Electron-Transfer Reactivity and Enzymatic Activity of Hemoglobin in a SP Sephadex Membrane

Abstract

Hemoglobin can exhibit a direct electron-transfer reaction after being entrapped in a SP Sephadex membrane. A pair of stable and well-defined redox waves are obtained at a hemoglobin−SP sephadex modified pyrolytic graphite electrode. The anodic and cathodic peak potentials are located at −0.244 and −0.336 V (vs SCE), respectively. On the other hand, the peroxidase activity of the protein in the membrane is also greatly enhanced. The apparent Michaelis−Menten constant is calculated to be 1.9 mM, which shows a large catalytic activity of hemoglobin in the SP Sephadex membrane toward hydrogen peroxide (H₂O₂). According to the direct electron-transfer property and enhanced peroxidase activity of Hb in the membrane, a Hb/SP Sephadex membrane-based H₂O₂ biosensor is prepared, with a linear range ∼5.0 × 10^-6 to 1.6 × 10^-4 mol/L.