Double strand breaks (DSB) in nuclear DNA are one type of radiation-induced damage identified as being particularly deleterious. The calculation of these damages using Monte Carlo track structure modelling, which is made possible by the Geant4-DNA toolkit, could be a good indicator to better appreciate and anticipate the side effects of radiation therapy. However, in order to obtain accurate simulated results, a cell nucleus geometry as realistic as possible must be used. In this work, we present simulation results with a new model of an endothelial cell nucleus in which the levels of chromatin compaction are distributed along the genome according to the isochore theory. In a comparative study with a previous nuclear geometry, simulations are conducted for proton LET of 4.29 keV/µm, 19.51 keV/µm and 43.25 keV/µm. The organization of the chromatin fiber into different levels of compaction linked to isochore families leads to an increase of 3-10% in DSB yield and makes it possible to identify the most affected part of the genome. New results indicate that, the genome core is more radiosensitive than the genome desert. This study highlights the importance of an advanced modelling of the distribution of the chromatin compaction levels for the calculation of the radio-induced damage.< Leer menos