| University of Alberta |
 |
Chemistry at U of A |
Our research program focuses on the development and application of mass spectrometry-based echniques, implemented with a 9.4 tesla Fourier-transform ion cyclotron resonance mass spectrometer (FT-ICR MS) equipped with a nanoflow electrospray (nanoES) source, to study the composition, topology and physicochemical properties of protein complexes in the gas and condensed phases.
One component of our research program involves the use of time-resolved ion-molecule and ion-dissociation reactions to study the structure and reactivity of gaseous protein assemblies and protein-ligand complexes. These studies are of considerable fundamental importance, providing insight into the intrinsic properties of proteins and protein complexes in the absence of solvent, and are critical to the evolution of mass spectrometry as a powerful tool for proteomics. A second area of research deals with the development of novel strategies to map protein interaction sites and quantify association free energies in the aqueous phase. Some of the specific research projects in our laboratory are described below. |
| Structural Characterization of Protein Assemblies |
We are using time-resolved dissociation
experiments to dissect gaseous protein
assemblies to obtain information on
composition, quaternary structure and
binding energetics. While the concept is
straightforward, implementation is hindered
by the limited fragmentation observed for
the assemblies and an incomplete
understanding of the dissociation
mechanisms. Using the blackbody infrared
radiative dissociation (BIRD) technique, we
are investigating the dissociation pathways,
kinetics and energetics of assemblies in the
gas phase. These studies provide new insight
into the dissociation mechanism and the
influence of charge and higher order
structure thereon and suggest new strategies
to increase the structural information
available from MS. |
| Mapping Intrinsic Protein-Ligand Interactions |
Our laboratory is mapping the intermolecular
interactions present in gaseous protein-ligand
complexes. Using a functional group
replacement strategy and a thermal
activation technique, the nature and
strength of the dominant intermolecular
interactions in gaseous
protein-oligosaccharide complexes are being
determined. Comparison of the gas phase data
with solution thermochemistry and crystal
structures provides new insights into the
structural and energetic role of solvent in
association. The protein-ligand interaction
energies determined in this work are also
important for the development of accurate
force fields for improved molecular modeling
of biomolecules and their complexes. |
| Binding Affinity and Stoichiometry of Protein-Ligand Complexes |
Another component of our research program
deals with the application of nanoES-FT-ICR
MS to evaluate the affinity and
stoichiometry of weakly-binding protein-ligand
complexes in solution. Quantification of the
solution composition based on the gas-phase
ion abundance is often hindered by spectral
artifacts originating from the nanoES
process (e.g. non-specific binding) and
gas-phase processes (e.g.decomposition). We
are exploring aspects of the nanoES process
as well as the relative stability of
specific and non-specific protein-ligand
complexes to establish experimental
conditions that minimize such artifacts. |