Electrochemical studies of binary and ternary copper(II) complexes with α-factor analogues

Iwona Ufnalska , Urszula Wawrzyniak , K. Bossak-Ahmad , Wojciech Bal , Wojciech Wróblewski

Abstract

Copper(II) binding properties of Saccharomyces cerevisiae pheromone (α-factor) analogues, namely WHWSKNR-am, FHWSKNR-am and WHFSKNR-am amino acid sequences, were studied using voltammetry techniques, fluorescence and UV–Vis spectroscopy. Despite the same 3N binding mode attributed to XHZ-type oligopeptides, the obtained results demonstrated high dependence of the electrochemical properties of their copper(II) complexes on the metal ion coordination environment. Changes triggered by ternary complex formation with imidazole molecule, leading to 4N structure formation, were also examined. The investigated derivatives underwent reduction and oxidation processes as well, however the coordination sphere affected mainly the anodic signal. Different electrochemical responses of α-factor analogues revealed significant influence of tryptophan residue position in a peptide sequence and indicated the complexity of ongoing redox processes. That stems from the presence of two different redox active centers and the possibility of the occurrence of multiple electrostatic interactions engaging charged groups, metal cation and indole moiety.