Structure constrained spin responses of an FMN superoxide radical-pair model in mitochondrial complex I

An FMN-centred range of accessible oxygen geometries in human mitochondrial complex I yields a near-contact maximum in a composite score, peaking near 3.3.

• Why it matters: Reaction-yield sensitivity of complex I’s FMN superoxide radical-pair depends on pocket geometry, but how accessible oxygen positions shape singlet yields under varying fields and dephasing is unclear.
• What they did: The study combined steric sampling of oxygen positions in human complex I with radical-pair spin simulations, generating singlet yields across FMN O2 centroid separations, magnetic fields, and spin-dephasing conditions.
• The result: The composite score peaked near 3.3 in the reference 2.5 ~9.0 calculation; the top 10% of accessible configurations had mean separation 3.28 (2.5th~97.5th percentiles, 2.77~3.64), and the near-contact maximum persisted under varied structural inputs and rates.