Excess electron interactions with solvated DNA nucleotides: strand breaks possible at room temperature

Area of Science:

• Biophysics
• Radiation Chemistry
• Molecular Biology

Background:

• Ionizing radiation generates low-energy electrons (<20 eV) in biological matter.
• These electrons interact with DNA, with nucleobases showing high electron affinity.
• Previous research indicated nucleobases attract these excess electrons in solvated DNA fragments.

Purpose of the Study:

• To investigate the longer-term effects of low-energy electrons on DNA.
• To determine the free energy barriers for phosphodiester C(3')-O(3') bond cleavage in solvated nucleotides.
• To assess the potential of low-energy electrons to induce DNA strand breaks.

Main Methods:

• First-principles computational study.
• Calculation of free energy barriers for bond cleavage in fully solvated nucleotides.
• Analysis of electron-induced DNA damage mechanisms.

Main Results:

• Free energy barriers for phosphodiester C(3')-O(3') bond cleavage were calculated for solvated nucleotides.
• Except for deoxyadenosine monophosphate (dAMP), barriers were approximately 6 kcal/mol.
• These low barriers suggest regular bond cleavage at 300 K due to solvent and thermal fluctuations.

Conclusions:

• Low-energy electrons can lead to DNA strand breaks.
• The cleavage of the phosphodiester C(3')-O(3') bond is a likely outcome.
• Findings support the role of low-energy electrons in DNA damage.