BIOPHYSICAL ASPECTS OF AUGER PROCESSES

Radionuclide decay by electron capture and/or internal conversion is a ccompanied by complex atomic vacancy cascades and emission of low-ener gy electrons, resulting in a highly charged daughter atom and a high d ensity of electron irradiation in the immediate vicinity of the decay site. The molecular and cellular consequences of such decay events inc lude DNA strand breaks, mutations, chromosome aberrations, malignant t ransformation, division delay, and cell death. Damage to cells depends largely on the intracellular location of the radionuclide, Decays out side the cell nucleus produce low-LET-type radiation effects (RBE simi lar to 1). In contrast, decays in DNA cause pronounced high-LET-type e ffects (RBE similar to 7-9). However, recent studies suggest that even for DNA-associated Auger emitters cell damage can be modified to rese mble the pattern observed with low-LET radiations. These findings indi cate that the molecular and cellular mechanism(s) responsible for the cytotoxic effects of Auger emitters remain obscure.