Resonant electron capture by 5-Br-2'-deoxyuridine

Area of Science:

• Physical Chemistry
• Chemical Physics
• Molecular Physics

Background:

• 5-Br-2 -deoxyuridine (BrdUrd) is a radiosensitizing agent.
• Understanding electron-molecule interactions is crucial for radiosensitizer mechanisms.
• Previous quantum-chemical calculations predicted BrdUrd's negative ion structure.

Purpose of the Study:

• To investigate resonant electron capture by BrdUrd molecules.
• To characterize the negative ions formed and their decay pathways.
• To determine the electronic affinity and fragmentation cross-sections of BrdUrd.

Main Methods:

• Study of resonant electron capture across electron energies from 0 to 14 eV.
• Analysis of negative ion formation, autoneutralization, and dehalogenation kinetics.
• Estimation of electronic affinity and dissociative electron attachment cross-section.

Main Results:

• Long-lived molecular negative ions were observed in the thermal energy range.
• The most probable structure involves an extended C-Br bond, consistent with theoretical predictions.
• Significant electronic affinity (0.93-1.38 eV) and a high cross-section for Br- ion formation (≥1.65 × 10^-15 cm^2) were determined.
• Formation of reactive deoxyuridine-5-yl radicals was indirectly confirmed.

Conclusions:

• Electron capture by BrdUrd leads to the formation of transient negative ions.
• The decay of these ions produces bromide ions and deoxyuridine-5-yl radicals.
• The findings support the role of these radicals in the radiosensitizing properties of BrdUrd.