Triplet state quenching of bacteriochlorophyll c aggregates in a protein-free environment of a chlorosome interior

Vinklárek, Ivo S.; Bína, David; Malina, Tomáš; Collins, Aaron M.; Litvín, Radek; Alster, Jan; Pšenčı́k, Jakub

doi:10.1016/j.chemphys.2019.110542

Cited by 6 publications

(13 citation statements)

References 42 publications

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“…This seems to constitute a novel mode of photoprotection of photosynthetic pigments, in addition to already known photoprotective mechanisms, i.e., (1) quenching of Chl triplet states by carotenoids; (2) quenching of Chl singlet states by carotenoids. (e.g., 18); and (3) shortening of the excited state lifetimes of pigments by aggregation. , Our results further corroborate the previously proposed function of OHP1/2 as a pigment delivery (and/or storage) protein, which would require effective protection of the attached pigments from photooxidation.…”

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confidence: 88%

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Photoprotection of Photosynthetic Pigments in Plant One-Helix Protein 1/2 Heterodimers

Pšenčı́k

Hey

Grimm

et al. 2020

J. Phys. Chem. Lett.

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One-helix proteins 1 and 2 (OHP1/2) are members of the family of light-harvesting-like proteins (LIL) in plants, and their potential function(s) have been initially analyzed only recently. OHP1 and OHP2 are structurally related to the transmembrane α-helices 1 and 3 of all members of the light-harvesting complex (LHC) superfamily. Arabidopsis thaliana OHPs form heterodimers which bind 6 chlorophylls (Chls) a and two carotenoids in vitro. Their function remains unclear, and therefore, a spectroscopic study with reconstituted OHP1/OHP2-complexes was performed. Steady-state spectroscopy did not indicate singlet excitation energy transfer between pigments. Thus, a light-harvesting function can be excluded. Possible pigment-storage and/or -delivery functions of OHPs require photoprotection of the bound Chls. Hence, Chl and carotenoid triplet formation and decays in reconstituted OHP1/2 dimers were measured using nanosecond transient absorption spectroscopy. Unlike in all other photosynthetic LHCs, unquenched Chl triplets were observed with unusually long lifetimes. Moreover, there were virtually no differences in both Chl and carotenoid triplet state lifetimes under either aerobic or anaerobic conditions. The results indicate that both Chls and carotenoids are shielded by the proteins from interactions with ambient oxygen and, thus, protected against formation of singlet oxygen. Only a minor portion of the Chl triplets was quenched by carotenoids. These results are in stark contrast to all previously observed photoprotective processes in LHC/LIL proteins and, thus, may constitute a novel mechanism of photoprotection in the plant photosynthetic apparatus.

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supporting

confidence: 88%

“…(3) shortening of the excited state lifetimes of pigments by aggregation. 37,38 Our results further corroborate the previously proposed function of OHP1/2 as a pigment delivery (and/or storage) protein, which would require effective protection of the attached pigments from photooxidation.…”

mentioning

confidence: 99%

Photoprotection of Photosynthetic Pigments in Plant One-Helix Protein 1/2 Heterodimers

Pšenčı́k

Hey

Grimm

et al. 2020

J. Phys. Chem. Lett.

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“…tepidum and Cfl. aurantiacus J-10-fl cells were grown as described previously 24 , 33 and chlorosomes were purified by ultracentrifugation using two sucrose gradients 40 . BChl c was isolated from Cba.…”

Section: Methodsmentioning

confidence: 99%

“…The second method is based on solvent exchange caused by slow addition of the buffer into the pigment mixture, this time both pigments dissolved in THF together with a block copolymer poly(butadiene-b-ethylene oxide) as described in ref. 34 with modifications 24 . This method is referred to as the "slow" method.…”

Section: Methodsmentioning

confidence: 99%

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Superradiance of bacteriochlorophyll c aggregates in chlorosomes of green photosynthetic bacteria

Malina

Koehorst

Bína

et al. 2021

Sci Rep

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Chlorosomes are the main light-harvesting complexes of green photosynthetic bacteria that are adapted to a phototrophic life at low-light conditions. They contain a large number of bacteriochlorophyll c, d, or e molecules organized in self-assembling aggregates. Tight packing of the pigments results in strong excitonic interactions between the monomers, which leads to a redshift of the absorption spectra and excitation delocalization. Due to the large amount of disorder present in chlorosomes, the extent of delocalization is limited and further decreases in time after excitation. In this work we address the question whether the excitonic interactions between the bacteriochlorophyll c molecules are strong enough to maintain some extent of delocalization even after exciton relaxation. That would manifest itself by collective spontaneous emission, so-called superradiance. We show that despite a very low fluorescence quantum yield and short excited state lifetime, both caused by the aggregation, chlorosomes indeed exhibit superradiance. The emission occurs from states delocalized over at least two molecules. In other words, the dipole strength of the emissive states is larger than for a bacteriochlorophyll c monomer. This represents an important functional mechanism increasing the probability of excitation energy transfer that is vital at low-light conditions. Similar behaviour was observed also in one type of artificial aggregates, and this may be beneficial for their potential use in artificial photosynthesis.

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Utilization of blue-green light by chlorosomes from the photosynthetic bacterium Chloroflexus aurantiacus: Ultrafast excitation energy conversion and transfer

Yakovlev¹,

Taisova²,

Fetisova³

2021

Biochimica et Biophysica Acta (BBA) - Bioenergetics

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Triplet state quenching of bacteriochlorophyll c aggregates in a protein-free environment of a chlorosome interior

Cited by 6 publications

References 42 publications

Photoprotection of Photosynthetic Pigments in Plant One-Helix Protein 1/2 Heterodimers

Photoprotection of Photosynthetic Pigments in Plant One-Helix Protein 1/2 Heterodimers

Superradiance of bacteriochlorophyll c aggregates in chlorosomes of green photosynthetic bacteria

Utilization of blue-green light by chlorosomes from the photosynthetic bacterium Chloroflexus aurantiacus: Ultrafast excitation energy conversion and transfer

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