Electron transfer reactivity and catalytic activity of structurally rigidized hemoglobin

A simple and novel strategy to obtain the direct electrochemistry of hemoglobin (Hb) was reported by enhancing its structural rigidity, which was demonstrated by the great promotion of the electron-transfer reactivity of the protein and its catalytic activity toward hydrogen peroxide (H2O2). Direct fast electron transfer between this structural rigidity enhanced Hb (SRE Hb) and a pyrolytic graphite (PG) electrode was achieved, and a pair of well-defined, quasi-reversible redox peaks were obtained. The cathodic and anodic peaks were located at −0.370 and −0.290 V, respectively. Meanwhile, the catalytic activity of the protein toward the reduction of H2O2 was also studied, and a H2O2 biosensor was subsequently prepared. Its detection limit was 3.4 × 10−7 M with a sensitivity of 0.0224 μA per μM of H2O2. The apparent Michaelis–Menten constant was calculated to be 107 μM, which was lower than those of many horseradish peroxidase based H2O2 sensors, suggesting that structural rigidity of Hb could endow the protein a high peroxidase activity.