Get FE S = fs1 = iron/sulfur cluster Get FE2 S2 = fes = fe2/s2 (inorganic) cluster Get FE3 S4 = f3s = fe3-s4 cluster Get FE4 S3 = sf3 = fe4-s3 cluster Get FE4 S4 = fs4 = iron/sulfur cluster Get FE4 S4 = sf4 = iron/sulfur cluster Get FE8 S7 = clf = fe(8)-s(7) cluster Get FE8 S8 = clp = fe-s cluster