Interaction of the C-terminal peptide from pigeon cytochrome C with silver nanoparticles. A Raman, SERS and theoretical study

Abstract

The Raman and surface-enhanced Raman scattering (SERS) spectra of the C-terminal peptide of pigeon cytochrome C (PCC87–104), were recorded. This peptide is widely used to study the immune response in vivo. Hydrophobicity and net charge parameters of PCC87–104, allowed prediction of the nature of its interaction with colloidal nanostructured silver surfaces. The SERS spectrum provided information about the organization and orientation of PCC87–104 on the surface of silver nanoparticles (AgNPs). The batch to batch reproducible SERS spectra were obtained by adding the colloidal AgNPs solution onto the dried analyte sample. On the basis of the SERS information and the analysis of the net charge of each amino acid residue in the peptide sequence, it is concluded that the interaction of the peptide and the AgNPs is mainly induced and oriented by the lysine residues. The spectroscopic results are supported by quantum chemical calculations, performed by using Extended Hückel theory for a model of PCC87–104 interacting with a silver surface.