Solvent fluctuations drive the hole transfer in DNA: a mixed quantum-classical study

Area of Science:

• Biophysics
• Computational Chemistry
• Molecular Biology

Background:

• DNA's role in charge transport is crucial for biological processes.
• Understanding charge transfer mechanisms in DNA is key to developing novel electronic devices.

Purpose of the Study:

• To investigate the mechanism of hole transfer across adenine bridges in double-stranded DNA.
• To elucidate the role of solvent dynamics and DNA conformational fluctuations in charge transport.

Main Methods:

• Utilized a multiscale approach combining time-dependent density functional theory (TD-DFT) with classical molecular dynamics (MD) simulations.
• Employed a quantum mechanics/molecular mechanics (QM/MM) scheme for accurate energy calculations.
• Propagated the hole through the DNA adenine bridge.

Main Results:

• Identified significant site energy fluctuations (~0.4 eV) induced by solvent degrees of freedom.
• Observed that these fluctuations promote charge-transfer active conformations with high transfer efficiency.
• Demonstrated a charge hopping mechanism operative in short adenine bridges (<4 adenines), differing from static tunneling models.
• Found that solvent fluctuations significantly correlate neighboring sites, enhancing charge transfer rates, while electronic coupling fluctuations have minor impact.

Conclusions:

• Solvent dynamics play a critical role in gating charge transfer in DNA.
• The study emphasizes the necessity of accurate solvent effect descriptions and proper conformational sampling for understanding DNA charge transport.
• Charge hopping, rather than static tunneling, is the dominant mechanism in short DNA bridges due to dynamic solvent effects.