Sequence specific association of tryptic peptides with multiwalled carbon nanotubes: effect of localization of hydrophobic residues

A model-free approach has been used to study the association of peptides onto multiwalled carbon nanotubes (MWCNT) in aqueous solution at ambient pH to understand the molecular basis of interaction of the peptides with MWCNT. The peptides obtained by tryptic digestion of cytochrome P450cam from P. putida were allowed to interact with MWCNT, and several peptides were found to bind to the nanotube leading to formation of stable homogeneous dispersion of the bionano conjugates of MWCNT. The peptides bound to the MWCNT were separated from the unbound peptides and sequence analyses by tandem MS/MS technique identified the strongly bound peptides as well as the unbound and the weakly bound peptides. The peptide-MWCNT conjugate was further characterized by TEM as well as Raman, FTIR, vis-NIR absorption, and circular dichroism spectroscopy. A model based on the hydrophobicity of residues in the peptides suggested that the amphiphilic peptides with localized hydrophobic residues at the center or at one end of the sequence form stable dispersions of the peptide-MWCNT conjugates.