Copper and nickel complex-formation equilibria with Lys-Gly-His-Lys, a fragment of the matricellular protein SPARC

摘要

Complex-formation equilibria of the tetrapeptide Lys-Gly-His-Lys with the Cu(II) and the Ni(II) ions have been studied in aqueous solution, at I=0.1 mol dm(-3) (KNO3) and T=25degreesC. Protonation and complex-formation constants have been potentiometrically determined. The structure of the main complex species is discussed on the basis of thermodynamic data obtained by direct calorimetry as well as the CD, ESR and electronic spectra. The participation of two amide nitrogens in complex-formation is suggested for both the metal ions, while no evidence supports the participation of the epsilon-NH2 side groups of Lys residues in coordination. (C) 2002 Elsevier Science Ltd. All rights reserved. [References: 19]