Repair Kinetics of DSB-Foci Induced by Proton and α-Particle Microbeams of Different Energies

In this work, the induction and repair of radiation-induced 53BP1 foci were studied in human umbilical vein endothelial cells irradiated at the PTB microbeam with protons and alpha-particles of different energies. The data were analyzed in terms of the mean number of 53BP1 foci induced by the different ion beams. The number of 53BP1 foci found at different times post-irradiation suggests that the disappearance of foci follows first order kinetics. The mean number of initially produced foci shows the expected increase with LET. The most interesting finding of this work is that the absolute number of persistent foci increases with LET but not their fraction. Furthermore, protons seem to produce more persistent foci as compared to alpha-particles of even higher LET. This may be seen as experimental evidence that protons may be more effective in producing severe DNA lesions, as was already shown in other work, and that LET may not be the best suited parameter to characterize radiation quality.

Automated summary

In this study, the induction and repair of radiation-induced 53BP1 foci were examined in human umbilical vein endothelial cells irradiated with protons and alpha-particles of varying energies. The analysis of data revealed that the disappearance of foci follows first order kinetics. Interestingly, the absolute number of persistent foci increased with energy loss but their fraction remained constant. Protons were found to produce more persistent foci compared to even higher energy loss alpha-particles, suggesting that protons may be more effective in causing severe DNA damage.