However, the question of ionization pathways, particularly proton transfer between FA clusters, and its interaction with water remains unresolved and recently there have been several experimental and theoretical studies which have attempted to shed light on this problem. Electron ionization of FA clusters embedded in helium nanodroplets showed both anionic and protonated FA clusters. The authors discussed their results in the context of the stability of the ions in the cold environment of helium nanodroplets and suggested that mass spectral distributions could have a very sensitive dependence on source and ionization conditions. It was revealed that beyond protonated FA clusters, there are other fragmentation channels which could lead to the formation of new moieties complexed with water.