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Heather's work involves the use of mass spectrometry to study non-covalently bound clusters. Such clusters provide a unique environment to study molecular behavior. Solvated ions bridge the boundary between solution phase and gas phase chemistry. Non-covalently bound gas phase molecular complexes also exhibit unique reactivity. Without the mediation of solvent, non-covalent and ionic bonds are stronger than in solution, and novel reaction pathways are available to a complex.
Previous work on the Beauchamp's group 7.0T FT-ICR, using a home-built nanospray source, involved ions in solvent clusters. We have examined the effect of solvation on protonation sites in anilinium derivatives and studied the solvation patterns around structure-directing agents, used in zeolite formation. We have also conducted H/D exchange studies on sodiated glycine oligomers, in which a neutral deuterated reagent is introduced into the ion trap and exchanges a deuterium for a hydrogen on the peptide. Using density functional theory calculations, we have found that the rate and extent of exchange depends significantly on the intermediate conformations that the peptide adopts when it is complexed with the exchange reagent. These results indicate that H/D exchange data does not necessarily provide information about the parent ion structure, and such data must be interpreted with caution.
Current work focuses on collisionally activated reactions within gas-phase molecular clusters. While most noncovalently bound gas phase clusters dissociated when collisionally activated, we have found that in some cases, ionic interactions are strong enough to induce reaction in the cluster. We have alkylated triphosphate in this manner. In addition, we have successfully phosphorylated serine, tyrosine, and threonine containing peptides, which are the three amino acids commonly phosphorylated in biological systems and used for cell signalling. Such modification of biomolecules in the gas phase has promise for rapid, high-throughput detection and analysis of complex mixtures of biomolecules.
We are extending our studies to other biological systems.
Heather is also the author of the solutions manual accompanying "Physical Chemisty: A Molecular Approach", by McQuarrie and Simon.
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Beauchamp Research Group |
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