Quantum chemical study for radical-induced DNA effects and damage

Area of Science:

• Computational Chemistry
• Molecular Biology
• Chemical Kinetics

Background:

• DNA damage can occur through various chemical reactions, including radical interactions.
• Understanding molecular interactions with radicals is crucial for elucidating DNA damage mechanisms.
• Methyl radicals (Me-radical) are implicated in chemical modifications of DNA bases.

Purpose of the Study:

• To investigate the molecular interactions between DNA bases (adenine, guanine, cytosine) and methyl radicals.
• To elucidate the molecular mechanisms underlying DNA damage caused by methyl radicals.
• To identify the preferred reaction sites and relative reactivities of DNA bases towards methyl radicals.

Main Methods:

• Utilized perturbation analysis, a quantum chemical method, to study molecular interactions.
• Examined the reaction of methyl radicals with individual deoxyribonucleosides (dA, dG, dC).
• Investigated the reaction of methyl radicals with DNA base pairs (G-C and A-T).

Main Results:

• Guanine (dG) and adenine (dA) derivatives showed over 10 times higher reactivity towards methyl radicals compared to cytosine (dC).
• The primary methylation sites identified were the C(8) position of the purine ring in dA and dG, and the C(5) position of the pyrimidine ring in dC.
• In DNA, the purine ring of guanine within G-C base pairs preferentially reacted with methyl radicals, yielding 8-methyl-guanines.

Conclusions:

• Guanine and adenine exhibit significantly higher susceptibility to methyl radical attack than cytosine.
• Specific sites on purine (C8) and pyrimidine (C5) rings are preferential targets for methylation.
• The study provides molecular-level insights into DNA damage mechanisms involving methyl radicals, highlighting the preferential reaction at guanine bases in DNA.