The metal-conjugated peptide nucleic acid challenge

This Account describes the advances in the chemistry of metal-conjugated peptide nucleic acids (PNAs) obtained in our laboratories over the last three years. Our interest in bioorganometallic chemistry began several years ago and led to new PNA research, including the design, synthesis and study of the properties of metal-conjugated PNAs with the aim of providing new molecules with suitable spectroscopic or electrochemical markers that may be useful in biomedical diagnostics. We describe three classes of metal-conjugated PNA monomers: Fischer-type carbene complexes (FTC), arene chromium tricarbonyl complexes (ACT) and ferrocene (Fc), all of which are inserted on the alpha-carbon of the glycine unit in order to provide chiral substrates as well as the chemical and spectroscopic properties of the adducts. In addition, we have obtained a lysine-containing PNA 10-mer conjugated to a FTCC, in which the presence of the organometallic unit seems to stabilise the duplex with a complementary DNA strand. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) studies of mono- and tris-Fc labelled tyrosine PNA monomers have shown constantly reversible signals with high currents; the almost tripled current intensity of the tris-Fc monomer allows a detection limit of 10(-8).