Amide I Vibrational Properties Affected by Hydrogen Bonding Out-of-Plane of the Peptide Group.
The amide I vibrational properties of a peptide-water complex in various intermolecular configurations are analyzed theoretically to see whether a water molecule with a weak out-of-plane hydrogen bond really induces a large low-frequency shift. It is shown that the frequency shift strongly depends on the C═O···H angle, with a larger low-frequency shift as the C═O···H becomes more bent, suggesting that the so-called hydrated helix with a rather low amide I frequency has an additional water molecule located out-of-plane of the peptide group as compared with a typical α-helix. The infrared intensity also depends on the angular position of water. A new model parameter set (that can be combined with molecular dynamics) is developed for a more correct representation of the hydration-induced frequency shift. The question regarding the scalar and vectorial nature of the molecular properties related to the frequency shift is also discussed.
Department of Chemistry, Faculty of Education, and Department of Optoelectronics and Nanostructure Science, Graduate School of Science and Technology, Shizuoka University, 836 Ohya, Shizuoka 422-8529, Japan.
Hajime
H
Torii
D000577:Amides / Q000737:chemistry*; D006860:Hydrogen Bonding; D008962:Models, Theoretical; D010455:Peptides / Q000737:chemistry*; D014732:Vibration
D000577:Amides; D010455:Peptides
electrostatic interaction; hydrogen bond; peptide; vibrational mode