Pre-equilibrium Determining the Rate and Selectivity in the Ligand-exchange of Cu(II) Complex, Cu(II)(H−2Gly-Gly-X), with Cysteine to Yield a Ternary Complex, (Cys)N,SCu(II)(H−1Gly-Gly-X)

Abstract

Abstract Equilibrium constant for the reaction of Cu(II)(H−2Gly-Gly-X) with N-acetyl-l-cysteine to yield a ternary complex, (AcCys)SCu(II)(H−2Gly-Gly-X), was determimed. A linear free energy relationship existed between this equilibrium constant and rate constant for the ligand-exchange with l-cysteine to form a ternary complex, (Cys)N,SCu(II)(H−1Gly-Gly-X), indicating the presence of pre-equilibrium state in the ligand-exchange reaction.