The Atlanta Area Chemical Physics (AACP) seminar series presents Dr. Jean Futrell, Pacific Northwest National Laboratory

Mass Spectrometry Studies of Collisions of Peptide Ions with Surfaces

Current fundamental and applied research in mass spectrometry emphasizes complex molecular ions, particularly ionized biomolecules. For such ions fragmentation is severely constrained by two factors. Energy transfer in collisions decreases in inverse proportion to ion mass and the dramatic increase in density of states with complexity of the ion decreases the rate of dissociation of energized ions by several orders of magnitude. Consequently typical excitation schemes include multiple gas phase collisions (SORI) or multiple photon absorption to dissociate complex ions in the time frame sampled by mass spectrometers. An attractive alternative is ion surface collisions with special semiconductor surfaces - specifically, with self-assembled monolayers on a metal substrate. In this method a single sub-picosecond collision is sufficient to excite complex ions to arbitrarily high energies. Collision energy and time-resolved studies with RRKM-modeling of their dissociation behavior enables deduction of detailed kinetic parameters for low energy decomposition pathways. At higher energy, and for more complex peptides, transition to a shattering mechanism opens a variety of dissociation channels that are not accessible by multiple-collision or multi-photon excitation. Changing the nature of the self-assembled monolayer surface significantly alters energy transfer efficiency and the efficiency of capture of intact biomolecular ions on the surface. Recent work has focused on the fate of peptide ions captured on the surface, using real-time SIMS to interrogate surface composition before, during, and after ion deposition.

For more information contact Dr. Christine Payne (404-385-3125).