Investigating Electron Conductivity Regimes in the Bacterial Cytochrome Wire OmcS

Area of Science:

• Microbial electron transport
• Bioelectronics
• Computational biophysics

Background:

• Geobacter sulfurreducens produces conductive protein nanowires with potential applications in bioelectronics.
• These wires feature a linear arrangement of hemes, proposed to support electronic conductivity.
• Existing models fail to explain the experimentally observed high conductivity of these cytochrome wires.

Purpose of the Study:

• To investigate the role of dynamic disorder in the electronic properties of Geobacter sulfurreducens cytochrome wires.
• To resolve the discrepancy between theoretical predictions and experimental measurements of conductivity.
• To propose a mechanism for long-range electronic conduction in microbial nanowires.

Main Methods:

• Utilized Kohn-Sham density functional theory to extract charge carrier site information.
• Developed a quantum charge carrier model incorporating decoherence corrections as proxies for dynamic disorder.
• Simulated the influence of interheme geometry and electrostatic environment on energy landscapes.

Main Results:

• Site and coupling energies are highly sensitive to geometric and electrostatic variations.
• The quantum charge carrier model with decoherence corrections predicts diffusion coefficients closer to experimental values.
• Dynamic fluctuations in the electrostatic environment can transiently delocalize charge carriers.

Conclusions:

• Dynamic disorder, specifically environmental fluctuations, is crucial for understanding the high conductivity of microbial cytochrome wires.
• Instantaneous environmental fluctuations can lift energy degeneracies and facilitate charge delocalization.
• Findings provide insights for designing novel bio-inspired conductive materials based on heme structures.