The influence of peptide structure on fragmentation pathways

PhD ceremony: Ms. S. Bari, 11.00 uur, Academiegebouw, Broerstraat 5, Groningen

Title: The influence of peptide structure on fragmentation pathways

Promotor(s): prof. R. Hoekstra

Faculty: Mathematics and Natural Sciences

The current increasing social and corporate interest in proton- and heavy ion-therapy of malignant tumours now results in the construction of first particle treatment centres. The chemical and biological aspects of biological radiation damage have been studied in great detail. However, little is known about biological radiation action on the molecular level. Experiments with small biomolecules in the gas phase have the advantage of studying ionization and fragmentation dynamics in finite systems but are less realistic radiation damage models. To be able to investigate more complex biomolecular systems, such as large proteins, we have developed a new apparatus in which a home built electrospray source is interfaced with a low energy (keV) ion beamline or a VUV photon beamline.

Being a pioneering study, this thesis aims at paving the way for studies on radiation upon complex biomolecule by an in depth investigation of ion- and photo-induced fragmentation of the relatively small model-peptide leucine enkephalin. Additionally, systematic fragmentation studies on different amino acids were performed. The central theme of the performed studies is the influence of the molecular structure on the fragmentation pathways upon ion or photon impact.

An explicit dependence of the fragmentation of leucine-enkephalin on the projectile parameters is observed and the distinguishing feature of amino acids, the sidechain, dominates the peptide spectra.