Sialorphin and its analog as ligands for copper(II) ions

In this study the sialorphin (Gln-His-Asn-Pro-Arg) and its analog (Glp-His-Asn-Pro-Arg) were analyzed in terms of metal binding ability. Both peptides were synthesized using the solid-phase method. The application of number analytical methods: potentiometry, spectroscopy (UV-Vis, CD, NMR) and mass spectrometry allowed for a detailed characterization of the coordination abilities of presented peptides. The analysis of the obtained results has shown that both peptides are able to form a series of complexes. However due to the presence of free N-terminal amino group the sialorphin is more effective in metal ion binding. Nevertheless, in basic conditions both peptides involve the amide nitrogen belonging to the side chain of Asn3 moiety and form 4N complex with square planar structure. This unusual ability has been confirmed by the results obtained from the NMR studies.