| AVS 54th International Symposium | |
| Plasma Science and Technology | Thursday Sessions |
| Session PS2+BI-ThA |
| Session: | Plasmas in Bioscience |
| Presenter: | J. Laskin, Pacific Northwest National Laboratory |
| Authors: | J. Laskin, Pacific Northwest National Laboratory O. Hadjar, Pacific Northwest National Laboratory P. Wang, Pacific Northwest National Laboratory Z. Yang, Pacific Northwest National Laboratory |
| Correspondent: | Click to Email |
Interaction of ions with surfaces is an area of active research in surface science relevant to a broad range of other scientific disciplines such as materials science, mass spectrometry, imaging and spectroscopy. Our research is focused on fundamental understanding of interaction of hyperthermal (1-100 eV) peptide, protein and polymer ions with organic surfaces under ultrahigh vacuum conditions. Two major processes are dominant for this range of collision energies: reactive and non-reactive scattering of ions and ion loss on the surface as a result of neutralization or soft-landing (SL) of projectile ions. Scattering and deposition of large ions following collisions with SAM surfaces was studied using a unique Fourier transform ion cyclotron resonance mass spectrometer developed in our laboratory. Ion activation by collisions with surfaces is rather poorly characterized from a fundamentals perspective. We explored the effect of the physical and chemical properties of SAM surfaces on the energy transfer in collisions. Our studies demonstrated that energy distribution functions are well-represented by Maxwell-Boltzmann distributions indicating fast thermalization of ions by collisions. A notable discovery was a sharp transition between slow unimolecular decay of large ions at low collision energies and near-instantaneous decomposition (shattering) in higher energy surface collisions. Shattering of ions on surfaces opens up a variety of fragmentation pathways for large complex ions that are not accessible to conventional ion activation techniques. We have conducted first systematic study of several factors that affect SL of peptide ions on SAM surfaces. Deposition of peptide ions of different composition and charge state on SAM surfaces was followed by in situ and ex situ SIMS analysis. Peptide ions are attractive model systems that provide important insights on the behavior of soft landed proteins. We were able to measure for the first time the binding energy between peptide ions and hydrophobic SAM surfaces. We also demonstrated very strong binding of peptide ions to hydrophilic surfaces and covalent linking of peptides to reactive SAMs. Fundamental principles derived from such studies of interaction of protonated peptides with hydrophobic or hydrophilic surfaces are relevant to the understanding of the transport of biomolecules through membranes in living organisms and provides a clear pathway for highly-selective preparation of biological surfaces.