A Non-G-Quadruplex Hemin Aptamer Forms a Better Peroxidase Mimicking DNAzyme.

G-quadruplex DNA is known to bind to hemin, forming a complex that exhibits peroxidase-like activity. A non-G-quadruplex aptamer named Hem1-2T also exhibits horseradish peroxidase (HRP) like activity upon binding to hemin. Herein, the catalytic characteristics of the Hem1-2T aptamer are studied and compared with PS2.M, an extensively studied G-quadruplex. From pH 6-8, the activity of Hem1-2T decreases with the increase in pH, which is similar to HRP, whereas the activity of PS2.M increases with pH, suggesting that Hem1-2T might be a better mechanistic mimic of HRP. Additionally, Hem1-2T is more effective at protecting hemin from degradation by H2O2, as evidenced by a slower decrease in the absorbance at 404 nm compared to PS2.M and more sustained catalysis. NMR spectroscopy indicates that hemin promotes ligand-induced structure formation in the Hem1-2T aptamer and forms a specific complex, whereas hemin interacts with the PS2.M G-quadruplex in a way leading to the disappearance of NMR peaks. Overall, the Hem1-2T-hemin complex is a better and more stable HRP mimic, supporting its potential applications in bioanalysis and biocatalysis.