Direct Electrochemistry and Electrocatalysis of Heme Proteins Entrapped in Agarose Hydrogel Films in Room-Temperature Ionic Liquids

Abstract

The electrochemistry and electrocatalysis of a number of heme proteins entrapped in agarose hydrogel films in the room-temperature ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF(6)]) have been investigated. UV-vis and FTIR spectroscopy show that the heme proteins retain their native structure in agarose film. The uniform distribution of hemoglobin in agarose-dimethylformamide film was demonstrated by atomic force microscopy. Cyclic voltammetry shows that direct electron transfer between the heme proteins and glassy carbon electrode is quasi-reversible in [bmim][PF(6)]. The redox potentials for hemoglobin, myoglobin, horseradish peroxidase, cytochrome c, and catalase were found to be more negative than those in aqueous solution. The charge-transfer coefficient and the apparent electron-transfer rate constant for these heme proteins in [bmim][PF(6)] were calculated from the peak-to-peak separation as a function of scan rate. The heme proteins catalyze the electroreduction of trichloroacetic acid and tert-butyl hydroperoxide in [bmim][PF(6)]. The kinetic parameter I(max) (maximum current at saturation concentration of substrate) and the apparent K(m) (Michaelis-Menten constant) for the electrocatalytic reactions were evaluated.

Modulation of the Silica Sol–Gel Composition for the Promotion of Direct Electron Transfer to Encapsulated Cytochrome c

“…7). In other words, it appears a correlation between reversibility and concentration which has already been reported by other authors 37,55,57 . According to the literature, this behavior can be due to the affinity shown by cyt c to the surface of metal oxide electrodes 58 .…”

Voltammetric Behavior of Bilirubin Based on [bmim][PF6] As the Supporting Electrolyte in Organic Solvent and Its Analytical Application

“…The voltammetric studies were taken using a pretreated GCE as working electrode with an area of approximately 0.057 cm 2 , a platinum wire as auxiliary electrode, and an aqueous saturated calomel electrode (SCE) as reference electrode. The pretreatment of bare GCE was in the same way as described in our previous paper [21]. The controlled potential coulometric measurements were performed using a large electric glass as the working electrode.…”

Electrodeposition CaCO3 Nanoparticles‐chitosan Composite Film on Carbon Ionic Liquid Electrode as a Platform for Hemoglobin Electrochemical Biosensor

“…30 The surface coverage (G*) of Hb on the surface at the Hb-chi/nanoCaCO 3 -chi/ CILE was estimated to be 1.43 × 10 -9 mol·cm -2 by integration of the reduction peak currents of Hb on the CVs in 0.1 mol/L pH 7.0 PBS, which was much larger than that of monolayer coverage (1.89 × 10 -11 mol·cm -2 for Hb). 31 However, the fraction of electroactive proteins among the total proteins deposited at the CILE was of 9.6%. This was always relatively low because only those proteins in the inner layers of the film close to the electrode and with a suitable orientation can exchange electrons with the electrode surface.…”