Influence of incident particle energy on DNA damage formation in a pUC19 plasmid: A Geant4-DNA study

Understanding how radiation quality and particle energy influence DNA damage formation is essential for radiation biology, radiation protection, and particle therapy applications. In this study, the Geant4-DNA track-structure Monte Carlo toolkit (version 11.3.0) was employed to investigate DNA damage formation in a geometrically explicit pUC19 plasmid model following electron and proton irradiation. The simulations incorporated detailed particle transport in liquid water, radiation chemistry, and DNA damage scoring capabilities provided by the Geant4-DNA framework. Simulations were performed for monoenergetic electrons (0.1 keV–3 MeV) and protons (0.1–100 MeV). DNA damage was quantified in terms of single-strand breaks (SSBs), double-strand breaks (DSBs), and damage complexity using the built-in Geant4-DNA plasmid damage scorer. To ensure reliable statistics across the investigated energy spectrum, an adaptive sampling strategy ranging from 10 4 to 10 7 primary particles was employed depending on particle energy. The results demonstrated a pronounced dependence of DNA damage formation on both particle type and incident energy. Electron-induced strand-break yields exhibited a maximum near 1 keV and decreased progressively at higher energies. In contrast, proton irradiation produced substantially larger DNA damage yields, with maximum strand-break and DSB production occurring at 0.1 MeV. The highest proton-induced DSB yield exceeded the maximum electron induced DSB yield by more than an order of magnitude. Proton irradiation also generated considerably higher levels of complex DNA damage and larger DSB-to-strand-break ratios, indicating enhanced clustering efficiency under dense ionization conditions.