Bicyclopeptides: a new class of ligands for Cu(II) ions.

There is growing interest in bicyclic peptides among scientists. This group of compounds has more advantageous properties than monocyclic ligands and their application in medicine and biological sciences is possible. It is known that sometimes the presence of metal ions is crucial for the activity of peptides in biological systems, like in the case of oxytocin or vasopressin. Therefore, in this study, we performed a series of experiments with the new bicyclic peptide c(PKKHP-c(CFWKTC)-PKKH) (BCL) that was designed and synthesized by a fully automated induction-assisted solid phase synthesizer. We analyzed the coordination abilities of BCL relative to copper(II) ions. The new bicyclic peptide contains two histidine moieties, separated by proline residues, with two distinct sites for metal ion coordination. The obtained results showed that in all analyzed systems both mono- and dinuclear complexes are formed.