Ion-induced biomolecular radiation damage:: From isolated nucleobases to nucleobase clusters

A large number of studies ore devoted to the investigation of the biomolecular ionization and fragmentation dynamics underlying biological radiation damage. Most of these studies have been based on gas-phose collisions with isolated DNA building blocks. The rodiobiologicol significance of these studies is often questioned because of the lock of a chemical environment. To clarify this aspect, we studied interactions of keV ions with isolated nucleobases and with nucleobase clusters by means of coincidence time-of-flight spectrometry. Significant changes already show up in the molecular fragmentation patterns of very small clusters.