Collision-induced dissociation for mass spectrometric analysis of biopolymers: high-resolution Fourier transform ion cyclotron resonance MS4.

Efficient collision-induced dissociation multistage tandem high-resolution mass spectrometry of peptide ions is demonstrated for the first time. Specifically, four-stage Fourier transform ion cyclotron resonance collision-induced dissociation tandem-in-time MS4 is demonstrated for bradykinin quasimolecular ions, MH+, produced by matrix-assisted laser desorption/ionization. We combine off-resonant excitation and ion axialization to improve the efficiency of parent ion dissociation and product ion collection and detection at every MS stage. We observe successive loss of water/ammonia from the C-terminus to leave an (MH-NH3/H2O)+ ion in the second stage, followed by successive losses of the next two amino acids, arginine and phenylalanine. High mass resolving power is achieved throughout all four MS stages, in an experiment that consumes approximately 10 pmol of peptide and takes only approximately 5 min. We project that it should be possible to automate this experiment for high-speed sequencing of biopolymers.