4.7 Article

Modulating the adsorption orientation of methionine-rich laccase by tailoring the surface chemistry of single-walled carbon nanotubes

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ELSEVIER
DOI: 10.1016/j.colsurfb.2022.112660

关键词

Direct electron transfer; Enzymatic biofuel cell; Protein adsorption; Molecular simulation; Laccase; Carbon nanotube

资金

  1. National Natural Science Foundation of China, China [21776093, 21376089]
  2. SCUTGrid at South China University of Technology

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This study provides atomic-scale insights into the direct electron transfer behavior of TtLac on modified-CNT electrode surfaces, revealing that electrostatic modification is an effective way to control the behavior. The positively charged NH2-CNT surface can trigger the direct electron transfer process by interacting with the key binding site of TtLac, leading to its stability and catalytic efficiency.
Achieving fast electron transfer process between oxidoreductase and electrodes is pivotal for the biocathode of enzymatic biofuel cells (EBFCs). However, in-depth understanding of the interplay mechanism between enzymes and electrode materials remains challenging when designing and constructing EBFCs. Herein, atomic-scale insight into the direct electron transfer (DET) behavior of Thermus thermophilus laccase (TtLac) with a special methionine-rich beta-hairpin motif adsorbed on the carboxyl-functionalized carbon nanotube (COOH-CNT) and amino-functionalized carbon nanotube (NH2-CNT) surfaces were disclosed by multi-scale molecular simulations. Simulation results reveal that electrostatic modification is an effective way to tune the DET behavior for TtLac on the modified-CNTs electrode surface. Surprisingly, the positively charged TtLac can be attracted by both negatively charged COOH-CNT and positively charged NH2-CNT surfaces, yet only the latter is capable to trigger the DET process due to the 'lying-on' adsorption orientation. Specifically, the T1 copper site is near the methioninerich beta-hairpin motif, which is the key binding site for TtLac binding onto the NH2-CNT surface via electrostatic interaction, 7C-7C stacking and cation-7C interaction. Moreover, TtLac on the NH2-CNT surface undergoes less conformational changes than those on the COOH-CNT surface, which allows the laccase stability and catalytic efficiency to be well preserved. These findings provide a fundamental guidance for future design and fabrication of methionine-rich laccase-based EBFCs with high power output and long lifespan.

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