title: VCD Robustness of the Amide-I and Amide-II Vibrational Modes of Small Peptide Models.
abstract: The rotational strengths and the robustness values of amide-I and amide-II vibrational modes of For(AA)n NHMe (where AA is Val, Asn, Asp, or Cys, n = 1-5 for Val and Asn; n = 1 for Asp and Cys) model peptides with α-helix and β-sheet backbone conformations were computed by density functional methods. The robustness results verify empirical rules drawn from experiments and from computed rotational strengths linking amide-I and amide-II patterns in the vibrational circular dichroism (VCD) spectra of peptides with their backbone structures. For peptides with at least three residues (n ≥ 3) these characteristic patterns from coupled amide vibrational modes have robust signatures. For shorter peptide models many vibrational modes are nonrobust, and the robust modes can be dependent on the residues or on their side chain conformations in addition to backbone conformations. These robust VCD bands, however, provide information for the detailed structural analysis of these smaller systems.
authors.affiliation: Laboratory of Molecular Spectroscopy, Institute of Chemistry, Eötvös University, Budapest, Hungary.
authors.forename: Sándor
authors.initials: S
authors.lastname: Góbi
authors.affiliation: Laboratory of Molecular Spectroscopy, Institute of Chemistry, Eötvös University, Budapest, Hungary.
authors.forename: Gábor
authors.identifier: http://orcid.org/0000-0002-1464-7249
authors.initials: G
authors.lastname: Magyarfalvi
authors.affiliation: Laboratory of Molecular Spectroscopy, Institute of Chemistry, Eötvös University, Budapest, Hungary.
authors.forename: György
authors.initials: G
authors.lastname: Tarczay
mesh_terms: D000577:Amides / Q000737:chemistry*; D002942:Circular Dichroism; D008958:Models, Molecular; D010455:Peptides / Q000737:chemistry*; D017433:Protein Structure, Secondary; D012399:Rotation; D013237:Stereoisomerism; D014732:Vibration
chemical_list: D000577:Amides; D010455:Peptides
keywords: VCD robustness; VCD spectroscopy; amide-I and amide-II vibrational modes of peptides; chiroptical spectroscopy; model peptides; peptide structure