Bioanalytical Mass Spectrometry/Peptide and Protein Sequencing/ Ion-Surface Collisions for Surface Characterization of Organic Thin Films/Biodefense/Mosquito Proteomics and Metabolomics

Research in the Wysocki group is separated into three broad areas: (1) determination of peptide dissociation mechanisms as a means for improving programs used for automated sequencing of peptides and proteins, (2) surface characterization of organic thin films, and (3) implementation of surface-induced dissociation onto commercial time-of-flight instruments. The research involves collisions of selected reactive and non-reactive ions with well-ordered surfaces (e.g., self-assembled monolayer films of alkanethiols on gold;Langmuir-Blodgett films). The nature of the surface, the type of projectile ion, and the collision energy are the major experimental variables that are explored.

Research in progress on biomolecules is addressing several different questions involving singly and multiply protonated peptides. All of the related projects are designed to increase the current understanding of the hydrogen bonding interactions and fragmentation patterns of activated protonated peptides. The long range goals of this work are to provide additional "rules" that can be used to enhance automated primary sequencing of peptides and proteins by tandem mass spectrometry and, ultimately, to relate information on gas-phase fragmentation patterns and energetics of dissociation to peptide and protein conformation.

Major aims of our surface characterization research are to determine whether the ion/surface chemistry that is detected when low-energy (eV), gas-phase polyatomic ions collide with a well-ordered surface can be used to quantitate the composition of mixed-composition films and to characterize electron transfer through organic thin films in the absence of solvent. Model compounds ("probe ions") are used to define the reactivity of projectile ions with various functional groups at the surface. Projectile ions used include small, odd-spin species such as distonic radical cations and their conventional counterparts; small aromatic compounds with electron-donating and electron-withdrawing groups; large, refractory molecules such as buckminsterfullerene (C₆₀). These different categories of reagents provide distinct types of information on the mechanisms of electron and atom transfer from surfaces to probe ions and on the analytical utility of ion/surface reactions for surface characterization.

A third area of research is the development of improved mass spectrometers for structural characterization of large molecules. Instruments that allow low-energy ion-surface collisions are not available commercially. Commercial MALDI-TOF(matrix-assisted laser desorption time-of- flight) instruments do not have an efficient means of fragmenting the ions. We have recently shown that surface-induced dissociation can be accomplished with good resolution in a sector/time-of-flight instrument and will extend this work to a commercial MALDI system.

• C.M. Jones, R.L Beardsley, A.S. Galhena, S. Dagan, G.L. Cheng, V.H. Wysocki, "Symmetrical Gas-Phase Dissociation of Noncovalent Protein Complexes via Surface Collisions" Journal of the American Chemical Society , 2006, 128(47), 15044-15045.

• G.L. Cheng, M.A. Cusanovich, V. H. Wysocki, " Properties of the Dark and Signaling States of Photoactive Yellow Protein Probed by Solution Phase Hydrogen/Deuterium Exchange and Mass Spectrometry" Biochemistry., 2006, 45(39), 11744-11751.

• V.J. P. Scaraffia, Q. Zhang, V.H. Wysocki, J. Isoe, M. A. Wells "Analysis of whole body ammonia metabolism in Aedes aegypti using [15N]-labeled compounds and mass spectrometry" Insect Biochemistry and Molecular Biology., 2006, 36(36), 614-622.

• K.A. Herrmann, K. Kuppannan, V.H. Wysocki, Fragmentation of doubly-protonated peptide ion populations labeled by H/D exchange with CD3OD International Journal of Mass Spectrometry ., 2006, 249, 93-105.

• Y. Huang, J. M. Triscari, G.C. Tseng, L. Pasa-Tolic, M. S. Lipton, R.D. Smith, V. H. Wysocki "Statistical Characterization of the Charge State and Residue Dependence of Low-Energy CID Peptide Dissociation Patterns" Analytical Chemistry ., 2005, 77,(18), 5800-5813.

• V. H. Wysocki, K. A. Resing, Q. Zhang, G. Cheng, "Mass Spectrometry of Peptides and Proteins" Methods., 2005, 35 (March), 211-222.