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Bound anionic states of adenine
Maciej Harańczyk1, Maciej Gutowski, Xiang Li
1Department of Chemistry, University of Gdańsk, 80-952 Gdańsk, Poland.
Summary
Researchers discovered new anionic tautomers of adenine that are stable in condensed phases, unlike previous findings. These valence anionic states may play a role in DNA damage from low-energy electrons.
Area of Science:
- Chemical Physics
- Molecular Biophysics
- Quantum Chemistry
Background:
- Anionic states of nucleic acid bases are crucial for DNA damage by low-energy electrons and charge transfer.
- Previous studies on free nucleic acid bases primarily observed dipole-bound states, not relevant to condensed phases.
- Valence anionic states of purine bases were thought to be unbound in condensed environments.
Purpose of the Study:
- To investigate the existence and properties of valence anionic states in nucleic acid bases, specifically adenine.
- To challenge the prevailing assumption that valence anionic states of purine bases are adiabatically unbound.
- To explore the potential relevance of these states in biological systems and DNA damage.
Main Methods:
- Developed a novel experimental method for preparing parent anions of nucleic acid bases for photoelectron experiments.
- Employed a combinatorial/quantum chemical approach to identify stable tautomers of organic molecules.
- Utilized photoelectron spectroscopy to probe the electronic structure and stability of anionic tautomers.
Main Results:
- Identified previously overlooked adenine tautomers (enamine-imine) that support stable valence anionic states.
- Observed significant electron vertical detachment energies up to 2.2 eV for these new anionic tautomers.
- Demonstrated that at least one of these anionic tautomers is adiabatically bound, contrary to prior expectations.
- Predicted that these anionic tautomers likely dominate in solution and exhibit enhanced stability compared to canonical forms.
Conclusions:
- The discovery of stable valence anionic states in adenine tautomers challenges existing models of electron interactions with DNA bases.
- These newfound anionic states, unlike dipole-bound states, can exist in condensed phases and are relevant to radiobiological damage.
- The findings suggest a revised understanding of how low-energy electrons interact with DNA and RNA, impacting radiobiology and genetic material stability.
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