haemoprotein molecules

Electron Transfer to Ferricytochrome c : Reaction with Hydrated Electrons and Conformational Transitions Involved

“…have recently proposed a mechanism for the electron transfer to cytochrome c (6). This mechanism was based on the transient free-radical model originated by Winfield (7), and is compatible with the information obtained by both chemical modification and structural studies (6).…”

“…At least five traces were analyzed for every rate constant or point in the spectrum. RESULTS Neutral solutions of horse-heart cytochrome c (pH [6][7] After the electron pulse, fast transmittance changes were observed over the whole wavelength range studied, namely, from 350 to 750 nm. In the region between 600 and 750 nm, these changes were mainly due to the appearance and decay of hydrated electrons, which have a very broad absorption band centered at 720 nm (9,13).…”

A role for chloride in the autoxidation of hemoglobin under conditions similar to those in erythrocytes

“…In some abnormal hemoglobins this autoxidation may be more extensive and/or more permanent leading to various forms of methemoglobinemia [2]. Although there have been some proposals concerning the mechanism of methemoglobin formation in specific instances [3] there is still very little understanding of the processes by which hemoglobin undergoes autoxidation [4]. However, our recent observation that a variety of anions are able to promote the autoxidation of hemoglobin through a proton assisted nucleophilic displacement of superoxide from oxyhemoglobin [5] may provide some insight into these physiologically important processes.…”

Electron Transfer Reactions in Biological Systems: The Reduction of Ferricytochrome c by Chromous Ions

“…For example, on the basis of model studies, Winfield (27,28) proposed a mechanism that would involve the participation of a phenylalanine or tyrosine. Since these residues can be induced to form free radicals-and, consequently carry an electron-one of these residues in proximity to the heme could act as an intermediary between the oxidizing agent and the metal ion.…”