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

Colloids Surf B Biointerfaces. 2022 Sep:217:112660. doi: 10.1016/j.colsurfb.2022.112660. Epub 2022 Jun 25.

Abstract

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 β-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 methionine-rich β-hairpin motif, which is the key binding site for TtLac binding onto the NH2-CNT surface via electrostatic interaction, π-π stacking and cation-π 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.

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

MeSH terms

  • Adsorption
  • Electrodes
  • Laccase* / metabolism
  • Methionine
  • Nanotubes, Carbon* / chemistry

Substances

  • Laccase
  • Methionine
  • Nanotubes, Carbon