Interactions between carbon nanotubes and biomolecules: combinatorial routes to specific binding

From a combinatorial library containing billions of sequences, peptides have been selected to provide specific binding interactions with carbon nanotubes, graphitic nanoparticles, and other materials of interest. The binding interaction is selective between nanotube and graphite allotropes of carbon. Since the local bond structure is similar in these materials, the interaction may be distinguishing the larger-scale geometry (curved vs. flat sheets) or the electronic structure (1d metal or semiconductor vs. 2d semi-metal) in nanotubes vs. graphite. Simulation and force spectroscopy provide two approaches to study the interplay of Coulombic, van der Waals, hydrophobic, and steric forces that may contribute to the specific interaction. As a starting point, a multicanonical simulation of the conformation of one peptide under the ECEPP/3 potential set shows evidence of a structural transition at effective temperatures near ambient. This structure, surprising in a short peptide, may be due to the presence of a proline in the center of the amino acid sequence.