An experimental approach is presented that allows for the incorporation of large mass/charge selected ions in liquid helium droplets. It is demonstrated that droplets can be efficiently doped with a mass/charge selected amino acid as well as with the much bigger m≈12 000 amu protein Cytochrome C in selected charge states. The sizes of the ion-doped droplets are determined via electrostatic deflection. Under the experimental conditions employed, the observed droplet sizes are very large and range, dependent on the incorporated ion, from 1010 helium atoms for protonated Phenylalanine to 1012 helium atoms for Cytochrome C. As a possible explanation, a simple model based on the size- and internal energy-dependence of the pickup efficiency is given.
@article{arxiv.1008.3816,
title = {Catching proteins in liquid helium droplets},
author = {Frauke Bierau and Peter Kupser and Gerard Meijer and Gert von Helden},
journal= {arXiv preprint arXiv:1008.3816},
year = {2010}
}