title: Quantum-classical description of the amide I vibrational spectrum of trialanine.
abstract: A quantum-classical description of the amide I vibrational spectrum of trialanine cation in D2O is given that combines (i) a classical molecular dynamics simulation of the conformational distribution of the system, (ii) comprehensive density functional theory calculations of the conformation-dependent and solvent-induced frequency fluctuations, and (iii) a semiclassical description of the vibrational line shapes which includes nonadiabatic transitions between vibrational eigenstates. Various assumptions that are usually employed in the calculation of condensed-phase vibrational spectra are tested, including the adiabatic, the Franck-Condon, and the second-order cumulant approximations, respectively. All three parts of the theoretical formulation are shown to have a significant impact on the simulated spectrum, suggesting that the interpretation of peptide amide I spectra may require substantial theoretical support.
authors.affiliation: Institute of Physical and Theoretical Chemistry, J. W. Goethe University, Max-von-Laue-Strasse 7, D-60438 Frankfurt, Germany.
authors.forename: Roman D
authors.initials: RD
authors.lastname: Gorbunov
authors.forename: Phuong H
authors.initials: PH
authors.lastname: Nguyen
authors.forename: Maja
authors.initials: M
authors.lastname: Kobus
authors.forename: Gerhard
authors.initials: G
authors.lastname: Stock
mesh_terms: D000577:Amides / Q000737:chemistry*; D003198:Computer Simulation; D009842:Oligopeptides / Q000737:chemistry*; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011789:Quantum Theory; D013057:Spectrum Analysis
chemical_list: D000577:Amides; D009842:Oligopeptides; C039944:alanyl-alanyl-alanine