Fig. 2

Particle irradiation results in a prolonged block in the G2 phase. Percentage of cells in G2/M phase of four EC cell lines at 24 h after irradiation with biologically isoeffective doses of photons (X), protons (¹H) and heavy ions (¹²C, ¹⁶O) at a low dose level (left bars) and a high dose level (right bars) (mean and SD of n = 3 replicate samples). For clarity the low dose and high dose data is shown separately; the control groups are identical in both parts because for each radiation modality both dose levels were applied in the same experiment with one common control group per time point. *p < 0.05, **p < 0.01 (two-sided Student’s t-test between the indicated groups). For test comparing different radiation modalities were the control levels were subtracted from the