Physical events in the track structure of heavy ions and their relation to alterations of biomolecules.

Heavy charged particles interacting with biological cells can produce a wide variety of different physical, chemical and biological consequences. A rigorous identification of relevant chemical and biological alterations of biomolecules in cells, however, is still lacking and, thus, it is difficult to identify the potential biological importance of different early physical events. In addition, due to experimental and theoretical problems also little is known about the details of energy transfer, -absorption and -decay from projectiles to atoms/molecules in condensed targets; this is particularly true for not completely stripped heavy ions. Nevertheless, one might conclude from available data that higher densities of physical energy absorption events have a significantly higher probability to lead to qualitatively more severe biochemical alterations as regards the induction of DNA double strand breaks and of chromatin damage. It is not very likely that energy migration along the DNA molecule in biological cells over long distances plays a significant role as contributor to these biological radiation effects.