A Novel Method for Determining the Chelation Ability of the Cysteine-Containing Peptides with 3,4-Toluenedithiol. Application to -Ferredoxin Model Systems

Article abstract of DOI:10.1246/bcsj.60.283

The chelating ability of a bidentate ligand, Cys-X-Y-Cys (X, Y=amino acid residue), in 2Fe-2S peptide model complexes was examined by a ligand-exchange method using 3,4-toluenedithiol (tdt-H2) or o-xylene-α,α'-dithiol.The addition of tdt-H2 to an N,N-dimethylformamide solution of ^2- results in the cleavage pf Fe-S* (S*=inorganic sulfur) bond and in the formation of hydrogen sulfide and mononuclear Fe(III) peptide thiolate complex, ^1-.In the case of (Fe2S2(Z-Ala-cys-OMe)4>^2-, 2>^2- was obtained by the substitution of Z-Ala-Cys-OMe with the chelating reagent.On the other hand , o-xylene-α,α'-dithiol expels both Z-Cys-Ala-Ala-Cys-OMe and Z-Ala-Cys-OMe ligands from these complexes.