Grant: Research Tools and Instruments - Category 1 (<$150,000)

The association and dissociation of noncovalent protein complexes are critical events in many biological processes. The structure and stability of these complexes are determined by the concerted action of many forces between binding partners and from the displacement and reorganization of water molecules associated with the solvent shell of the binding partners. An understanding of these forces and the structures they lead to is of fundamental and applied interest. A key challenge to achieving a more complete description of the molecular recognition processes is the separation of the solvent effects from the intrinsic solute-solute interactions. Our laboratory is utilizing gas phase measurements to tackle this significant and challenging problem. Gas phase studies of desolvated protein complexes afford an opportunity to directly probe the intrinsic intermolecular interactions and, indirectly, the role of solvent in molecular recognition. Many specific protein complexes are readily transferred from aqueous solution to the gas phase using electrospray ionization (ESI). Once in the gas phase, the desolvated ions can be interrogated using a variety of mass spectrometry (MS)-based techniques. The goal of this proposal is to secure funds to acquire a high power continuous wave (cw) OPO laser to carry out infrared multiphotodissociation (IRMPD) spectroscopy measurements on gas phase ions of biological complexes. In IRMPD spectroscopy, tunable IR radiation is used to dissociate isolated gaseous ions and the extent of fragmentation is measured as a function of radiation wavelength. Typically, these measurements are carried out using Fourier-transform ion cyclotron resonance MS, wherein the ions of interest are isolated and trapped at ultra-high vacuum within the ion cell. We will use the IRMPD spectroscopy technique to investigate the higher order structure of the gas phase ions of a variety of noncovalent biological complexes to assess the influence of desovlation on structure and stability. We will also apply this technique to explore the nature of discrete lipid interactions with membrane protein complexes with the goal of establishing how lipid structure influences membrane protein structure and function.