Resonance Raman and electron paramagnetic resonance studies on oxidized and ferricyanide-treated Clostridium pasteurianum ferredoxin. Vibrational assignments from 34S shifts and evidence for conversion of 4 to 3 iron-sulfur clusters via oxidative damage. Vibrational assignments from 34S shifts and evidence for conversion of 4 to 3 iron-sulfur clusters via oxidative damage.