Copper complexes of dipeptides with L-Lys as C-terminal residue: a thermodynamic and spectroscopic study

Complex-formation equilibria of some dipeptides (glycyl-lysine, alanyl-lysi ne, histidyl-lysine and beta -alanyl-lysine) with the Cu(II) ion have been studied in aqueous solution, at I = 0.1 mol dm(-3) (KNO3) and T = 25 degree sC. Protonation and complex-formation constants have been determined potent iometrically; complex-formation model and species stoichiometry have been c hecked carefully by means of different spectroscopic techniques (visible ab sorption, CD, EPR). The structure of the main complex species is discussed, on the basis of thermodynamic data obtained by direct calorimetry. The for mation of binuclear species is demonstrated and it is suggested that the si de amino group of lysine participates in complex formation at alkaline pH v alues. (C) 2000 Elsevier Science B.V. All rights reserved.