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.