In addition to photon activation methods, our lab has investigated the use of collisional activation with a inert backround gas. Trapped ions are accelerated with the ion cell, producing energetic collisions. Droplets are formed when a solution is feed through a thin capillary which is kept at a high voltage. Under the proper conditions, hydrated metal and peptide ions can be formed. By measuring the dissociation energies of successive water losses, information about the structure of these ions can be inferred.
Electrostatic interactions are important in determining the structure and function of biomolecules.
Amino acids exist as zwitterions in solution under a wide range of conditions, but in the gas phase, the most stable structure is neutral. The zwitterionic structure can be stabilized by the electric field of a nearby counterion and through interaction with polar solvent molecules. An improved understanding of these effects is crucial to understanding and predicting solution-phase properties. Gas phase amino acid complexes were formed using electrospray ionization. Structures of these amino acid complexes were determined by selecting many low energy structures generated using molecular mechanics and performing energy minimization calculations using density functional theory.