November 2006 Meeting Announcement, Delaware Valley Mass Spectrometry Discussion Group
- Topic: "Mass Spectrometry Methods for the Characterization of Proteins and Noncovalently-Bound Protein Complexes
- Speaker: : Joseph A. Loo, Department of Chemistry and Biochemistry,
University of California Los Angeles
- Date: Monday, November 13, 2006. 6:30 PM
- Time: Social Hour: 6:30 PM.
Talk: 7:30 PM.
Please RSVP to Christopher Petucci PETUCCC@wyeth.com by Thursday November 9th.
- Place: Department of Chemistry, Villanova University (Room 154, Mendel Hall)
The development of electrospray ionization (ESI) for the mass spectrometry measurement of large biomolecules has opened new applications that have the potential to impact biomedical research. Our laboratory has been active in applying ESI-MS for the elucidation of protein structure and also for the characterization of protein-ligand complexes. The noncovalent binding of protein-ligand complexes is well defined in solution. We have used ESI-MS and MS/MS to probe the character of small molecule ligands and metal ion binding to protein targets, even for complexes with solution binding constants in the millimolar range. For ligands with a significant electrostatic component, the stability and dissociation behavior do not reflect their solution affinities, as electrostatic interactions are strengthened in the gas phase and are difficult to disrupt. Using top-down electron capture dissociation (ECD) and high resolution Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry, we demonstrate a strategy to determine the sites of ligand binding onto protein targets. Although ECD has demonstrated to be uniquely capable to determine amino acid sequence for large, intact proteins directly, ECD also does not affect noncovalent interactions, i.e., noncovalent bonds are not disrupted. As a result, protein-ligand interactions are retained by top-down ECD-MS. Methods based on ion mobility analyzers coupled with ESI can extend the size range of proteins and protein complexes to beyond the megaDalton regime. Potentially, ESI-ion mobility can play a role in the measurement of aggregation processes that can occur for a number of proteins.
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