Amide vibrations and their conformational dependences in β-peptide.
The characteristics of the amide-A and amide-I modes in a β-homoalanine dipeptide (β-HADP) have been examined as a function of backbone dihedral angles. The harmonic frequencies were obtained using the density functional theory. The anharmonic frequencies and diagonal anharmonicities were obtained by using the Morse potential. Local-mode frequencies and intermode couplings were obtained using the computed normal-mode frequencies and eigenvectors. It was found that the vibrational frequencies for the two types of amide modes are both conformational-dependent. The inter-amide-A and inter-amide-I couplings in the β-peptides were predicted to be generally weaker than those in the α-peptides. Structural bases of the amide-A and amide-I local modes in the β-peptides are discussed.
Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China.
Juan
J
Zhao
Jianping
J
Wang
D000577:Amides / Q000737:chemistry*; D004151:Dipeptides / Q000737:chemistry*; D008968:Molecular Conformation; D011789:Quantum Theory; D014732:Vibration; D015091:beta-Alanine / Q000031:analogs & derivatives / Q000737:chemistry*
D000577:Amides; D004151:Dipeptides; D015091:beta-Alanine