ION-ELECTRON REACTIONS IN VIBRATIONALLY COOLED MALDI FTICR MS

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Because of the interesting new fragmentation patterns available with ECD and EDD, there's a strong interest in implementation of ion-electron reaction in the MALDI FTMS instrument. The Vibrationally Cooled (VC) MALDI built at the NCRR Mass Spectrometry Resource at Boston University School of Medicine is required for cooling of the vibrational motion of the ions and thus increases the abundance of multiply charged species in MALDI. SWIFT-isolated multiply charged ions were irradiated with low energy electrons and electron capture, hydrogen atom loss, and c,a fragment ions (all species that are expected for radical reactions) were detected. Efficiency of fragments is low due to the low abundance of the parent ion, but the fragment ion yield is rougly comparable to electrospray spectra. Thus, we have shown ECD of doubly charged MALDI ions. However, due to the much greater abundance, ion electron reactions were also attempted with the 1+ and 1- ion species. Irradiation of singly charged positive parent ions using electrons of 9-14 eV produced small peaks of further ionized species as well as extensive fragmentation of c,z,b,y,a ions. This new technique is thus named electron induced dissociation, and appears to be very promising for sequencing peptides in high pressure MALDI FTMS. Particularly the new technique will be useful for sequencing peptides with PTM¿s since the fragments have been noted to preserve labile groups such as phosphorylation sites. Electron capture dissociation and electron induced dissociation (EID) techniques were obtained for the first time for High pressure MALDI FTMS. These data were presented at the 52d American Society of Mass Spectrometry in Nashville, TN and are currently being written up for submission as a scientific paper in a peer-reviewed journal.