Abstract:When plants are exposed to high-light conditions, the potentially harmful excess energy is dissipated as heat, a process called non-photochemical quenching. Efficient energy dissipation can also be induced in the major light-harvesting complex of photosystem II (LHCII)
in vitro
, by altering the structure and interactions of several bound cofactors. In both cases, the extent of quenching has been correlated with conformational changes (twisting) affecting two bound carotenoids, neoxanthi… Show more
“…These two scenarios are difficult to distinguish because the LHCII(M) trimer cannot be easily purified. The assignment agrees with previous studies, suggesting that the energy equilibrations of LHCII and CP29 are changed depending upon the degree of aggregation. ,− The excitonic interactions between Chls in LHCII were found to be perturbed differently in various detergent solutions, and LHCII in a lipid system was determined to retain the most native state. , …”
supporting
confidence: 89%
“…Indeed, such a reductionistic picture may not be entirely adequate. It is known that spectroscopic signals, such as the excitonic circular dichroism spectra and fluorescence quantum yield, differ between LHCII samples in different environments , as well as different aggregates . On the other hand, the dynamics calculated from the LHCII X-ray structures are significantly slower than the decay of M–CP 2 (cf.…”
We measure the two-dimensional electronic spectra of the LHCII(M)− CP29−CP24 complex in photosystem II (PSII) and provide the first study of the ultrafast excitation energy transfer (EET) processes of an asymmetric and native lightharvesting assembly of the antenna of PSII. With comparisons to LHCII, we observe faster energy equilibrations in the intermediate levels of the LHCII(M)−CP29−CP24 complex at 662 and 670 nm. Notably, the putative "bottleneck" states in LHCII exhibit faster effective dynamics in the LHCII(M)−CP24−CP29 complex, with the average lifetime shortening from 2.5 ps in LHCII to 1.2 ps in the bigger assembly. The observations are supported by high-level structure-based calculations, and the accelerated dynamics can be attributed to the structural change of LHCII(M) in the bigger complex. This study shows that the biological functioning structures of the complexes are important to understand the overall EET dynamics of the PSII supercomplex.
“…These two scenarios are difficult to distinguish because the LHCII(M) trimer cannot be easily purified. The assignment agrees with previous studies, suggesting that the energy equilibrations of LHCII and CP29 are changed depending upon the degree of aggregation. ,− The excitonic interactions between Chls in LHCII were found to be perturbed differently in various detergent solutions, and LHCII in a lipid system was determined to retain the most native state. , …”
supporting
confidence: 89%
“…Indeed, such a reductionistic picture may not be entirely adequate. It is known that spectroscopic signals, such as the excitonic circular dichroism spectra and fluorescence quantum yield, differ between LHCII samples in different environments , as well as different aggregates . On the other hand, the dynamics calculated from the LHCII X-ray structures are significantly slower than the decay of M–CP 2 (cf.…”
We measure the two-dimensional electronic spectra of the LHCII(M)− CP29−CP24 complex in photosystem II (PSII) and provide the first study of the ultrafast excitation energy transfer (EET) processes of an asymmetric and native lightharvesting assembly of the antenna of PSII. With comparisons to LHCII, we observe faster energy equilibrations in the intermediate levels of the LHCII(M)−CP29−CP24 complex at 662 and 670 nm. Notably, the putative "bottleneck" states in LHCII exhibit faster effective dynamics in the LHCII(M)−CP24−CP29 complex, with the average lifetime shortening from 2.5 ps in LHCII to 1.2 ps in the bigger assembly. The observations are supported by high-level structure-based calculations, and the accelerated dynamics can be attributed to the structural change of LHCII(M) in the bigger complex. This study shows that the biological functioning structures of the complexes are important to understand the overall EET dynamics of the PSII supercomplex.
“…[29] Moreover,r edesigning and building more optimized non-photochemical quenching modules would also be an effective way to improve the efficiency of light energy utilization. [30] Compared to the yields of PHB produced from microorganisms, [31] our result was not high, and the molar conversion efficiencyofcarbon failed to reach 100 %. To solve these problems,i na ddition to enhance the stability of TMs,i ti sa lso necessary to improve the activity and the compatibility of TMs with the in vitro enzyme cascade.I mmobilization of enzymes and TMs on certain matrices,s uch as metal-organic frameworks,s ilica gel, and hydrogels,w ould be of benefit to the stability,a ctivity and reuse time.…”
Section: Phb Synthesis At High Substrate Concentrationmentioning
Many existing in vitro biosystems harness power from the chemical energy contained in substrates and cosubstrates,a nd light or electric energy provided from abiotic parts,l eading to ac ompromise in atom economy,i ncompatibility between biological and abiotic parts,a nd most importantly,incapability to spatiotemporally co-regenerate ATPand NADPH. In this study,w ed eveloped alight-powered in vitro biosystem for poly(3-hydroxybutyrate) (PHB) synthesis using natural thylakoid membranes (TMs) to regenerate ATPa nd NADPH for af ive-enzyme cascade.T hrough effective coupling of cofactor regeneration and mass conversion, 20 mM PHB was yielded from 50 mM sodium acetate with am olar conversion efficiency of carbon of 80.0 %a nd al ight-energy conversion efficiency of 3.04 %, whicha re muchh igher than the efficiencies of similar in vitro PHB synthesis biosystems. This suggests the promise of installing TMs as agreen engine to drive more enzyme cascades.
“…However, the formation of several other traps for the excess excitation energy cannot be excluded. For example, an orientational change of the neoxanthin carotenoid has been implicated in the switch to the dissipating conformation of LHCII, (Duffy et al 2014 ; Liguori et al 2015 ) that could take the role of the sensor, rather than a direct quencher (Li et al 2021 ). Fig.…”
Section: Zoom Into the Atomic Scale: The Quenching Sitementioning
The photosynthetic apparatus is a highly modular assembly of large pigment-binding proteins. Complexes called antennae can capture the sunlight and direct it from the periphery of two Photosystems (I, II) to the core reaction centers, where it is converted into chemical energy. The apparatus must cope with the natural light fluctuations that can become detrimental to the viability of the photosynthetic organism. Here we present an atomic scale view of the photoprotective mechanism that is activated on this line of defense by several photosynthetic organisms to avoid overexcitation upon excess illumination. We provide a complete macroscopic to microscopic picture with specific details on the conformations of the major antenna of Photosystem II that could be associated with the switch from the light-harvesting to the photoprotective state. This is achieved by combining insight from both experiments and all-atom simulations from our group and the literature in a perspective article.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
