Activationless Charge Transport in Heliobacterial Reaction Centers: Polarizable Cofactors Coupled to Strong Intraprotein Electric Fields
Abstract
We study rate-limiting steps of electron transfer following photoinduced charge separation to the primary acceptor A0 in a heliobacterial reaction center (HbRC). Two steps involved are electron transfer to the iron-sulfur cluster (ISC) FX of HbRC, followed by electron transfer to the FA ISC of a ferredoxin protein in solution. Ferredoxin forms a stable binding configuration with the reaction center as established by Brownian dynamics simulation. Molecular dynamics simulations are used to calculate the reaction times of ∼ 0.1µs (A0 → FX) and ∼ 3− 5µs (FX → FA). These two steps are the slowest in the overall electron transport in HbRC. Electron transfer to ferredoxin is irreversible since the calculated time of recombination to the closest A0 cofactor is ∼ 70 ms. All reactions show near-zero activation barriers when cofactors’ polarizabilities are included in the calculations. The overall robust operation of solar energy conversion in HbRCs is allowed by combining cofactors’ polarizabilities with strong local intraprotein electric fields.
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BibTeX
@misc{pirnia2026activationless,
title = {{Activationless Charge Transport in Heliobacterial Reaction Centers: Polarizable Cofactors Coupled to Strong Intraprotein Electric Fields}},
author = {Mohammad Mehdi Pirnia and Setare Mostajabi Sarhangi and Chun Kit Chan and Abhishek Singharoy and Kevin Redding and Dmitry V. Matyushov},
howpublished = {ChemRxiv},
year = {2026},
month = oct,
doi = {10.26434/chemrxiv.15010001/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010001/v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Activationless Charge Transport in Heliobacterial Reaction Centers: Polarizable Cofactors Coupled to Strong Intraprotein Electric Fields
AU - Mohammad Mehdi Pirnia
AU - Setare Mostajabi Sarhangi
AU - Chun Kit Chan
AU - Abhishek Singharoy
AU - Kevin Redding
AU - Dmitry V. Matyushov
PY - 2026
DA - 2026/10/06
PB - ChemRxiv
DO - 10.26434/chemrxiv.15010001/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010001/v1
AB - We study rate-limiting steps of electron transfer following photoinduced charge separation to the primary acceptor A0 in a heliobacterial reaction center (HbRC). Two steps involved are electron transfer to the iron-sulfur cluster (ISC) FX of HbRC, followed by electron transfer to the FA ISC of a ferredoxin protein in solution. Ferredoxin forms a stable binding configuration with the reaction center as established by Brownian dynamics simulation. Molecular dynamics simulations are used to calculate the reaction times of ∼ 0.1µs (A0 → FX) and ∼ 3− 5µs (FX → FA). These two steps are the slowest in the overall electron transport in HbRC. Electron transfer to ferredoxin is irreversible since the calculated time of recombination to the closest A0 cofactor is ∼ 70 ms. All reactions show near-zero activation barriers when cofactors’ polarizabilities are included in the calculations. The overall robust operation of solar energy conversion in HbRCs is allowed by combining cofactors’ polarizabilities with strong local intraprotein electric fields.
ER -