Voltage-induced long-range coherent electron transfer through organic molecules.

Area of Science:

• Biophysics
• Molecular Biology
• Organic Electronics

Background:

• Biological systems utilize charge transfer for essential functions like energy conversion and signaling.
• Unlike synthetic circuits, biological charge transport occurs through nominally insulating biomolecules.
• Long-distance charge transport in biomolecules is often explained by thermally activated hopping, but experimental data show limited temperature dependence.

Purpose of the Study:

• To propose and explain a temperature-independent mechanism for long-distance charge transport in biomolecules.
• To account for experimental observations of limited temperature dependence in electron transfer over nanometer scales.
• To provide a unifying mechanism for charge transport in diverse molecular systems.

Main Methods:

• Theoretical modeling of electron transfer mechanisms.
• Analysis of electric potential and its effect on molecular electronic states.
• Comparison of the proposed mechanism with experimental data from DNA, organic semiconductors, and peptides.

Main Results:

• A novel mechanism based on voltage-induced electric potential differences driving resonant tunneling.
• Demonstration that this mechanism explains temperature-independent charge transport in DNA.
• Explanation for strongly voltage-dependent currents observed in organic semiconductors and peptides.

Conclusions:

• The proposed voltage-driven resonant tunneling mechanism offers a new perspective on biological charge transport.
• This mechanism is general and applicable to molecules with wide energy windows around the HOMO-LUMO gap.
• It reconciles experimental findings that challenge traditional thermally activated hopping models.