Direct electrochemistry of hemoglobin in cetylpyridinium bromide film: Redox thermodynamics and electrocatalysis to nitric oxide

Hemoglobin was successfully immobilized in cetylpyridinium bromide (CPB) film on a polyacrylamide (PAM) modified glassy carbon electrode (GC). Cyclic voltammetry showed a pair of well-defined and nearly reversible CV peaks at about −0.2165 V vs SCE (pH = 4.22), indicating the character of Hb heme Fe(II)/heme Fe(III) redox couple. The apparent standard potentials of hemoglobin in the CPB were linearly varied with pH in the range from 4.22 to 9.18 with a slope of −48.85 mV pH−1, implying that one proton was accompanied with one electron transferred in the electrochemical reaction. The adsorption of Hb on the surface of PAM/GC electrode have been investigated by electrochemical impedance spectroscopy. The apparent standard potentials of hemoglobin were also studied through direct electrochemistry method as a function of temperature and the thermodynamic parameters (ΔSrc and ΔHrc) for the protein redox were calculated. Hemoglobin in the CPB exhibited catalytic activity for electrochemical reduction of NO.