Direct electron transfer of horseradish peroxidase (HRP) was achieved by immobilizing HRP on a functional nanocomplex modified glassy carbon (GC) electrode. The cyclic voltammograms (CVs) of the modified electrode have a pair of well-defined redox peaks with a formal potential (E°') of -26 ± 2 mV versus Ag/AgCl, in 0.05 M, pH7.0 phosphate buffer solution (PBS) at a scan rate of 0.05 V/s. The heterogeneous electron transfer constant (ks) was calculated to be 1.94 s-1. The modified electrode response toward hydrogen peroxide was linear in the concentrations ranging from 0.28 μM to 10 μM, with a detection limit of 0.28 μM. The apparent Michaelis-Menten constant (Kmapp) for H2O2 was 2.54 μM. Moreover, results of biochemical computation showed that the amino acid residues (Ala34, Arg38, Ser73, Arg75, Ala140, Pro141, Phe172, Gly173, Lys174, Phe179, Arg31, Ser35, Lys174, Gln176) of HRP may playa crucial role in the improvement of electron transport between electro-active site (heme group) of an HRP molecule and nanocomplex modified GC electrode.
Keywords: Horseradish peroxidase; biochemical computation; carboxylic multi-walled carbon nanotubes; direct electron transfer; gold nanoparticles.