  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$\approx$12 000 amu protein Cytochrome C in
selected charge states. The sizes of the ion-doped droplets are determined via
electrostatic deflection. Under the experimental conditions employed, the
observed droplet sizes are very large and range, dependent on the incorporated
ion, from 10$^{10}$ helium atoms for protonated Phenylalanine to 10$^{12}$
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.
