Optical Properties of Artificial Non-heme Iron Proteins Derived from Bovine Serum Albumin

Three types of artificial non-heme iron proteins can be prepared from bovine serum albumin. Two of these are prepared by incubating serum albumin with iron either in the presence or absence of 2-mercaptoethanol. A third type is prepared by incubating serum albumin with 2-mercaptoethanol, iron, and inorganic sulfide. The latter type resembles ferredoxin spectrally and contains 5 to 8 moles of iron and 4 to 7 moles of inorganic sulfide per mole of protein. This protein-iron-sulfide complex however can be distinguished from the ferredoxin, adrenodoxin, and rubredoxin by comparison of the circular dichroic spectra. The Cotton effects in the 300 to 350 mµ region have been provisionally assigned to electronic transitions arising from the iron-protein interaction, whereas the Cotton effects in 350 to 440 mµ region appear to be related to iron-sulfide interaction.