Gold single-crystal electrode surface modified with self-assembled monolayers for electron tunneling with bilirubin oxidase

Abstract

Using Au(111) and Au(100) single-crystal electrodes modified with self-assembled monolayers (SAMs), the direct electron transfer reaction of bilirubin oxidase (BOD) adsorbed onto their surfaces was investigated. The BOD adsorbed onto the Au(111), Au(100) and gold /mica electrodes, and the BOD adsorbed onto Au(111) electrodes modified with C(3)-SO(3)H and C(n)-COOH (n = 2, 5 and 7), showed the electrocatalytic currents of dioxygen reduction based on the direct electron transfer reaction. The BOD adsorbed onto Au(111) electrodes modified with C(6)-NH(2), C(6)-OH and C(5)-CH(3) did not show any electrocatalytic current. Negatively charged electrode surfaces can give a suitable molecular orientation for the direct electron transfer of BOD. The k degrees values evaluated by an analysis of the steady-state voltammogram with a simulated fitting method did not depend on the crystal structure of the gold electrode surface. Using a C(n)-COOH (n = 2, 5, 7) modified Au(111) electrode, the k degrees values decreased with an increasing alkyl chain length of C(n)-COOH. Based on the k degrees values obtained from the C(n)-COOH (n = 2, 5, 7) modified Au(111) electrodes, the electron tunneling distance was evaluated. The average distance between the type 1 Cu site of BOD and the outside of the BOD protein structure was evaluated to be 17 (+/-2) A.

Biohydrogen for a New Generation of H2/O2 Biofuel Cells: A Sustainable Energy Perspective

“…[47] A clearer situation was obtained upon immobilization of Mv BOD on gold single-crystal electrodes. [158,177] CV coupled to QCM and AFM experiments at various SAMs confirmed that hydrophilic interfaces, and especially negative interfaces, were more favorable for T1 interaction and electrocatalysis of O 2 reduction. A different orientation on bare gold vs. SAM-modified gold was suggested.…”

An overview of dealloyed nanoporous gold in bioelectrochemistry

“…Previous reports have described DET of BOD on bare or negatively charged SAMs modified single-crystal electrodes [101] and three-dimensional AuNP electrodes [102]. BOD was physically embedded into bare NPG and the resulted electrodes displayed bioelectrocatalytic reduction of molecular oxygen, undergoing efficient DET (Figure 8) [76].…”

Voltammetry and Single-Molecule in Situ Scanning Tunneling Microscopy of Laccases and Bilirubin Oxidase in Electrocatalytic Dioxygen Reduction on Au(111) Single-Crystal Electrodes

“…The catalysis of O 2 reduction by this enzyme has been studied several times. DET 53 Catalytic currents were found for bare (single-crystal) gold and gold modified with different SAMs. Negatively charged SAMs (ÀCOOH and ÀSO 3 À ) were found to give catalytic current, whereas SAMs terminated by ÀCH 3 , ÀOH, or ÀNH 2 did not show any.…”