Interfacial Behavior and Activity of Laccase and Bilirubin Oxidase on Bare Gold Surfaces

Abstract

Two blue multicopper oxidases (MCOs) (viz. Trametes hirsuta laccase (ThLc) and Myrothecium verrucaria bilirubin oxidase (MvBOx)) were immobilized on bare polycrystalline gold (Au) surfaces by direct adsorption from both dilute and concentrated enzyme solutions. The adsorption was studied in situ by means of null ellipsometry. Moreover, both enzyme-modified and bare Au electrodes were investigated in detail by atomic force microscopy (AFM) as well as electrochemically. When adsorbed from dilute solutions (0.125 and 0.25 mg mL −1 in the cases of ThLc and MvBOx, respectively), the amounts of enzyme per unit area were determined to be ca. 1.7 and 4.8 pmol cm −2 , whereas the protein film thicknesses were determined to be 29 and 30 Å for ThLc and MvBOx, respectively. A wellpronounced bioelectrocatalytic reduction of molecular oxygen (O 2 ) was observed on MvBOx/Au biocathodes, whereas this was not the case for ThLc-modified Au electrodes (i.e., adsorbed ThLc was catalytically inactive). The initially observed apparent k cat app values for adsorbed MvBOx and the enzyme in solution were found to be very close to each other (viz. 54 and 58 s −1

Transparent and flexible, nanostructured and mediatorless glucose/oxygen enzymatic fuel cells

“…5A). Following our recent report, one could suggest that the poor stability of the biocathodes was, in all likelihood, attributable to BOx deactivation on the bare Au surface [34], whereas CDH was protected from the metal surface by the thiol layer.…”

Controlling Redox Enzyme Orientation at Planar Electrodes

“…Recovering of the catalytic signal for H 2 oxidation after surfactant addition in the R. eutropha Hase sample suggested that the absence of a surfactant compared to the A. aeolicus Hase sample induced structural changes of the enzyme because of the strong electrostatic interactions. LAC and BOD immobilized for DET on gold electrodes were shown to face potential-induced structural changes as revealed by SERRS and ellipsometry experiments [58,141]. QCM and dual-polarization interferometry studies of BOD immobilized on negative SAM-based gold electrodes highlighted that deformation required for DET should lead to a decrease in activity at high enzyme concentrations [146].…”

“…Hence, polycrystalline gold surfaces, where the distribution of metal atoms is nonuniform throughout the electrode surface, are very handy. Surface treatment provides surface control and promotes their wide use for protein electrochemistry [58]. Electrochemical cleaning by cycling in H 2 SO 4 solution between −0.35 V and +1.5 V vs. Ag/AgCl allows calculating of the real electroactive surface area by integrating the gold oxide reduction peak at +0.9 V, taking into account a charge of 390 µC·cm −2 for the reduction of a gold oxide monolayer [59].…”

Role of 2-mercaptoethanol in direct electron transfer-type bioelectrocatalysis of fructose dehydrogenase at Au electrodes

“…When enzymes adsorb on a solid electrode, enzymes might tend to denature and to lead to decrease in their catalytic functions due to conformational change [5][6][7][8]. Elucidation of the adsorbed enzyme conditions and controlling of the adsorption state will lead to improvement in the DET-type catalytic performance and a wide variety of its applications, such as biosensors and biofuel cells.…”