Hyperthermal Reactions in DNA Triggered by 1-20 eV Electrons: Absolute Cross Sections for Crosslinks, Strand Breaks,...

Area of Science:

• Radiation Biology
• Molecular Biophysics
• Nanotechnology

Background:

• High-energy radiation (HER) induces cellular damage, with low-energy electrons (LEEs) being significant secondary particles.
• Accurate absolute cross sections (ACSs) for LEE-induced DNA reactions are vital for radiobiological effectiveness calculations, especially in targeted radiotherapy.
• Understanding LEE-DNA interactions is key to predicting and mitigating radiation damage.

Purpose of the Study:

• To generate a comprehensive set of ACSs for various DNA damages induced by LEEs across an energy range of 1-20 eV.
• To provide essential data for modeling cellular damage and improving the efficacy of radiotherapy.
• To compare LEE-induced DNA damage in free plasmid DNA versus DNA complexed with arginine.

Main Methods:

• Utilized a mathematical model to derive ACSs from experimentally determined effective damage yields.
• Quantified direct and enzyme-revealed conformational damages in 3197 base-pair plasmid DNA films using electrophoresis.
• Generated ACSs for crosslinks, double-strand breaks (DSBs), single-strand breaks, base-damage-related crosslinks, non-DSB clustered damages (NDCDs), and isolated base damages.

Main Results:

• The first complete set of ACSs for LEE-induced DNA damages (crosslinks, DSBs, SSBs, etc.) were generated in the 1-20 eV range.
• ACSs showed strong energy dependence, with peak values at 10 eV.
• At 5 and 10 eV, total damage ACSs were substantially larger (63% and 80%, respectively) than for DNA bound to arginine.

Conclusions:

• Single LEE impacts can generate critical DNA lesions like DSBs, NDCDs, and crosslinks, threatening genetic stability.
• The generated ACSs provide crucial parameters for accurate radiobiological modeling and targeted radiotherapy.
• Free DNA is more susceptible to LEE-induced damage than DNA protected by histone-like proteins.