Gas-phase stabilized metal complexes of cyclic peptides – theoretical versus experimental study.

This article deals with the experimental and theoretical study of the coordination ability and processes of glycyl-penta and hexahomopeptides and corresponding cyclic derivatives with the AgI, ZnII, and CuII. Special attention is focused on the observed cyclic small peptide analogues as well as corresponding complexes. These phenomena are studied experimentally by electrospray ionization and matrix-assisted laser desorption ionization mass spectrometric methods. Considering the physical and chemical properties of gas-phase stabilized systems, precisely calculated thermodynamic parameters, physical properties, and structures by the quantum chemical DFT methods are performed. Conformational preferences of the obtained peptide species as well as the complexes are presented. The coordination ability is elucidated in condense phase by electronic absorption, infrared, and Raman spectroscopies, nuclear magnetic resonance, and thermal methods. The AgI/AgIII redox process observed during the interaction with the peptides is discussed. [ABSTRACT FROM PUBLISHER]