Electrochemistry of heme proteins entrapped in DNA films in two imidazolium-based room temperature ionic liquids

Abstract

Two imidazolium-based ionic liquids (ILs), hydrophilic 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]) and hydrophobic 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]), have been chosen as solvents for investigating bioelectroanalysis of four heme proteins. Heme proteins including hemoglobin, myoglobin, catalase and horseradish peroxidase immobilized in DNA can form stable and electrochemically active films on glassy carbon electrode. The morphology studies of films were demonstrated by atomic force microscopy. The direct electrochemistry of heme proteins were performed in ILs, and a pair of well-defined and nearly reversible redox peaks were observed. The electron transfer rate and reversibility of heme proteins in [bmim][BF4]/water were better than those in [bmim][PF6]. Through comparing several electrochemical parameters such as formal potentials and electron transfer rate constant of proteins in ILs, this paper tried to explain the differences of electrochemical properties of proteins as a function of viscosity, solubility characteristics, etc. of ILs. The possibility to specifically vary the properties of ILs by the selection of suitable cations and anions make them ideal candidates for wide applications in cell biological processes.