On the Zwitterionic Nature of Gas-Phase Peptides and Protein Ions

摘要: Determining the total number of charged residues corresponding to a given value net charge for peptides and proteins in gas phase is crucial interpretation mass-spectrometry data, yet it far from being understood. Here we show that novel computational protocol based on force field massive density functional calculations able reproduce experimental facets well investigated systems, such as angiotensin II, bradykinin, tryptophan-cage. The takes into account all possible protomers compatible with state. Our predict low states are zwitterions, because stabilization due intramolecular hydrogen bonding salt-bridges can compensate thermodynamic penalty deriving deprotonation acid residues. In contrast, high may or not be zwitterions internal solvation might energy cost separation.