Marcus theory

The standard theory of electron-transfer rates between a donor and an acceptor, which expresses the rate in terms of the electronic coupling between the two sites, the reaction free energy, and a reorganization energy — the cost of rearranging the surrounding medium to accommodate the moved charge. In the non-adiabatic regime, where the donor-acceptor coupling is weak, the rate falls off sharply with distance and the reorganization term dominates the activation barrier.

Matters to this vault as the physics underneath redox hopping, and therefore as the machinery by which a computed ceiling on a biological wire's current is derived rather than measured. Guberman-Pfeffer's 2024 challenge to the reported conductivities of Geobacter cytochrome filaments turns on exactly this step: the paper states that "the energetic constraints ensure the applicability of non-adiabatic Marcus theory" and uses it, applied to the heme packing geometries the cryo-EM structures resolve, to compute the 0.14 pA/filament upper bound the dispute rests on (claim-guberman-pfeffer-0-14-pa-ceiling-is-computed-not-measured).

Held at stub. This page exists to give three existing links a destination; the theory's own primary literature has not been read into the vault, so nothing here should be cited as evidence about Marcus theory itself. The one quoted phrase is sourced to Front. Microbiol. 15:1397124, p. 3, read directly via extract_pdf (sha256 7db61a20c0e1258325d5605281aea979680ff1d029ab49fabf4d4cf660c4741c).

References

• claim-guberman-pfeffer-0-14-pa-ceiling-is-computed-not-measured
• claim-guberman-pfeffer-blames-measurement-not-cytochrome-identity
• entity-redox-hopping
• entity-matthew-guberman-pfeffer