Oxidized Rubredoxin Models. Iron(III) Complexes of Z–Cys–Ala–Ala–Cys–OMe and Z–Ala–Cys–OMe

Oxidized rubredoxin models using Fe(III) ion and cysteine-containing peptide as Z–Cys–Ala–Ala–Cys–OMe were synthesized in solution and characterized by the absorption, CD, MCD, and EPR spectra. The Fe(III)/Z–Cys–Ala–Ala–Cys–OMe complex exhibits similar CD spectra as well as absorption, MCD, EPR spectra to native oxidized rubredoxin. Thus, the model complex has a similar electronic configuration and core structure to that of native protein. From the comparison with the result of Fe(III)/Z–Ala–Cys–OMe complex, the tetrapeptide complex probably has a relatively stable chelate structure with the hairpin turn conformation of the tetrapeptide.