title: Direct electron transfer and enzymatic activity of hemoglobin in a hexagonal mesoporous silica matrix.
abstract: The direct electrochemistry of hemoglobin (Hb) immobilized on a hexagonal mesoporous silica (HMS)-modified glassy carbon electrode was described. The interaction between Hb and the HMS was investigated using UV-Vis spectroscopy, FT-IR, and electrochemical methods. The direct electron transfer of the immobilized Hb exhibited two couples of redox peaks with the formal potentials of -0.037 and -0.232 V in 0.1 M (pH 7.0) PBS, respectively, which corresponded to its two immobilized states. The electrode reactions showed a surface-controlled process with a single proton transfer at the scan rate range from 20 to 200 mV/s. The immobilized Hb retained its biological activity well and displayed an excellent response to the reduction of both hydrogen peroxide (H2O2) and nitrate (NO2-). Its apparent Michaelis-Menten constants for H2O2 and NO2- were 12.3 and 49.3 microM, respectively, showing a good affinity. Based on the immobilization of Hb on the HMS and its direct electrochemistry, two novel biosensors for H2O2 and NO2- were presented. Under optimal conditions, the sensors could be used for the determination of H2O2 ranging from 0.4 to 6.0 microM and NO2- ranging from 0.2 to 3.8 microM. The detection limits were 1.86 x 10(-9) M and 6.11 x 10(-7) M at 3sigma, respectively. HMS provided a good matrix for protein immobilization and biosensor preparation.
authors.affiliation: Department of Chemistry, Institute of Analytical Science, State Key Laboratory of Coordination Chemistry, Nanjing University, Nanjing 210093, PR China.
authors.forename: Zhihui
authors.initials: Z
authors.lastname: Dai
authors.forename: Songqin
authors.initials: S
authors.lastname: Liu
authors.forename: Huangxian
authors.initials: H
authors.lastname: Ju
authors.forename: Hongyuan
authors.initials: H
authors.lastname: Chen
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation / Q000379:methods*; D002384:Catalysis; D004563:Electrochemistry / Q000295:instrumentation / Q000379:methods*; D004566:Electrodes; D004579:Electron Transport; D004789:Enzyme Activation; D005240:Feasibility Studies; D006454:Hemoglobins / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000032:analysis* / Q000737:chemistry; D008968:Molecular Conformation; D009566:Nitrates / Q000032:analysis* / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry*
chemical_list: D006454:Hemoglobins; D009566:Nitrates; D012822:Silicon Dioxide; D006861:Hydrogen Peroxide