Long-Range Conductivity in Proteins Mediated by Aromatic Residues

Area of Science:

• Biophysics
• Molecular Electronics
• Computational Biology

Background:

• Proteins lacking redox cofactors exhibit significant electrical conductance over nanometer distances.
• Observed electron transport is faster than predicted by conventional electron transfer theories, posing a scientific puzzle.

Purpose of the Study:

• To elucidate the molecular mechanism behind unexpectedly fast electron transport in non-redox-active proteins.
• To reconcile experimental observations with theoretical predictions using advanced simulation techniques.

Main Methods:

• Combined all-atom molecular dynamics (MD) simulations with electron transfer theory.
• Analyzed consensus tetratricopeptide repeats, a non-redox-active protein system.
• Calculated reorganization energies from electrostatic energy fluctuations.

Main Results:

• MD simulations revealed that protein non-ergodic sampling leads to significantly reduced reaction-reorganization energies (∼0.2 eV).
• This lower reorganization energy facilitates long-range conductivity, aligning with experimental findings.
• Calculated current decay with distance matched experimental data.

Conclusions:

• A novel mechanism involving reduced reorganization energies explains fast protein electrical conductance.
• This mechanism enables efficient electron transport without relying on quantum coherent transport.
• The findings advance the understanding of charge transport in biological molecules.