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-(C2 H4 O)2 CH2 -[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 H2 O2 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 H2 O2 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 .