Proton Transfer Reagent Cations for Ion-Ion Charge State Manipulation of High Mass Negatively-charged Analytes in an Electrodynamic Ion Trap

Abstract

This work summarizes the criteria for a useful reagent for ion/ion proton transfer in an electrodynamic ion trap with specific emphasis on proton transfer to high mass multiply-charged analyte ions. A readily available and ionizable weak base of relatively high mass meets the criteria. The protonated form of an extensively fluorinated 10-carbon primary amine (1H,1H,2H,2H-perfluorodecylamine, PFDA) is demonstrated to serve as a useful reagent for proton transfer to negatively-charged proteins and oligonucleotides. The behavior of protonated PFDA is compared with that of protonated 1,8-bis(dimethylamino)naphthalene (proton sponge) with respect to the tendency for proton transfer versus attachment in ion/ion reactions with a common multiply-deprotonated protein and a common multiply-deprotonated oligonucleotide. Protonated PFDA showed a lesser tendency for ion attachment than the proton sponge in all cases. Both reagent cations showed a greater extent of attachment to the oligonucleotide anions. Mild collisional heating was shown to be able to extensively remove adducted PFDA from the oligonucleotide. The ability to generate low z and high m/z analyte product ions from highly charged precursor analyte ions using protonated PDFA is illustrated with anions derived from β-galactosidase, GroEL, and 30S E. coli ribosome particles.