Kenneth B. Tomer
Mass Spectrometry Group
Kenneth B. Tomer, Ph.D.
Principal Investigator - Retired
Research interests are concentrated in two areas. The first is the application of mass spectrometric techniques to structural biology. We have developed a combination of proteolytic protection assays combined with matrix-assisted laser desorption ionization (MALDI) mass spectrometry for the determination of the conformational epitopes on antigens to monoclonal antibodies. These techniques are currently being applied to the determination of epitopes on the HIV core protein p24 involved in recognition by monoclonal antibodies (MAbs) and to the envelope protein gp120 involved in the initial steps of cellular infection by the HIV virus. We have used this approach to determine functional epitopes on HIV proteins recognized by both in vitro and in vivo neutralizing antibodies. Additional tertiary structural information about conformational and discontinuous epitopes has been probed by selective modification of surface-accessible residues with analysis by mass spectrometry.
The combination of these approaches, along with chemical crosslinking, is now being used to characterize the interaction surfaces in protein:protein complexes. The second area of interest is the development of separation techniques combined with mass spectrometry for the analysis of complex mixtures of low levels of biomolecules. The separation techniques include affinity chromatography, capillary electrophoresis, capillary LC and microdialysis. We have shown that affinity-bound analytes at the femtomole level can be directly analyzed by MALDI/MS without further isolation steps. We have developed interfaces for capillary electrophoresis, capillary LC, and in vivo microdialysis combined with soft ionization techniques. High separation efficiencies and excellent detection limits make these techniques ideally suited for the analysis of complex mixtures. We also have a strong interest in developing mass spectrometry-based methods for the determination of posttranslational modifications, especially phosphorylation and glycosylation.