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The impact of two –GlyProGly– motifs on formation of di-copper complexes by His4-cyclopeptides†
Abstract
The interactions of copper(II) ions with the macrocyclic peptide, c(HKHGPG)2, were investigated in aqueous solution as a function of pH by potentiometric titration, spectroscopic (UV-Vis, CD, and EPR) and mass spectrometry (ESI-MS) measurements. The experiments were conducted for two different ligand to metal ratios: 1 : 1 and 1 : 2. The present study reveals that below pH 6 only mononuclear complexes exist in the case of both systems (L : Cu(II) = 1 : 1, L : Cu(II) = 1 : 2). However, in an alkaline medium dinuclear forms are preferred, which are dominant in the system containing two equiv. of copper(II). Under basic conditions the {2NIm, 2Nam−} coordination mode is favored. Furthermore, a molecular modeling study was performed in order to characterize structural aspects of the formation of di-copper(II) complexes by His4-cyclopeptides. The comparison of coordination properties of c(HKHP)2 and c(HKHGPG)2 allowed to characterize the impact of two –GlyProGly– motifs on formation of di-copper complexes by His4-cyclopeptides.
- This article is part of the themed collection: Bioinspired systems in supramolecular chemistry and nanotechnology
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