Studies relating to the ferredoxins. Part 2. Exchange reactions of some cysteine–glycine peptides with the iron–sulphur cluster compound bis(tetramethylammonium) tetrakis(µ3-sulphido-t-butylthioiron)

Abstract

Four peptides of the general structure Ac-Gly₂-(Cys-Gly₂)_n-Cys-Gly₂-NH₂(n= 0–3) have been synthesised. They all exchange readily in dimethyl sulphoxide solution with the title iron–sulphur cluster compound to give peptide iron–sulphur cluster compounds. The exchange reactions have been followed quantitatively by ¹H n.m.r. spectroscopy. The four successive equilibrium constants have been evaluated in the case of the unidentate ligand (n= 0), but the other three cases are too complex for such a treatment.