Low energy CID and action IRMPD provide insights into a minor subpopulation of the gas-phase conformers of triply charged bradykinin

Unique fragmentation of the IMS-resolved conformers of triply charged bradykinin is shown to occur at very low collision energies by quadrupole CID. For the major C conformation of bradykinin, the unique fragmentation appears to result from a subpopulation that has a different average CCS than the dominant C population that has been previously identified as TTC (trans, trans, cis at the three Pro residues). The three major gas-phase isomers exhibit minimal differences in fragmentation at collision energies greater than 12 eV, presumably because the amide bonds of the proline residues isomerize prior to dissociation at these higher energies. The differences in fragmentation observed in the low collision energy regime (