Direct electrochemistry and bioelectrocatalysis of myoglobin at a carbon nanotube-modified electrode

Myoglobin (Mb) was immobilized onto the surface of carbon nanotube (CNT) and was characterized by AFM, XPS, UV-Vis, and FTIR spectroscopy. The promotion effect of CNT on direct electron transfer (DET) reaction of Mb was studied. Cyclic voltammetric results showed a pair of well-defined redox peaks, which corresponded to DET of Mb, with the formal potential (E-o') of (-0.343 +/- 0.001) V (vs SCE) in the phosphate buffer solution (PBS, pH 7.0). The electrochemical parameters, such as apparent heterogeneous electron transfer rate constant (k(s)) and E-o', were determined. The dependence of E-o' on solution pH indicated that DET reaction of Mb was coupled with proton transfer. The experimental results also demonstrated that the immobilized Mb retained its bioelectrocatalytic activity toward the reduction of H2O2 and O-2.