Gas-phase formation of large neutral alkaline-earth metal tryptophan complexes

We report on the first observation of isolated large neutral metal amino acid complexes such as Trp(n)Me(k), with Me=Ca, Ba, Sr, cluster combinations covering n=1...33, k=0..2 and masses beyond 6500 u. The cluster beam is generated using UV laser desorption from a mixed powder of alkaline-earth metal salts and tryptophan inside a cluster mixing channel. The particles are detected using VUV photoionization followed by time-of-flight mass spectroscopy. The enhanced stability of metal amino acid clusters over pure amino acid clusters is substantiated in molecular dynamics simulations by determining the gain in binding energy related to the inclusion of the metal atoms.

Gas phase sorting of fullerenes, polypeptides and carbon nanotubes

We discuss the Stark deflectometry of micro-modulated molecular beams for the enrichment of biomolecular isomers as well as single-wall carbon nanotubes, and we demonstrate the working principle of this idea with fullerenes. The sorting is based on the species-dependent susceptibility-to-mass ratio χ/m. The device is compatible with a high molecular throughput, and the spatial micro-modulation of the beam permits one to obtain a fine spatial resolution and a high sorting sensitivity.