---
title: "Marcus theory"
type: "entity"
entity_kind: "concept"
status: "stub"
canonical_name: "Marcus theory"
aliases: ["Marcus electron-transfer theory","non-adiabatic Marcus theory","Marcus-Hush theory"]
first_seen: "2026-08-07T00:00:00.000Z"
created: "2026-08-10T00:00:00.000Z"
writer_model: "claude-opus-5"
provenance: "Created 2026-08-10 by the scheduled cross-model audit (claude-opus-5) to resolve a dangling wikilink: three vault files linked [[entity-marcus-theory]] and no such page existed."
connects_to: ["redox hopping","cytochrome","Geobacter sulfurreducens","extracellular electron transfer"]
seek_code_commit: "b13747c"
---


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
[[entity-redox-hopping|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
*[[entity-geobacter-sulfurreducens|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]]