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Band-gap tunneling states in DNA
Hao Wang1, James P Lewis, Otto F Sankey
1Department of Physics and Astronomy, Brigham Young University, Provo, Utah 84602-4658, USA.
Physical Review Letters
|August 25, 2004
Summary
DNA electrical conductivity is limited by electron transfer rates. New calculations reveal that DNA is a poor tunneling conductor due to a high beta factor, even with a small band gap.
Area of Science:
- Molecular Biophysics
- Quantum Chemistry
- Genetics
Background:
- Electron (hole) transfer is crucial for DNA electrical conductivity.
- Transfer occurs via quantum tunneling (short distances) or thermally activated hopping (long distances).
- Tunneling probability depends on molecular length (L) and energy-dependent factor beta(E).
Purpose of the Study:
- To calculate beta(E) for DNA for the first time.
- To investigate electron tunneling in poly(dA)-poly(dT) and poly(dG)-poly(dC).
- To understand DNA's role as a tunneling conductor.
Main Methods:
- Complex band structure approach.
- Calculation of beta(E) in DNA.
- Analysis of tunneling probability dependence on molecular length and energy.
Main Results:
- Calculated beta(E) for poly(dA)-poly(dT) and poly(dG)-poly(dC) DNA.
- Found a very large beta value near DNA's midgap.
- Determined that DNA is a poor tunneling conductor.
- Observed faster tunneling decay in DNA compared to other organic molecules with wider gaps.
Conclusions:
- The high beta factor near midgap significantly hinders electron tunneling in DNA.
- DNA's poor tunneling conductivity is primarily due to this high beta value, not just its band gap.
- DNA exhibits rapid tunneling decay, making it less efficient for electrical conduction than anticipated.