Effect of the Environment on the Excitation Energy and Charge Transfer Pathways of the Heliobacterium modesticaldum Reaction Center

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dc.contributor.authorErturk, Murat
dc.contributor.authorAksu, Huseyin
dc.date.accessioned2026-02-03T12:02:30Z
dc.date.available2026-02-03T12:02:30Z
dc.date.issued2025
dc.departmentÇanakkale Onsekiz Mart Üniversitesi
dc.description.abstractThe spectroscopic properties and charge transfer (CT) processes in a tetrameric model of the homodimeric reaction center of Heliobacterium modesticaldum (HbRC) are presented. HbRC represents the simplest known analogue of other photosynthetic systems and comprises the special pair, SPP dimer 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 nearby surrounding 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 that of the SPP dimer. Notably, one of the bright states, characterized as (SPP AccAoh)*, aligns with experimental observations. We also analyze the charge-separated configurations (SPPAcc)(+)(Aoh)(-) as the charge separation initial state (CSI) and (SPP)(+) Acc (Aoh)(-) as the charge separation final (CSF) state, along with intermediate processes such as (SPP)(+)(Acc)(-)Aoh and SPP(Acc)(+)(Aoh)(-). A key finding is that most of the calculated CSF states are energetically lower than those of the bright states, enabling electron transfer through a downhill CT pathway. Additionally, CSI states are energetically much lower in the full model, which in turn decreases the driving force energy that explicitly affects the rate. We have employed first-principles calculations based on Fermi's golden rule for the two models. Most rates are found to lie in the picosecond time scale, which is in line with observations. All electronic parameters are derived by using an optimally tuned screened range-separated hybrid functional within a polarizable continuum model, accounting for varying dielectric constants.
dc.description.sponsorshipTrkiye Bilimsel ve Teknolojik Arastirma Kurumu [123Z591, TUBITAK 1001]
dc.description.sponsorshipScientific and Technological Research Council of Turkiye (TUBITAK)
dc.description.sponsorshipTUBITAK
dc.description.sponsorshipThis study was supported by the Scientific and Technological Research Council of Turkiye (TUBITAK) under Grant Number 123Z591 (TUBITAK 1001). The authors M.E. and H.A. thank TUBITAK for their support. We are thankful to Canakkale Onsekiz Mart University Faculty of Sciences for providing computing facilities and making the resources available to complete the reported research.
dc.identifier.doi10.1021/acs.jpcb.5c04126
dc.identifier.endpage10720
dc.identifier.issn1520-6106
dc.identifier.issn1520-5207
dc.identifier.issue41
dc.identifier.pmid41045499
dc.identifier.scopus2-s2.0-105018737922
dc.identifier.scopusqualityQ2
dc.identifier.startpage10711
dc.identifier.urihttps://doi.org/10.1021/acs.jpcb.5c04126
dc.identifier.urihttps://hdl.handle.net/20.500.12428/34784
dc.identifier.volume129
dc.identifier.wosWOS:001586998700001
dc.identifier.wosqualityQ3
dc.indekslendigikaynakWeb of Science
dc.indekslendigikaynakScopus
dc.indekslendigikaynakPubMed
dc.language.isoen
dc.publisherAmer Chemical Soc
dc.relation.ispartofJournal of Physical Chemistry B
dc.relation.publicationcategoryMakale - Uluslararası Hakemli Dergi - Kurum Öğretim Elemanı
dc.rightsinfo:eu-repo/semantics/closedAccess
dc.snmzKA_WOS_20260130
dc.subjectPhotosynthetic Reaction-Center
dc.subjectDensity-Functional Theory
dc.subjectTransfer States
dc.subjectRational Design
dc.subjectAb-Initio
dc.subjectBacteriochlorin
dc.subjectBenchmarking
dc.titleEffect of the Environment on the Excitation Energy and Charge Transfer Pathways of the Heliobacterium modesticaldum Reaction Center
dc.typeArticle

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