Electronic Excitation Gives Informative Fragmentation of Polypeptide Cations and Anions

A Fourier transform mass spectrometer is a versatile instrument with a range of available fragmentation techniques. Comparison of polypeptide fragmentation patterns revealed that the techniques involving electronic excitation, such as hot-electron-capture dissociation (HECD) and electron-detachment dissociation (EDD), are even more informative than vibrational excitation (VE) techniques such as collisional activation. For dications of the peptide KIMHASELMANN, 11 eV HECD cleaved all inter-residue links in at least two places, with up to five fragments characterizing each link. For dianions of the same molecule, VE produced only one backbone cleavage whereas EDD gave ten, including five internal cleavage fragments. This is consistent with the general postulate that homogeneous electronic excitation yields more types of cleavage than near-equilibrium processes such as VE.