The low temperature NMR reoxidation pattern of Desulfovibrio gigas cytochrome C 3 has been studied and the resonance corresponding to intermediate reoxidation studies assigned to the methyl resonance in the oxidized position. These assignments allow the proposition of a model which takes in account all the species present during the reoxidation. The interaction between D. gigas cytochrome C 3 (Mr 13,000) and other proteins (rubredoxin and flavodoxin) from the same organism was done by NMR. Selective shifts and broadenings were observed in the heme methyl resonances upon titration. The reoxidation pattern of D. gigas cytochrome C3 is significantly altered by the interacting protein. D. gigas desulforedoxin was studied by Mossbauer and EPR. It contains two iron atoms in environments non-distinguishable by these techniques and the electronic structure of the chromophore is influenced by stereochemical constrains of the protein. The tetrameric form of D. gigas ferredoxin FdII was studied with Mossbauer and EPR, demonstrating and the presence of a spin coupled structure containing 3 Fe atoms. The progresses obtained allow a better understanding of the mechanism of electron transfer both for cytochromes and iron-sulfur proteins. We are testing our results for their physiological relevance.