Fundamental mechanisms & applications of low energy ion, electron, and photon interactions with biomolecular systems

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Although most of the energy deposited by ionizing radiation (energetic heavy ions, electrons or UV, X-ray, or gamma-rays) in living tissue is quickly channeled into production of abundant secondary ion fragments, radicals and electrons, traditional radiation science has largely ignored the early effects of many of these secondary particles, mainly ions and electrons. However, our previous work [Science 287, 1658 (2000)] has shown for the first time that even at unprecedented low energies their reactions lead to lethal breaks in DNA and the destruction of nucleic acid bases, whose sequence provides the actual genetic text inside the DNA; moreover, this leads to further production of numerous types of very reactive secondary ions. What is still not known is this: by what mechanisms do such ions initiate subsequent damage in DNA, or other important biomolecules. Our research will focus on the detailed reactions by which such ions can damage or modify DNA, using our novel technologies of microanalysis recently developed from methods of ion and electron beam physical chemistry, synchrotron accelerator technology, and biochemical radiation sciences. Moreover, our research will uncover the fundamental differences of how and by what mechanisms molecular damage is induced by the different types of radiation (ions, electrons and UV or X-rays). This multidisciplinary approach will complete our knowledge of the molecular origins of radiation damage, particularly by ions, and how this may promote cell death and mutations; such knowledge is essential for realistic radiation risk assessments for airline crews and astronauts (exposed to ionic space radiation), or reactor workers, and in cancer radiotherapy. The results of our studies will also provide knowledge to help us in the future to devise crucial new methods to control, or reduce, the side effects of radiation exposure, for example by designing new chemicals that protect DNA from such radiation, or sensitize cancer cells to therapeutic radiation, leading to lower dose to healthy tissue, thus less side effects.