Related Experiment Videos
Long-range oxidative damage to cytosines in duplex DNA
Fangwei Shao1, Melanie A O'Neill, Jacqueline K Barton
1Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
Summary
Charge transport in DNA involves all bases, not just guanine. This dynamic delocalization model explains DNA
Area of Science:
- Biophysics
- Molecular Biology
- Organic Chemistry
Background:
- Charge transport (CT) through DNA is sensitive to intervening structures and often described as charge-hopping between guanine sites.
- Previous models focused on low-energy guanine sites for charge migration.
Purpose of the Study:
- To investigate the role of higher-energy pyrimidine bases in DNA charge transport.
- To elucidate the mechanism of hole migration in DNA assemblies.
Main Methods:
- Utilized a kinetically fast electron hole trap, N(4)-cyclopropylcytosine ((CP)C).
- Employed DNA assemblies with high-energy photooxidants ([Rh(phi)(2)(bpy')](3+) or anthraquinone derivative).
- Analyzed oxidative damage at distant (CP)C sites and modulated yields by guanine sites.
Main Results:
- Observed significant oxidative damage at (CP)C, indicating involvement of higher-energy bases in hole migration.
- Demonstrated comparable trapping efficiencies for N(4)-cyclopropylcytosine ((CP)C) and N(2)-cyclopropylguanosine ((CP)G).
- Showed that CT efficiency depends on orbital mixing among bases, not just isolated base energies.
Conclusions:
- Propose a dynamic delocalized model where charge migration involves all DNA bases within transient, structure-dependent domains.
- This model reconciles DNA CT sensitivity to sequence-dependent structure.
- Provides a framework for exploiting DNA CT chemistry and physics.