Raman spectroscopy of L‐tryptophan‐containing peptides adsorbed on a silver surface

Surfac‐enhanced Raman spectra of L‐tryptophanylglycine (L‐Trp‐Gly) and L‐tryptophanylglycylglycine (L ‐Trp‐Gly‐Gly) adsorbed on a silver surface were obtained. More detailed investigations than in a previous study on the surface‐enhanced Raman scattering from L‐tryptophan (L‐ Trp) and glycyl‐L‐tryptophan (Gly‐L‐Trp) were also made. It was found that L‐Trp and the above peptides adsorb on the silver surface via both the carboxylate (COO⁻) and the amino (NH₂) groups. Interestingly, the nitrogen atom of the indole ring of L‐Trp was found to bind to the surface only when L‐Trp is the C‐terminal residue.