Computational analysis of binding free energies between peptides and single-walled carbon nanotubes

Coating carbon nanotubes (CNTs) with peptides can solubilize the nanotubes in water solvent. To explore the utilization of CNTs in solvent and the affinities of CNTs for different peptides, binding free energies of peptides to single-walled carbon nanotubes (SWCNTs) are calculated and analyzed. The interactions between different peptides and SWCNTs are simulated using molecular dynamics (MD) methods. The binding free energies of peptides onto the outer-surface of the SWCNTs are then estimated based on thermodynamics theory. The estimated results of binding free energies are qualitatively comparable to binding affinities observed in experiments. Furthermore, the conformations of the binding peptides, as well as the energetic contributions to total binding free energies are analyzed to reveal the physical mechanisms of the interactions, which would be difficult to observe using experimental approaches. The van der Waals interaction is found to play a key role in binding of peptides to SWCNTs. Other effects such as hydrophobicity and aromatic rings of peptides are also examined. The findings of this study provide better understanding of the binding strength between proteins and CNTs, and therefore have potential applications in both scientific research and in industry for controlling CNT self-assembly, designing bio-functionalized CNTs as biosensors, and drug and gene delivery devices.