scholarly journals Trimeric Photosystem I facilitates energy transfer from phycobilisomes in Synechocystis PCC 6803

2021 ◽  
Author(s):  
Parveen Akhtar ◽  
Avratanu Biswas ◽  
Fanny Balog-Vig ◽  
Ildiko Domonkos ◽  
László Kovács ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Light Harvesting ◽  
Excitation Energy Transfer ◽  
State Transitions ◽  
Synechocystis Pcc 6803 ◽  
Light Harvesting Complexes ◽  
Time Resolved ◽  
Cyanobacterial Species ◽  
In Cells ◽  
Pcc 6803

In cyanobacteria, phycobilisomes serve as peripheral light-harvesting complexes of the two photosystems, extending their antenna size and the wavelength range of photons available for photosynthesis. The abundance of phycobilisomes, the number of phycobiliproteins they contain, and their light-harvesting function are dynamically adjusted in response to the physiological conditions. Phycobilisomes are also thought to be involved in state transitions that maintain the excitation balance between the two photosystems. Unlike its eukaryotic counterpart, PSI is trimeric in many cyanobacterial species and the physiological significance of this is not well understood. Here we compared the composition and light-harvesting function of phycobilisomes in cells of Synechocystis PCC 6803, which has primarily trimeric PSI, and the ?psaL mutant unable to form trimers. We also investigated a mutant additionally lacking the PsaJ and PsaF subunits of PSI, as PsaF has been proposed to facilitate interaction with phycobilisomes. Both strains with monomeric PSI accumulated significantly less phycocyanin (which constitutes the phycobilisome rods) per chlorophyll, while the allophycocyanin content was unchanged compared to WT. These data show that cells with monomeric PSI have higher abundance of smaller phycobilisomes. Steady-state and time-resolved fluorescence spectroscopy at room temperature and 77 K revealed that PSII receives more energy from the phycobilisomes at the expense of PSI in cells with monomeric PSI, regardless of the presence of PsaF. Taken together, these results show that the trimeric organization of PSI is advantageous for efficient and balanced excitation energy transfer from phycobilisomes in Synechocystis.

Variety, the spice of life and essential for robustness in excitation energy transfer in light-harvesting complexes

2020 ◽  
Vol 221 ◽  
pp. 59-76 ◽  
Author(s):  
Sue Ann Oh ◽  
David F. Coker ◽  
David A. W. Hutchinson
Keyword(s):  
Energy Transfer ◽  
Excitation Energy ◽  
Recent Work ◽  
Energy Transport ◽  
Light Harvesting ◽  
Excitation Energy Transfer ◽  
Light Harvesting Complexes ◽  
Protein Scaffold ◽  
Site Variation

We review our recent work showing how important the site-to-site variation in coupling between chloroplasts in FMO and their protein scaffold environment is for energy transport in FMO and investigate the role of vibronic modes in this transport.

scholarly journals Predicting the future of excitation energy transfer in light-harvesting complex with artificial intelligence-based quantum dynamics

2021 ◽  
Author(s):  
Arif Ullah ◽  
Pavlo O. Dral
Keyword(s):  
Artificial Intelligence ◽  
Energy Transfer ◽  
Excitation Energy ◽  
Quantum Dynamics ◽  
Light Harvesting ◽  
Computational Cost ◽  
Excitation Energy Transfer ◽  
Reorganization Energy ◽  
Quantum Effects ◽  
Light Harvesting Complexes

Exploring excitation energy transfer (EET) in light-harvesting complexes (LHCs) is essential for understanding the natural processes and design of highly-efficient photovoltaic devices. LHCs are open systems, where quantum effects may play a crucial role for almost perfect utilization of solar energy. Simulation of energy transfer with inclusion of quantum effects can be done within the framework of dissipative quantum dynamics (QD), which are computationally expensive. Thus, artificial intelligence (AI) offers itself as a tool for reducing the computational cost. We suggest AI-QD approach using AI to directly predict QD as a function of time and other parameters such as temperature, reorganization energy, etc., completely circumventing the need of recursive step-wise dynamics propagation in contrast to the traditional QD and alternative, recursive AI-based QD approaches. Our trajectory-learning AI-QD approach is able to predict the correct asymptotic behavior of QD at infinite time. We demonstrate AI-QD on seven-sites Fenna–Matthews–Olson (FMO) complex.

scholarly journals Strategies to enhance the excitation energy-transfer efficiency in a light-harvesting system using the intra-molecular charge transfer character of carotenoids

2017 ◽  
Vol 198 ◽  
pp. 59-71 ◽  
Author(s):  
Nao Yukihira ◽  
Yuko Sugai ◽  
Masazumi Fujiwara ◽  
Daisuke Kosumi ◽  
Masahiko Iha ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Charge Transfer ◽  
Excitation Energy ◽  
Brown Algae ◽  
Light Harvesting ◽  
Excitation Energy Transfer ◽  
Light Harvesting Complexes ◽  
Light Harvesting Complex ◽  
Molecular Charge ◽  
Intra Molecular Charge Transfer

Fucoxanthin is a carotenoid that is mainly found in light-harvesting complexes from brown algae and diatoms. Due to the presence of a carbonyl group attached to polyene chains in polar environments, excitation produces an excited intra-molecular charge transfer. This intra-molecular charge transfer state plays a key role in the highly efficient (∼95%) energy-transfer from fucoxanthin to chlorophyllain the light-harvesting complexes from brown algae. In purple bacterial light-harvesting systems the efficiency of excitation energy-transfer from carotenoids to bacteriochlorophylls depends on the extent of conjugation of the carotenoids. In this study we were successful, for the first time, in incorporating fucoxanthin into a light-harvesting complex 1 from the purple photosynthetic bacterium,Rhodospirillum rubrumG9+ (a carotenoidless strain). Femtosecond pump-probe spectroscopy was applied to this reconstituted light-harvesting complex in order to determine the efficiency of excitation energy-transfer from fucoxanthin to bacteriochlorophyllawhen they are bound to the light-harvesting 1 apo-proteins.

scholarly journals Excitation energy transfer kinetics of trimeric, monomeric and subunit-depleted Photosystem I from Synechocystis PCC 6803

2021 ◽  
Vol 478 (7) ◽  
pp. 1333-1346
Author(s):  
Parveen Akhtar ◽  
Avratanu Biswas ◽  
László Kovács ◽  
Nathan Nelson ◽  
Petar H. Lambrev
Keyword(s):  
Energy Transfer ◽  
Excitation Energy ◽  
Photosystem I ◽  
Energy State ◽  
Excitation Energy Transfer ◽  
Intermediate Energy ◽  
Reaction Centre ◽  
Synechocystis Pcc 6803 ◽  
Monomeric Complex ◽  
Pcc 6803

Photosystem I is the most efficient photosynthetic enzyme with structure and composition highly conserved among all oxygenic phototrophs. Cyanobacterial Photosystem I is typically associated into trimers for reasons that are still debated. Almost universally, Photosystem I contains a number of long-wavelength-absorbing ‘red’ chlorophylls (Chls), that have a sizeable effect on the excitation energy transfer and trapping. Here we present spectroscopic comparison of trimeric Photosystem I from Synechocystis PCC 6803 with a monomeric complex from the ΔpsaL mutant and a ‘minimal’ monomeric complex ΔFIJL, containing only subunits A, B, C, D, E, K and M. The quantum yield of photochemistry at room temperature was the same in all complexes, demonstrating the functional robustness of this photosystem. The monomeric complexes had a reduced far-red absorption and emission equivalent to the loss of 1.5–2 red Chls emitting at 710–715 nm, whereas the longest-wavelength emission at 722 nm was not affected. The picosecond fluorescence kinetics at 77 K showed spectrally and kinetically distinct red Chls in all complexes and equilibration times of up to 50 ps. We found that the red Chls are not irreversible traps at 77 K but can still transfer excitations to the reaction centre, especially in the trimeric complexes. Structure-based Förster energy transfer calculations support the assignment of the lowest-energy state to the Chl pair B37/B38 and the trimer-specific red Chl emission to Chls A32/B7 located at the monomer–monomer interface. These intermediate-energy red Chls facilitate energy migration from the lowest-energy states to the reaction centre.

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