Electron-transfer reactivity and enzymatic activity of hemoglobin in a SP Sephadex membrane.

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 (H 2 O 2 ). According to the direct electron-transfer property and enhanced peroxidase activity of Hb in the membrane, a Hb/SP Sephadex membrane-based H 2 O 2 biosensor is prepared, with a linear range ∼5.0 x 10 -6 to 1.6 × 10 -4 mol/L.