title: Far infrared spectra of solid state L-serine, L-threonine, L-cysteine, and L-methionine in different protonation states.
abstract: In this study, experimental far infrared measurements of L-serine, L-threonine, L-cysteine, and L-methionine are presented showing the spectra for the 1.0-13.0 pH range. In parallel, solid state DFT calculations were performed on the amino acid zwitterions in the crystalline form. We focused on the lowest frequency far infrared normal modes, which required the most precision and convergence of the calculations. Analysis of the computational results, which included the potential energy distribution of the vibrational modes, permitted a detailed and almost complete assignment of the experimental spectrum. In addition to characteristic signals of the two main acid-base couples, CO2H/CO2(-) and NH3(+)/NH2, specific side chain contributions for these amino acids, including CCO and CCS vibrational modes were analyzed. This study is in line with the growing application of FIR measurements to biomolecules.
authors.affiliation: Laboratoire de Biochimie (CNRS UMR7654), Department of Biology, Ecole Polytechnique, 91128 Palaiseau, France.
authors.forename: Thomas
authors.initials: T
authors.lastname: Gaillard
authors.affiliation: Laboratoire de bio électrochimie et spectroscopie, UMR7140, Chimie de la Matière complexe, Université de Strasbourg, CNRS, 1 rue Blaise Pascal, F-67070 Strasbourg, France.
authors.forename: Aurélien
authors.initials: A
authors.lastname: Trivella
authors.affiliation: Department of Integrative Structural Biology, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Institut National de Santé et de Recherche Médicale (INSERM) U964/Centre National de Recherche Scientifique (CNRS) UMR 7104/Université de Strasbourg, 1 rue Laurent Fries, BP 10142, 67404 Illkirch CEDEX, France.
authors.forename: Roland H
authors.initials: RH
authors.lastname: Stote
authors.affiliation: Laboratoire de bio électrochimie et spectroscopie, UMR7140, Chimie de la Matière complexe, Université de Strasbourg, CNRS, 1 rue Blaise Pascal, F-67070 Strasbourg, France. Electronic address: hellwig@unistra.fr.
authors.forename: Petra
authors.initials: P
authors.lastname: Hellwig
mesh_terms: D003545:Cysteine / Q000737:chemistry*; D008715:Methionine / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D011522:Protons; D012694:Serine / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman; D013912:Threonine / Q000737:chemistry*; D014732:Vibration; D014867:Water / Q000737:chemistry
chemical_list: D011522:Protons; D014867:Water; D013912:Threonine; D012694:Serine; D008715:Methionine; D003545:Cysteine
keywords: Amino acids; DFT; Far infrared spectroscopy