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Assessing Possible Mechanisms of Micrometer Scale Electron Transfer in Heme Free Geobacter Sulfurreducens Pili.

08:00 EDT 16th May 2019 | BioPortfolio

Summary of "Assessing Possible Mechanisms of Micrometer Scale Electron Transfer in Heme Free Geobacter Sulfurreducens Pili."

The electrically conductive pili of G. sulfurreducens are of both fundamental and practical interest. They facilitate extracellular and interspecies electron transfer and also provide an electrical interface between living and non-living systems. We examine the possible mechanisms of G. sulfurreducens electron transfer in regimes ranging from incoherent to coherent trans- port. For plausible ET parameters, electron transfer in G. sulfurreducens bacterial nanowires mediated only by the protein is predicted to be dominated by incoherent hopping between phenylalanine (Phe) and tyrosine (Tyr) residues that are 3 to 4 A ̊ apart, where Phe residues in the hopping pathways may create delocalized "islands." This mechanism could be accessible in the presence of strong oxidants, capable of oxidizing Phe and Tyr residues. We also examine the physical requirements needed to sustain biological respiration via nanowires. We find that the hopping regimes with ET rates on the order of 108/s between Phe islands and Tyr residues and conductivities on the order of mS/cm can support ET fluxes that are compatible with cellular respiration rates, although sustaining this delocalization in the heterogeneous protein environment may be challenging. Computed values of fully coherent electron fluxes through the pili are orders of magnitude too low to support microbial respiration. We suggest experimental probes of the transport mechanism based on mutant studies to examine the role of aromatic amino acids and of yet to be identified redox cofactors.

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Name: The journal of physical chemistry. B
ISSN: 1520-5207
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