Reduction of Ferricytochrome c by Some Free Radical Agents

Science  01 Feb 1974:
Vol. 183, Issue 4123, pp. 428-430
DOI: 10.1126/science.183.4123.428


Fast pulse radiolysis and kinetic spectroscopy were used to rapidly generate a variety of free radicals in situ and study their reactions with ferricytochrome c in the time range 10-6 to 1 second. The radicals included t-butanol, which is inert to ferricytochrome c; malate, lactate, and ethanol, which react with it relatively slowly but are completely utilized in reducing it to ferrocytochrome c; and hydrated electrons and hydrogen atoms, which react with it very rapidly but yield ferrocytochrome c only in part, showing intramolecular consecutive reactions and further attack on the ferrocytochrome c protein. From a detailed comparison between malate and hydrogen atoms it is argued that malate reacts directly and selectively with a specific part of the ferricytochrome c surface while hydrogen atoms react with other parts of the protein too, yielding radicals which in part transfer intramolecularly to yield ferrocytochrome c.