Coherence-assisted electron diffusion across the multi-heme protein-based bacterial nanowire

Area of Science:

• Biochemistry
• Biophysics
• Microbiology

Background:

• Biological electron transfer (ET) is vital in cellular processes.
• Extracellular ET (EET) across bacterial nanowires occurs over micrometer distances.
• The structure of the conductive Geobacter sulfurreducens nanowire (OmcS protein) was recently elucidated.

Purpose of the Study:

• To propose and analyze models for long-range EET in bacterial nanowires.
• To investigate the role of protein structure and electron transport mechanisms.
• To explain the high conductivity observed in G. sulfurreducens nanowires.

Main Methods:

• Development of electron diffusion models incorporating hopping and coherent transport.
• Analysis of electron transport through chains of heme groups in the OmcS protein.
• Comparison of model predictions with experimental conductivity values.

Main Results:

• Pure hopping models struggle to explain observed conductivity with conventional parameters.
• A mixed hopping-coherent transport model shows superior electron diffusion.
• Coherent transport, facilitated by local protein rigidification and reduced reorganization energy, enhances long-range EET.

Conclusions:

• The classical hopping model is insufficient for explaining bacterial nanowire conductivity.
• A mixed hopping-coherent transport mechanism provides a more plausible explanation for efficient long-range EET.
• Protein structure plays a critical role in modulating electron transfer efficiency.