title: IR spectroscopy of protonated leu-enkephalin and its 18-crown-6 complex embedded in helium droplets.
abstract: Ultracold IR spectra of the protonated five amino acid peptide leu-enkephalin (Tyr-Gly-Gly-Phe-Leu) embedded in superfluid helium droplets have been recorded using a free-electron laser as radiation source. The results show resolved spectra, which are in good agreement with theoretical calculations, as well as with the available gas-phase data indicating that the helium environment does not induce a significant matrix-shift. In addition, the effect of the interaction between the charge and the peptide backbone has been further investigated by complexing protonated leu-enkephalin with one 18-crown-6 molecule. Good agreement between the experimental and theoretical results allow for an assignment of a preferred molecular structure.
authors.affiliation: Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany. helden@fhi-berlin.mpg.de.
authors.forename: Ana Isabel
authors.initials: AI
authors.lastname: González Flórez
authors.forename: Doo-Sik
authors.initials: DS
authors.lastname: Ahn
authors.forename: Sandy
authors.initials: S
authors.lastname: Gewinner
authors.forename: Wieland
authors.initials: W
authors.lastname: Schöllkopf
authors.forename: Gert
authors.initials: G
authors.lastname: von Helden
mesh_terms: D043844:Crown Ethers / Q000737:chemistry*; D004743:Enkephalin, Leucine / Q000737:chemistry*; D006371:Helium / Q000737:chemistry*; D006860:Hydrogen Bonding; D007834:Lasers; D008958:Models, Molecular; D011487:Protein Conformation; D011522:Protons; D012997:Solvents / Q000737:chemistry; D013055:Spectrophotometry, Infrared
chemical_list: D043844:Crown Ethers; D011522:Protons; D012997:Solvents; D006371:Helium; D004743:Enkephalin, Leucine; C015762:18-crown-6