Energetic Landscape and Terminal Emitters of Phycobilisome Cores from Quantum Chemical Modeling.

Autor: Cupellini L; Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via G. Moruzzi 13, 56124 Pisa, Italy., Gwizdala M; Department of Physics, University of Pretoria, Lynnwood Road, Pretoria 0002, South Africa.; Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Lynnwood Road, Pretoria 0002, South Africa., Krüger TPJ; Department of Physics, University of Pretoria, Lynnwood Road, Pretoria 0002, South Africa.; Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Lynnwood Road, Pretoria 0002, South Africa.; National Institute of Theoretical and Computational Sciences (NITheCS), https://nithecs.ac.za/.
Jazyk: angličtina
Zdroj: The journal of physical chemistry letters [J Phys Chem Lett] 2024 Sep 26; Vol. 15 (38), pp. 9746-9756. Date of Electronic Publication: 2024 Sep 17.
DOI: 10.1021/acs.jpclett.4c02005
Abstrakt: Phycobilisomes (PBs) are giant antenna supercomplexes of cyanobacteria that use phycobilin pigments to capture sunlight and transfer the collected energy to membrane-bound photosystems. In the PB core, phycobilins are bound to particular allophycocyanin (APC) proteins. Some phycobilins are thought to be terminal emitters (TEs) with red-shifted fluorescence. However, the precise identification of TEs is still under debate. In this work, we employ multiscale quantum-mechanical calculations to disentangle the excitation energy landscape of PB cores. Using the recent atomistic PB structures from Synechoccoccus PCC 7002 and Synechocystis PCC 6803, we compute the spectral properties of different APC trimers and assign the low-energy pigments. We show that the excitation energy of APC phycobilins is determined by geometric and electrostatic factors and is tuned by the specific protein-protein interactions within the core. Our findings challenge the simple picture of a few red-shifted bilins in the PB core and instead suggest that the red-shifts are established by the entire TE-containing APC trimers. Our work provides a theoretical microscopic basis for the interpretation of energy migration and time-resolved spectroscopy in phycobilisomes.
Databáze: MEDLINE
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