Hannover 2010 – wissenschaftliches Programm

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MS: Fachverband Massenspektrometrie

MS 2: Speicherringe und neue Entwicklungen

MS 2.2: Hauptvortrag

Montag, 8. März 2010, 17:00–17:30, F 428

Photodissociation of dipeptide cations in an electrostatic ion storage ring — •Steen Brøndsted Nielsen — Department of Physics and Astronomy, Aarhus University

In photobiology, the aromatic amino acids phenylalanine, tyrosine, and tryptophan are highly important spectroscopic probes for protein conformations and dynamics. They act as markers because of the fact that their photophysics is highly dependent on the chemical environment. To have a proper reference for the intrinsic properties, it is necessary to establish the electronic properties of amino acids without any perturbations from solvent molecules, counter ions, or other amino acids. This requires gas phase experiments on individual molecules. In Aarhus we have developed a setup to record gas-phase absorption spectra of biomolecular ions. It combines an electrospray ion source, a multipole ion trap for pre-storage, an electrostatic ion storage ring, and pulsed tuneable lasers. The technique relies on the measurement of delayed dissociation of photoexcited ions (action spectroscopy). In this talk I will present some of our recent results on dipeptide cations and demonstrate how the electronic structure is linked to peptide conformation. Tagging the positively charged ammonium group with crown ether prevents internal ionic hydrogen bonding and leads to open structures. This influences dissociation lifetimes and channels.