We investigate the immobilization of Trametes versicolor (TvL) and the small laccase (SLAC) from Streptomyces coelicolor on single-wall carbon nanotube (SWCNT) surfaces. As we previously reported, SLAC may potentially offer better adsorption characteristics in comparison to TvL, thus improving direct electron transfer (DET). In the approach explored here, which was recently demonstrated experimentally, laccase immobilization on SWCNTs is achieved noncovalently; a molecular tether � 1-pyrene butanoic acid � forms an amide bond with an amine group on the laccase surface while the pyrene coordinates to the SWCNT by p-stacking, as shown previously for streptavidin and ferritin. Density functional theory calculations to model the interaction energies between SWCNTs and pyrene were first performed to validate the COMPASS force-field. In the simulated models, the SWCNT was placed near the region of each laccase close to the Cu(T1) (type 1) atoms, as well as near two other regions of each laccase where adsorption seems likely. Both tethered and untethered systems were simulated using classical molecular dynamics (MD) simulations. The interaction energies between the SWCNTs and the laccase were calculated from the MD equilibrium trajectories in order to draw conclusions on the propensity toward adsorption. The distance between the SWCNT surface and the Cu(T1) atom was monitored as a measure of the likelihood of DET. We found that SWCNTs adsorb more strongly to SLAC than to TvL, and the separation between the SWCNTs and the Cu(T1) atoms are substantially shorter for SLAC than for TvL. Although these results may have implications for DET, experimental limitations in using SWCNT electrode materials have yet to be overcome.

Immobilization of laccases on single-walled carbon nanotube electrodes: A molecular dynamics study

243rd National Meeting (2012)

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