Theoretical Insights into the Interaction Mechanism between Protein and SWCNT: Adsorptions of Tripeptides GXG on SWCNT

摘要

Adsorptions of nine tripetides GXG, ranging from negatively (D) and positively (K) charged, to hydrophilic (N and S), and to hydrophobic (G, V, F, W, and Y) residues, on the two cluster models (C54H18 and C54) of (10,0) SWCNT are systemically investigated with MPWB1K and MP2 methods. The solvent effects are taken into account with implicit CPCM model. The objective is to provide novel insights into the interaction mechanism between proteins and single-walled carbon nanotube (SWCNT). Results reveal that the adsorption strength of two charged tripeptides is greatly affected by solvent effect and the Hydrogen-saturability of the SWCNT models. In gas phase, on the surface of C54H18 GKG has the strongest adsorption (Adsorption energy: -29.3 kcal/mol at MP2 level), whereas the adsorption of the negatively charged GDG is the strongest on C54 (AE: -30.4 kcal/mol with MP2). However, because of strong solvation the adsorptions of the charged residues (D and K) on both C54H18 and C54 surfaces in aqueous solution are either rather weak or even unbound. The two neutral hydrophilic residues (N and S) exhibit adsorptions on C54H18 in gas phase (AE: -3.3 and -4.2 kcal/mol), yet unable to adsorb on SWCNT in aqueous solution (AE: +0.3kcal/mol at MP2+CPCM). The five hydrophobic residues present relatively strong adsorption on SWCNT, especially for the three aromatic residues (GFG, GYG and GWG), regardless of CNT models and in gas phase or solution. These results indicate that in general the aromatic groups of proteins would play very important role on functionalizing CNT, which basically support the relevant experimental observations. In addition, the electron correlation is essential for adsorptions of GXG on pristine SWCNT, and the three aromatic residues have the highest electron correlation effects. The present investigation provides a strong evidence that for the functionalization of CNT via proteins it is most likely that hydrophobic interaction and van der Waals are the dominant driving forces.