title: Temperature and pressure effects on conformational equilibria of alanine dipeptide in aqueous solution.
abstract: We investigated the temperature and pressure effects on conformational equilibria of N-acetyl-L-alanine-N'-methylamide (AAlaMA) in aqueous solution by Raman spectroscopy. Scattering intensities in the skeletal stretching mode of AAlaMA in aqueous solution were decomposed into some component bands by the spectra analysis. Our results indicate that each component band for AAlaMA adopts not only the P(II) and alpha(R) conformations but also the C(7eq) conformation. From temperature and pressure dependencies of the band intensities, we determined the enthalpy differences and the volume differences between the conformers. The C(7eq) conformer is enthalpically most stable due to the intramolecular hydrogen bond. The partial molar volume of the C(7eq) conformer is the smallest through the solvent-exclusion effect rather than the solute-solvent electrostatic interaction effect.
authors.affiliation: Department of Applied Chemistry, Ritsumeikan University, Kusatsu, Shiga, 525-8577, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Takekiyo
authors.forename: Takashi
authors.initials: T
authors.lastname: Imai
authors.forename: Minoru
authors.initials: M
authors.lastname: Kato
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Taniguchi
mesh_terms: D000409:Alanine / Q000031:analogs & derivatives* / Q000737:chemistry*; D004151:Dipeptides / Q000737:chemistry; D011312:Pressure; D011487:Protein Conformation; D013059:Spectrum Analysis, Raman; D013696:Temperature; D014867:Water / Q000737:chemistry
chemical_list: D004151:Dipeptides; D014867:Water; C024314:N-acetylalanyl-N-methylamide; D000409:Alanine