| Artificial oligopeptides with pyridyl-derived ligands have been synthesized that are analogous to peptide nucleic acid. Pyridine (py)- and 2,2'-bipyridine (bpy)-functionalized oligopeptides were prepared by traditional solid-phase methods. Spectrophotometric titrations with Cu2+ and Fe2+ show that the oligomers bind stoichiometric quantities of transition metals based on the number of pendant ligands. In the case of a bpy tripeptide, the titration stoichiometry and mass spectra indicate that the metal ions form interstrand crosslinks between two oligopeptides, creating duplex structures linked exclusively by metal ions. To increase product quantity, solution-phase protocols, similar to those used in dendrimer synthesis, were investigated. Using this synthetic methodology, two palindromic, heterofunctional artificial tripeptides were prepared. In the case of a py-bpy-py tripeptide, supramolecular, multi-metallic structures are created by chelation of metal ions with the central bpy moiety and coordination of inorganic complexes with the pendant py ligands. The spectroscopic and electrochemical signatures of these assemblies confirm the expected number of inorganic species in these assemblies. The preparation of an artificial tripeptide with 2,2':6',2''-terpyridine (tpy) and bpy (i.e., tpy-bpy-tpy) was prepared analogously to py-bpy-py, and these two tripeptides form a duplex in the presence of Cu 2+ ions, creating a complementary oligopeptide pair. |
