Direct electrochemistry and electrocatalysis of heme-proteins entrapped in agarose hydrogel films.
Three heme-proteins, including myoglobin (Mb), hemoglobin (Hb) and horseradish peroxidase (HRP), were immobilized on edge-plane pyrolytic graphite (EPG) electrodes by agarose hydrogel. The proteins entrapped in the agarose film undergo fast direct electron transfer reactions, corresponding to FeIII = e- --> FeII. The formal potential (E degrees'), the apparent coverage (Gamma), the electron transfer coefficient (alpha) and the apparent electron transfer rate constant (ks) were calculated by integrating cyclic voltammograms or performing nonlinear regression analysis of square wave voltammetric (SWV) experimental data. The E degrees's are linearly dependent on solution pH (redox Bohr effect), indicating that the electron transfer was proton-coupled. Ultraviolet visible (UV-Vis) and reflection-absorption infrared (RAIR) spectra suggest that the conformation of proteins in the agarose film are little different from that proteins alone, and the conformation changes reversibly in the range of pH 3.0-10.0. Atomic force microscopy (AFM) images of the agarose film indicate a stable and crystal-like structure formed possibly due to the synergistic interaction of hydrogen bonding between N,N-dimethylformamide (DMF), agarose hydrogel and heme-proteins. This suggests a strong interaction between the heme-proteins and the agarose hydrogel. DMF plays an important role in immobilizing proteins and enhancing electron transfer between proteins and electrodes. The mechanisms for catalytic reduction of hydrogen peroxide and nitric oxide (NO) by proteins entrapped in agarose hydrogel were also explored.
Liu
Hui-Hong
HH
Department of Chemistry, Wuhan University, Wuhan 430072, China.
Tian
Zhi-Quan
ZQ
Lu
Zhe-Xue
ZX
Zhang
Zhi-Ling
ZL
Zhang
Min
M
Pang
Dai-Wen
DW
D000042:Absorption; D001672:Biocompatible Materials; D015374:Biosensing Techniques / Q000379:methods*; D002384:Catalysis; D004563:Electrochemistry / Q000379:methods*; D006420:Hemeproteins / Q000032:analysis* / Q000737:chemistry*; D020100:Hydrogels / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008422:Materials Testing; D009569:Nitric Oxide / Q000737:chemistry; D010084:Oxidation-Reduction; D011485:Protein Binding; D012685:Sepharose / Q000737:chemistry*
D001672:Biocompatible Materials; D006420:Hemeproteins; D020100:Hydrogels; D009569:Nitric Oxide; D012685:Sepharose; D006861:Hydrogen Peroxide