Near 0 eV electrons attach to nucleotides.

Area of Science:

• * Computational chemistry
• * Molecular modeling
• * Radiation chemistry

Background:

• * Understanding the initial steps of DNA damage by low-energy electrons is crucial.
• * Nucleotides are the fundamental building blocks of DNA and are susceptible to electron interactions.

Purpose of the Study:

• * To investigate the mechanism of DNA strand breakage initiated by low-energy electron attachment to nucleotides.
• * To model the electron attachment process using theoretical calculations.

Main Methods:

• * Employed the B3LYP/DZP++ theoretical approach for calculations.
• * Studied electron attachment to 2'-deoxycytidine-3'-monophosphate (3'-dCMPH) and its deprotonated form (3'-dCMP(-)).
• * Analyzed radical anion formation in both gas and aqueous phases.

Main Results:

• * 3'-dCMPH captures near 0 eV electrons, forming a stable radical anion with excess electron density on the base.
• * The pyrimidine-based radical anion exhibits high electron detachment energy, enabling subsequent C-O or glycosidic bond cleavage.
• * Phosphate-centered radical anions may be stable in aqueous solution but not in the gas phase.

Conclusions:

• * Low-energy electron attachment to nucleotides can lead to DNA strand breakage via radical anion intermediates.
• * The electron affinity of nucleotides is unaffected by counterions in aqueous solutions.
• * Incident electrons below 4 eV may not efficiently produce phosphate-centered radical anions.