Infrared spectroscopic studies of ionic and neutral biomolecules and their solvated complexes

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The proposed research is focused on the structure elucidation of both neutral and ionic molecules and complexes, especially those which can participate in weak intramolecular bonding.  In their natural state, proteins and other biological molecules are multiply protonated. They can also be bound to metal cations and this is often required for biological activity.  The proposed research will provide insight into the salient weak intramolecular interactions which are present in biologically relevant molecules by studying the infrared spectra of these species isolated in rare-gas matrices at cryogenic temperatures where they can be stored and studied indefinately.  The degree of interaction with another portion of the molecule (intramolecular bonding) can be studied by the shifts in  position of the infrared absorption.  For example, when glycine is bound to a sodium cation, one of the isomers is expected to exhibit strong intramolecular hydrogen bonding between a carbonyl oxygen and an amino hydrogen.  The N-H stretch is seen to red-shift by some 800 wavenumbers from that of a normal N-H stretch.   The effect of sequentially solvating (with 1, 2 or more solvent molecules such as water) biologically interesting ions and neutrals will be studied in order to bridge the gap between the intrinsic properties of the gas-phase molecule and those of the molecule in its natural, solvated state.  With the proposed experiments we will be able to assess the structural changes which occur at each stage solvation. This research is expected to play an important role in determining the structure, and the effect of solvent on the structure, of life's building blocks.  This will lead to a more detailed, fundamental understanding of the role of the biomolecule and the role of solvent in biological activity.  Furthermore, this research will provide spectral signatures for biological ions and neutrals which can eventually aid in the use of infrared spectroscopy for diagnostic purposes.