Akademik Veri Yönetim Sistemi
JOURNAL OF PHYSICAL CHEMISTRY B, cilt.1, sa.1, ss.1-11, 2025 (SCI-Expanded)
Abstract:We investigate the spectroscopic properties and charge transfer (CT) processes in a tetrameric model of the homodimeric
reaction center of Heliobacterium modesticaldum (HbRC), and
presenting first-principles calculations based on Fermi’s Golden
Rule. HbRC represents the simplest known analog of other
photosynthetic systems and comprises the special pair, SP Pdimer molecule, adjacent cofactors Acc and Aoh, key amino
acid residues (His537, Gln458, and Ser545), and two water
molecules. Therefore, to assess the influence of the surrounding
nearby environment, we compare a ”naked” model—excluding
all amino acid residues—with a ”full” model that incorporates all nearby residues. We identify several bright states
in the reaction center that trigger subsequent CT processes
beyond the SP P dimer. Notably, one of the bright states,
characterized as (SP P AccAoh)∗, aligns with experimental observations. We also analyze the charge-separated configurations (SP P Acc)+(Aoh)− as the charge separation initial state
(CSI) and (SP P )+Acc(Aoh)− as the charge separation final (CSF) state, along with intermediate processes such as(SP P )+(Acc)−Aoh and SP P (Acc)+(Aoh)−. A key finding is
that most of the calculated CSF states are energetically lower
than the bright states, enabling electron transfer through a
downhill CT pathway. Also, CSI states energetically much lower
in the full model which in turn decrease the driving force energy that play explicitly on the rate. Most rates are found to lie
in the picosecond timescale. All electronic parameters are derived using an optimally tuned screened range-separated hybrid
functional within a polarizable continuum model, accounting
for varying dielectric constants.