SURFACE-INDUCED DISSOCIATION OF MULTIPLY PROTONATED PROTEINS

A novel surface design compatible with the open cell geometry allows n onglancing angle collisions of selected ions stored in a Fourier trans form mass spectrometer. Dissociation efficiencies of 36%, 22%, and 14% are achieved for gramicidin S, melittin, and carbonic anhydrase (29 k Da), respectively. Ion neutralization by the surface, which is highly competitive for many singly-charged ions, is minimal, and dissociation products of hypervalent neutral species are not detected, Instead, th e spectra are similar to those from collisionally activated and infrar ed multiphoton dissociation; the fragmentation pathways are relatively independent of the method of energy deposition. For carbonic anhydras e, however, the single event excitation inherent to surface-induced di ssociation appears to minimize secondary fragmentation, a critical adv antage for tandem mass spectrometry of such large ions, Electrically f loating the open cell below ground greatly enhances the collection eff iciency.