Hannover 2010 – scientific programme

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MO: Fachverband Molekülphysik

MO 17: Biomolecules

MO 17.9: Talk

Wednesday, March 10, 2010, 18:30–18:45, F 142

Isolation of charged (bio)molecules in liquid helium nanodroplets — •Frauke Bierau, Peter Kupser, Gerard Meijer, and Gert von Helden — Fritz-Haber-Institut, D-14195 Berlin, Germany

Superfluid helium droplets provide an isothermal ultracold environment for embedded molecules and are ideal matrices for optical spectroscopy [1].

We set up an experiment, which provides a facility to perform (vibrational) spectroscopy on ultracold mass-selected biomolecules in helium droplets. Proteins or peptides are brought into the gas phase via electrospray ionization (ESI), are stored in a linear ion trap and picked up by helium droplets.

We have seen that molecular ions as big as Cytochrome C (≃12kDa) can be incorporated in He droplets and are detectable as an electrical current on a copper plate. The He droplet masses were determined by electrostatic deflection in an electrical field between two plates, whereupon the deflection angle was measured as a function of the charge state of an embedded Cytochrome C ion. It turned out that the He droplets are real massive and composed of more than 10¹⁰ He atoms per droplet under the initial expansion source parameters [2] of 30 bar and 8K. After being picked up, the cold dopant molecules can be irradiated by a counter-propagating laser beam, and spectroscopic experiments can be performed. [1] J. P. Toennies, A. F. Vilesov, Angew. Chem. Int. Ed. 2004, 43, 2622, [2] H. Buchenau et al., J. Chem. Phys. 1990, 92, 6875