Professor Evan Williams of the U of Cal Berkeley is supported by the Analytical and Surface Chemistry Program to study hydration of amino acids in the gas phase using new methods in mass spectrometry. The research is in two areas, both involving ion formation by electrospray ionization (ESI) and mass analysis by Fourier/transform ion cyclotron resonance mass spectrometry (FT/ICR MS). The first area focuses on the structures of amino acids that are cationized by added metal ions and also contain a varying number of water molecules. The structures of these systems are investigated by blackbody infrared radiative dissociation (BIRD) and by infrared (IR) spectroscopy. The main goal of these studies is to determine how many water molecules are needed for the amino acids to change from a nonzwitterion structure (most common in the gas phase) to a zwitterion structure (prevalent in aqueous solution). The PI has already conducted BIRD studies on solvated ions of lithiated and sodiated valine, which showed that at least three water molecules are necessary for the zwitterion structure to become more stable in the gas phase (as it is in bulk aqueous solution). The renewed research project extends such studies to more complex amino acids (proline, glutamine, lysine), whose solvated ions will additionally be investigated by IR spectroscopy using a laser. The second area of research focuses on the development of a new method for the dissociation of large ions, which cannot be dissociated using BIRD. Heated filaments are used to provide the higher energies needed to dissociate larger systems. Taken together, these experiments should provide a better understanding of how heteroatoms in amino acid side chains and water molecules solvate charge in proteinaceous environments. They also should provide information about how water and the dehydration process in ESI affects ion structure.
Mass spectrometry plays an ever increasing role in analytical science, and the proposed research will educate and train scientists in this growing field, which is extensively applied in biology, medicine, and biotechnology research. In addition, this fundamental research on the building blocks of proteins will enable researchers to sequence proteins more rapidly and accurately.
