Comparison of Kinetics of Hemoglobin Electron Transfer in Solution and Immobilized on Electrode Surface

The electron transfer properties of horse heart hemoglobin are compared using a hydrophilic indium tin oxide electrode and a dilaurydimethylammonium bromide (DDAB) polymer modified PG electrodes. A clear, stable and quasi-reversible redox curve of hemoglobin (Hb) was obtained in the absence of electron transfer mediators or promoters. The formal redox potential of -0.17 vs. Ag/AgCl of Hb was determined. The effects of the sixth axial binding ligands including cyanoand azido binding ligands on the redox properties of Hb were investigated. There are no significant impacts of these ligands on the redox properties of Hb, whereas big effects of the binding ligand on the electrochemical properties of myoglobin were reported. The cyclic voltammetric behavior of hemoglobin was also studied in a DDAB film coated on a pyrolytic graphite electrode. Surface immobilized Hb in DDAB film gave direct, quasi-reversible, nondiffusion-kinetic-controlled electron transfer on the electrode surface. The formal redox potential for Hb in the DDAB film negatively shifted about 140 mV as compared to the diffusion-controlled redox reaction of Hb.