Surface‐enhanced Raman scattering study of L‐tryptophan

Surface-enhanced Raman scattering (SERS) spectra of tryptophan (Trp) were obtained. A unique SERS spectrum of Trp,corresponding to the most stable conformation and orientation on the metal surface, is observed after a stabilization period.The Trp molecules interact with the surface through both the carboxylate and amino groups; the aliphatic moiety is close tothesurface.Thepyrroleringoftheindolemoietyisfartherfromthesurfacethanthebenzenefragment.Theobservedspectravarydependingonboththepreparationofthesilvercolloidandtheaggregationtime.Theinterpretationoftheexperimentalresultsissupportedbytheoreticaltreatmentofthemoleculeonthesilversurface. Copyright