Electron interaction with a DNA duplex: dCpdC:dGpdG.

Area of Science:

• Computational Chemistry
• Molecular Biophysics
• Quantum Biology

Background:

• Cytosine-rich DNA sequences are crucial in various biological processes.
• Understanding electron attachment mechanisms in DNA is vital for DNA damage and repair studies.
• Previous studies have explored electron interactions with DNA, but detailed mechanisms in double-stranded, cytosine-rich systems are less understood.

Purpose of the Study:

• To investigate electron attachment to a minimal double-stranded cytosine-rich DNA model (dCpdC:dGpdG).
• To determine the energetics and localization of excess electrons.
• To explore the role of proton transfer and inter-strand interactions in stabilizing radical anions.

Main Methods:

• Density Functional Theory (DFT) calculations were employed.
• Calculations focused on electron affinity, radical anion formation, and proton transfer pathways.
• Analysis included electronic transitions and predicted visible absorption spectra.

Main Results:

• A significant electron affinity of approximately 2.2 eV was found for cytosine-centered radical anion formation.
• Excess electrons can localize at either the 5' or 3' position of cytosine.
• Inter-strand proton transfer leads to more stable distonic radical anions (1-4 kcal mol⁻¹ more stable).

Conclusions:

• Electron attachment to cytosine-rich DNA can form stable radical anions, influenced by proton transfer.
• The study predicts visible absorption bands (500-700 nm) for these radical anions, suggesting potential color changes in DNA.
• These findings offer insights into electron transfer mechanisms and potential photophysical properties of DNA.