ION ION PROTON-TRANSFER REACTIONS FOR PROTEIN MIXTURE ANALYSIS/

Ion/ion proton transfer reactions are shown to tie an effective means to facilitate the resolution of ions in electrospray mass spectrometry that differ in mass and charge but are similar in mass-to-charge rati o, Examples are shown in which a minor contaminant protein in a ribonu clease B solution is clearly apparent after ion/ion proton transfer bu t not in the conventional electrospray mass spectrum, A further exampl e involving a mixture of bovine serum albumin and bovine transferrin a lso showed the identification of a previously unnoticed ''contaminant' ' polymer, The latter mixture also illustrated important issues in the use of the quadrupole ion trap as a reaction vessel and mass analyzer for high mass-to-charge ratio ions, The results suggest that the use of ion trap operating parameters specifically tailored for storage, ej ection, detection, and mass-to-charge analysis of high mass-to-charge ratio ions can have attractive analytical figures of merit for determi ning mixtures of relatively high-mass proteins and, by extension, othe r types of high-mass biopolymers.