title: IR-induced conformational isomerization of a helical peptide in a cold ion trap.
abstract: In this work, we use laser-induced population transfer techniques to study the conformational isomerization of a helical peptide, Ac-Phe-(Ala)5-LysH(+), in a cold ion trap. In one scheme, called IR-UV hole-filling spectroscopy, a single conformation is selectively excited with an IR pump laser via a distinct NH stretch vibration. After giving the vibrationally excited ions sufficient time to isomerize and re-cool in the trap, the new conformational redistribution is detected by UV photofragment spectroscopy. While we clearly observe a redistribution of the conformer populations due to isomerization, only those conformations that initially have population participate in this redistribution-we do not form conformers that were not initially present in the trap. In a second scheme, called IR-induced population transfer spectroscopy, we determine the fractional populations of the four stable conformations of Ac-Phe-(Ala)5-LysH(+) by scanning the IR laser while selectively detecting a specific conformation using UV photofragment spectroscopy.
authors.affiliation: Laboratoire de Chimie Physique Moléculaire, Ecole Polytechnique Fédérale de Lausanne, EPFL SB ISIC LCPM, Station 6, CH-1015 Lausanne, Switzerland.
authors.forename: Caroline
authors.initials: C
authors.lastname: Seaiby
authors.affiliation: Laboratoire de Chimie Physique Moléculaire, Ecole Polytechnique Fédérale de Lausanne, EPFL SB ISIC LCPM, Station 6, CH-1015 Lausanne, Switzerland.
authors.forename: Aleksandra V
authors.initials: AV
authors.lastname: Zabuga
authors.affiliation: Laboratoire de Chimie Physique Moléculaire, Ecole Polytechnique Fédérale de Lausanne, EPFL SB ISIC LCPM, Station 6, CH-1015 Lausanne, Switzerland.
authors.forename: Annette
authors.initials: A
authors.lastname: Svendsen
authors.affiliation: Laboratoire de Chimie Physique Moléculaire, Ecole Polytechnique Fédérale de Lausanne, EPFL SB ISIC LCPM, Station 6, CH-1015 Lausanne, Switzerland.
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Rizzo
mesh_terms: D007259:Infrared Rays; D007477:Ions / Q000737:chemistry; D010455:Peptides / Q000737:chemistry* / Q000528:radiation effects*; D011487:Protein Conformation / Q000528:radiation effects; D013056:Spectrophotometry, Ultraviolet; D013237:Stereoisomerism
chemical_list: D007477:Ions; D010455:Peptides