Electron detachment dissociation of peptide di-anions: an electron-hole recombination phenomenon

A novel electron-ion reaction mimicking positron capture is reported for gas-phase polypeptide di-anions. Bombardment of the latter by > 10 eV electrons produced electron detachment followed by backbone dissociation, noticeably cleavage of the N-C-alpha bond. On the other hand, reaction with hydrogen cations resulted in losses of neutral groups but not in backbone cleavage. It is proposed that the N-C-alpha dissociation is due to recombination along the peptide chain of a positive radical charge (hole) with a negative charge. The new reaction is likely to find application in mass spectrometry for primary structure determination of acidic polypeptides. (C) 2001 Elsevier Science B.V. All rights reserved.