Ionization-induced fragmentation dynamics of isolated complex biomolecules

Intense research on biological radiation damage has been performed since the end of the 19th century, starting almost immediately after the discovery of ionizing radiation. Conclusions from radiobiological in vivo and in vitro experiments can often be employed in a straightforward way to answer questions from radiotherapy or radiation protection. However, from such studies it remains difficult, if not impossible, to obtain detailed information on the molecular mechanisms underlying biological radiation damage.

About 10 years ago, a new field of research focusing on the interaction of ionizing radiation with isolated gas-phase molecules of biological interest started to flourish. The work presented in this thesis represents an experimental effort to bridge the gap between gas-phase studies and radiobiology. Pioneering studies on the action of energetic photons and keV ions of more realistic systems in the gas phase, such as oligonucleotides as well as peptides and proteins, are presented.

Investigation of charge migration induced ultrafast photo-fragmentation of peptide and protein ions upon VUV and soft X-rays photo absorption was performed. For the experiments, a double tandem mass spectroscopy setup, based on the soft ionization technique of electrospray and a radiofrequency ion trap, was interfaced with synchrotron radiation sources at BESSY and MAXlab, and with the free electron laser FLASH. The results show that fragmentation patterns are dominated by ultrafast cleavage of sidechains of their amino acids. These might prevent further fragmentation on small peptides.