Monolithic Peptide-Nucleic Acid Hybrid Functioning as an Artificial Microperoxidase

A new peptide nucleic acid (PNA) with an installed peroxidase function has been developed. Fmoc solid phase peptide synthesis prepared a PNA hybrid (VQKCAQCHTVE-(C₂H₄O)₂CH₂-[PNA(T)]₆-G) that renders the microperoxidase backbone, followed by reconstitution with hemin. The resulting holocompound catalyzed the oxidation of 3,3′,5,5′-tetramthylbenzidine by H₂O₂ to 50% that of natural microperoxidase-11, whereas the apo-form and hemin gave no responses. The peroxidase domain was found to be active toward direct electrochemistry and the PNA hybrid served for gene sensor; in the presence of the target DNA (5′-CATGTATAAAAAA-3′), an electrode-attached DNA probe (5′-TsTsTsTsTsTCTCATACATG-3′) showed the ferric-to-ferrous quasi-reversible wave (-276 mV vs Ag/AgCl) through sandwich hybridization. Moreover, the hybridization product could accept H₂O₂ as an oxidant to enhance the reduction current, which occurred likely based on the iron(II)-center-recycling with specific rate constant of 0.19 s^-1.