Far-infrared amide IV-VI spectroscopy of isolated 2- and 4-Methylacetanilide.

摘要: Delocalized molecular vibrations in the far-infrared and THz ranges are highly sensitive to structure, as well intra- inter-molecular interactions. Thus, spectroscopic studies of biomolecular structures can greatly benefit from an extension conventional mid-infrared wavelength range. In this work, conformer-specific gas-phase spectra two aromatic molecules containing peptide –CO–NH– link, namely, 2- 4-Methylacetanilide, investigated. The planar conformations with trans configuration link have only been observed supersonic-jet expansion. corresponding signatures associated moiety, so-called amide IV-VI bands, assigned compared results density functional theory frequency calculations based on anharmonic vibrational second-order perturbation approach. analysis experimental theoretical data shows that bands diagnostic for geometry moiety backbone. They also strongly blue-shifted upon formation NH⋯O–C hydrogen bonding, which is, example, responsible secondary protein structures. Furthermore, cis be present cyclic peptides. presented work assist assignment similar biologically important systems, either isolated or natural environments.