Excess electron trapping in duplex DNA: long range transfer via stacked adenines

Area of Science:

• Biophysics
• Molecular Biology
• Radiation Chemistry

Background:

• Charge transfer (CT) in DNA is crucial for understanding ionizing radiation effects and potential applications in DNA nanotechnology.
• Energy deposition in DNA generates holes and excess electrons (EEs), initiating damage pathways.
• Excess electron transfer (EET) is a key process in DNA CT.

Purpose of the Study:

• To investigate the mechanisms of EET in DNA using Electron Paramagnetic Resonance (EPR) spectroscopy.
• To determine the role of base composition and sequence in directing EE trapping and transfer within DNA.
• To elucidate the potential of DNA as a medium for charge transport.

Main Methods:

• Irradiation of oligodeoxynucleotides at 4 K.
• Electron Paramagnetic Resonance (EPR) spectroscopy to detect and characterize trapped excess electrons.
• Analysis of EE distribution and trapping sites based on DNA sequence.

Main Results:

• Stretches of consecutive adenine bases (A) facilitate intrastrand EET in duplex DNA at 4 K.
• Adenine efficiently traps EEs only when it is not adjacent to thymine (T), cytosine (C), or guanine (G).
• Thymine competes with adenine for EE trapping, while cytosine is a more effective trap than thymine, often serving as an endpoint for EET.

Conclusions:

• DNA sequence significantly influences the pathway and efficiency of excess electron transfer.
• Adenine-rich sequences act as conduits for EET, with trapping sites determined by neighboring bases.
• Understanding EET in DNA has implications for radiation-induced damage, DNA repair mechanisms, and the development of DNA-based nanoscale electronic components.