Charge equilibration between two distinct sites in double helical DNA

Area of Science:

• Molecular Biology
• Biochemistry
• Physical Chemistry

Background:

• DNA charge transport is a fundamental process with implications for DNA repair and signaling.
• Understanding the dynamics and directionality of charge transport is key to elucidating DNA's functional mechanisms.

Purpose of the Study:

• To investigate long-range charge transport through DNA base pair stacks.
• To explore the role of radical trapping sites in DNA charge transport dynamics.
• To determine the directionality and equilibration of charge transport in DNA.

Main Methods:

• Construction of chemically defined DNA assemblies with specific oxidative traps (methylindole and 5'-GGG-3' sites).
• Utilizing flash/quench technique and transient absorption spectroscopy to monitor radical formation.
• Quantifying oxidative damage yields via gel electrophoresis.

Main Results:

• Base radicals form rapidly (> or =10(7) s(-1)) within the DNA assemblies.
• The 5'-GGG-3' site acts as an effective secondary radical trap, reducing methylindole oxidation yield.
• Charge transport yields are independent of the orientation of the trapping sites.

Conclusions:

• DNA charge transport is a dynamic process, with radical propagation occurring in both forward and reverse directions.
• Charge equilibration across the DNA duplex is fast compared to trapping events.
• These findings highlight the importance of considering bidirectional radical propagation in DNA charge transport.