Spectral characterization of the main pigments in the plant photosynthetic apparatus by theory and experiment

Götze, Jan P.; Anders, Florian; Petry, Simon; Witte, Felix; Lokstein, Heiko

doi:10.1016/j.chemphys.2022.111517

Cited by 12 publications

(33 citation statements)

References 56 publications

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“…The emission spectrum of Crt S 2 is experimentally and theoretically known (Table 1). 7 It should however be noted that the experimental 0-0 excitation energies of Crts, typically listed at around 500 nm for the Crts discussed here, 1 do not correspond to the FRET-relevant emission energies. Instead, the overall emission spectrum is relevant, not the energetic location of individual Franck-Condon factors such as for the 0-0 transition or a maximum intensity.…”

Section: Resultsmentioning

confidence: 71%

“…While the adiabatic transition may be important for the photophysical characterization of the Crts, the mean of the Crt emission spectra is not at all located close to 0-0. 7 The general depiction of S 2 being energetically far from the Chl Q states is thus very misleading in terms of Crt-Chl FRET capabilities.…”

Section: Resultsmentioning

confidence: 99%

“…The orientation factors κ 2 for the chromophores and states in the CP29 model were derived from TDMs that approximately correspond to high-level quantum mechanics calculations. 7,45 Namely, the Chl Q band TDM was associated to the Qy state and the B band TDM to the B x state, aligned along the Chl atoms NB-ND and C4A-C4C, respectively. For Crts S 2 states, TDMs were aligned along the axis connecting the C12 and C32 atoms (exception: Bcr, C12 and C19 atoms due to different atom numbering; same physical representation).…”

Section: Methodsmentioning

confidence: 99%

“…It has been known for a long time that the vibrational relaxation (VR) of the strongly absorbing Crt state (S 2 ) is very fast (sub-100 fs 18 ) and the actual reorganization energy of this process is large for such small changes in molecular geometry. 7,19,20 Despite detectable S 2 emissions of certain Crts, EET processes in plants between Crts and Chls have, to our knowledge, not been attributed to FRET (although shown for bacteriochlorophylls almost 30 years ago 21 ). It is well-established that most of the (weak) fluorescence of Crts arises from S 2 , not S 1 .…”

Section: Introductionmentioning

confidence: 91%

“…Instead, Crts in most organisms containing Chl a/b exhibit strong absorption and significant overlap with the higher energy Chl bands. Notably, the Chl B band consists of multiple states 7 . For the sake of simplicity, they are treated as a single entity in the following.…”

Section: Introductionmentioning

confidence: 99%

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Excitation energy transfer between higher excited states of photosynthetic pigments: 1. Carotenoids facilitate B → Q band conversion in chlorophylls

Götze

Lokstein

2023

Preprint

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Chlorophylls (Chls) are known for fast, sub-picosecond internal conversion (IC) from ultraviolet/blue absorb-ing ("B" or "Soret" states) to the energetically lower, red light-absorbing Q states. Consequently, excitation energy transfer (EET) in photosynthetic pigment-protein complexes involving the B states has so far not been considered. We present, for the first time, a theoretical framework for the existence of B-B EET in tightly coupled Chl aggregates, such as photosynthetic pigment-protein complexes. We show that according to a simple Förster resonance energy transport (FRET) scheme, unmodulated B-B EET likely poses an existential threat, in particular the photochemical reaction centers (RCs). This insight leads to so-far undescribed roles for carotenoids (Crts, this article) and Chl b (next article in this series) of possibly primary importance. Here we show that B → Q IC is assisted by the symmetry-allowed Crt state (S2) by using the plant antenna complex CP29 as a model: The sequence is B → S2 (Crt, unrelaxed) →S2 (Crt, relaxed) → Q. This sequence has the advantage of preventing ~ 39% of Chl-Chl B-B EET, since the Crt S2 state is a highly efficient FRET acceptor. The likelihood of CP29 to forward potentially harmful B excitations towards the photosynthetic reaction center (RC) is thus reduced. In contrast to the B band of Chls, most Crt energy donation is energetically located near the Q band, which allows for 74/80% backdonation (from lutein/violaxanthin) to Chls. Neoxanthin, on the other hand, likely donates in the B band region of Chl b, with 76% efficiency. The latter is discussed in more detail in the next article in this series. Crts thus do not only act in their currently proposed photoprotective roles, but also as a crucial building block for any system that could otherwise deliver harmful "blue" excitations to the RCs.

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Section: Resultsmentioning

confidence: 71%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Excitation energy transfer between higher excited states of photosynthetic pigments: 1. Carotenoids facilitate B → Q band conversion in chlorophylls

Götze

Lokstein

2023

Preprint

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Exciton interactions of chlorophyll tetramer in water-soluble chlorophyll-binding protein BoWSCP

Cherepanov,

Milanovsky,

Neverov

et al. 2024

Spectrochimica Acta Part A: Molecular and Biomolecular Spectros

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Combined Multireference–Multiscale Approach to the Description of Photosynthetic Reaction Centers

Drosou,

Bhattacharjee,

Pantazis

2024

J. Chem. Theory Comput.

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A first-principles description of the primary photochemical processes that drive photosynthesis and sustain life on our planet remains one of the grand challenges of modern science. Recent research established that explicit incorporation of protein electrostatics in excited-state calculations of photosynthetic pigments, achieved for example with quantum–mechanics/molecular–mechanics (QM/MM) approaches, is essential for a meaningful description of the properties and function of pigment–protein complexes. Although time-dependent density functional theory has been used productively so far in QM/MM approaches for the study of such systems, this methodology has limitations. Here we pursue for the first time a QM/MM description of the reaction center in the principal enzyme of oxygenic photosynthesis, Photosystem II, using multireference wave function theory for the high-level QM region. We identify best practices and establish guidelines regarding the rational choice of active space and appropriate state-averaging for the efficient and reliable use of complete active space self-consistent field (CASSCF) and the N-electron valence state perturbation theory (NEVPT2) in the prediction of low-lying excited states of chlorophyll and pheophytin pigments. Given that the Gouterman orbitals are inadequate as a minimal active space, we define specific minimal and extended active spaces for the NEVPT2 description of electronic states that fall within the Q and B bands. Subsequently, we apply our multireference–QM/MM protocol to the description of all pigments in the reaction center of Photosystem II. The calculations reproduce the electrochromic shifts induced by the protein matrix and the ordering of site energies consistent with the identity of the primary donor (ChlD1) and the experimentally known asymmetric and directional electron transfer. The optimized protocol sets the stage for future multireference treatments of multiple pigments, and hence for multireference studies of charge separation, while it is transferable to the study of any photoactive embedded tetrapyrrole system.

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Spectral characterization of the main pigments in the plant photosynthetic apparatus by theory and experiment

Cited by 12 publications

References 56 publications

Excitation energy transfer between higher excited states of photosynthetic pigments: 1. Carotenoids facilitate B → Q band conversion in chlorophylls

Excitation energy transfer between higher excited states of photosynthetic pigments: 1. Carotenoids facilitate B → Q band conversion in chlorophylls

Exciton interactions of chlorophyll tetramer in water-soluble chlorophyll-binding protein BoWSCP

Combined Multireference–Multiscale Approach to the Description of Photosynthetic Reaction Centers

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