TARGETS, HITS AND TRACKS

Target theory was the first successful attempt to describe biological phenomena in the language of theoretical physics. Its basic assumptions are still valid, and their validity can be proven with the help of modern techniques of molecular biology. The theory has also practical implications, e.g. the determination of molecular weights of enzymes which cannot be easily separated to allow standard molecular analysis. For the description of heavy charged particle action the original concept had to be broadened which led to the development of “microdosimetry”. Track structure analysis takes into account the spatial distribution of energy deposition at a nanometer scale and thus allowed an understanding of the action of heavy charged particles which is important both for the assessment of radiation risk to humans as well as to subminiature electronic circuits. New developments in radiation biology as, e.g., the “bystander effect” do not call the basic principles into question but ask for a rethinking about the nature of targets and the possible effects following radiation interactions.