Probing biomolecular fragmentation

Abstract: This thesis deals with fragmentation of complex molecular ions, especially biomolecules, in gas phase collision experiments. The aim is to investigate the relations between energy deposition and fragmentation and to shed light on the mechanisms behind energy and charge transfer processes in collisions involving the building blocks of life. Further, the question how a solvent environment influences the dissociation behavior is elucidated. In the first part of the thesis, results from different collision experiments with biomolecular ions are presented, focusing on electron capture induced dissociation of hydrated nucleotides and small peptides. The investigated processes may be relevant for the understanding of radiation damage and the optimization of sequencing methods used in protein research. Our results clearly demonstrate that effects due to surrounding solvent molecules are substantial. While the dissipation of internal energy by evaporation of the loosely bound solvent molecules may protect the biomolecule, the influence which this environment has on the electronic structure may lead to an enhancement or suppression of certain dissociation channels. The second part of the thesis focuses on recent instrumental developments. Here, the aim was to optimize and complement the techniques used in the experiments above and to have versatile tools available for different kinds of gas phase collision studies involving complex molecular ions. Therefore, we have constructed an electrospray ion source platform for the preparation of intense beams, with options of accumulation and cooling of mass selected ions, allowing for a large variety of experiments. This device is also intended to serve as an ion source for the new storage ring facility DESIREE (DoubleElectroStatic Ion Ring ExpEriment), which is currently under construction at Stockholm University. In these unique storage rings, oppositely charged ions may interact at very low relative velocities in a cryogenically cooled and ultrahigh vacuum environment.