REDOX PROPERTIES OF 2[4FE-4S] FERREDOXINS

The redox properties of the 2[4Fe-4S] ferredoxin isolated from Clostridium pasteurianum were examined directly at an edge pyrolytic graphite electrode using square-wave voltammetry. The direct electrochemical approach was compared with other techniques that have been used to determine the equilibrium reduction potential of this protein. A microcell is described that permits routine electrochemical experiments on small sample volumes (25-50-mu-l). The electrostatic potentials of a homologous ferredoxin with a known x-ray crystal structure, which includes the first treatment of net atomic charges in the iron-sulfur clusters, was determined using a macroscopic electrostatic model.