[Todos] Coloquios del Departamento de Física

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                      COLOQUIOS DEL DEPARTAMENTO DE FÍSICA FCEyN - UBA

                              http://coloquios.df.uba.ar/

                               Charla, café y galletitas
                      En el Aula Federman, 1er piso, Pabellón I,
                                Ciudad Universitaria

                              Jueves 25 de noviembre, 14hs,


                      Stopping power of biomolecules for fast ions


                                     Stephan Sauer

                               Department of Chemistry
                                Copenhagen University




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 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.