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 [Fe2S2(Z–cys–Ala–Ala–cys–OMe)2]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, [Fe(Z–cys–Ala–Ala–cys–OMe)(tdt)]1−. In the case of [Fe2S2(Z–Ala–cys–OMe)4]2−, [Fe2S2(tdt)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.
一种双齿
配体 Cys–X–Y–Cys(X, Y=
氨基酸残基)在 2Fe–2S 肽模型复合物中的螯合能力通过
配体置换法进行了研究,该方法使用了 3,4-
甲苯二
硫醇(tdt-H2)或
邻二甲苯-α,α′-二
硫醇。将 tdt-H2 添加到
N,N-二甲基甲酰胺溶液 [Fe2S2(Z–cys–Ala–Ala–cys–OMe)2]2− 中,会导致 Fe–S*(S*=无机
硫)键的断裂,并生成
硫化氢和单核 Fe(III) 肽
硫醇配合物 [Fe(Z–cys–Ala–Ala–cys–OMe)(tdt)]1−。在 [Fe2S2(Z–Ala–cys–OMe)4]2− 的情况下,通过用螯合试剂替代 Z–Ala–Cys–OMe,得到了 [Fe2S2(tdt)2]2−。另一方面,
邻二甲苯-α,α′-二
硫醇会将 Z–Cys–Ala–Ala–Cys–OMe 和 Z–Ala–Cys–OMe
配体从这些复合物中排出。