Stephan Sauer

Department of Chemistry - Copenhagen University

Jueves 25/11/2010, 14 hs
Aula Federman, 1er piso, Pabellón I 

Understanding the basic physics of the interaction of radiation with biological targets becomes ever more important as we seek to protect healthy cells from radiation damage and to target therapeutic radiation (e.g., in the form of proton or C6+ ion beams) selectively on pathologic cells. The problem of describing and understanding the effects of radiological action on biological systems is exceedingly complicated, as one must describe long chains of sequential and parallel chemical and physical events, as well as possible nonlinearities between initial radiogenic molecular changes and final biological effects. All of the involved processes must be well-understood to deal effectively with problems such as radiation protection and radiation therapy. However, in all cases, the understanding and description of radiological action on biosystems begins with the determination of the energy deposited. In this seminar the results of our recent computational studies [1-9] of the mean excitation energy of the main ingredients of biological material water, aminoacids and nucleobases will be presented. The dependence on the conformations of the biomolecules, the influence of hydrogen bonding and surrounding water, the sensitivity to the orientation of the target molecule with respect to the ion beam direction will be discussed. Finally it will be illustrated how the mean excitation energy of larger biomolecules can be obtained using the Bragg rule, which breaks the molecular stopping power down in contributions from atomic cores and bonds.