Energy transfer to the reaction centres in bacterial photosynthesis

1972 ◽  
Vol 3 (6) ◽  
pp. 515-523 ◽  
Author(s):  
A. Yu. Borisov ◽  
V. I. Godik
Keyword(s):  
Energy Transfer ◽  
Bacterial Photosynthesis ◽  
Reaction Centres

scholarly journals How carotenoids protect bacterial photosynthesis

2000 ◽  
Vol 355 (1402) ◽  
pp. 1345-1349 ◽  
Author(s):  
Richard J. Cogdell ◽  
Tina D. Howard ◽  
Robert Bittl ◽  
Erberhard Schlodder ◽  
Irene Geisenheimer ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Photosynthetic Bacteria ◽  
Bacterial Photosynthesis ◽  
Specific Reference ◽  
Structural Studies ◽  
Triplet Energy ◽  
Purple Photosynthetic Bacteria ◽  
Reaction Centres ◽  
Essential Function ◽  
Triplet Energy Transfer

The essential function of carotenoids in photosynthesis is to act as photoprotective agents, preventing chlorophylls and bacteriochlorophylls from sensitizing harmful photodestructive reactions in the presence of oxygen. Based upon recent structural studies on reaction centres and antenna complexes from purple photosynthetic bacteria, the detailed organization of the carotenoids is described. Then with specific reference to bacterial antenna complexes the details of the photoprotective role, triplet–triplet energy transfer, are presented.

The pigment antenna constraining the light reactions: photosynthetic energy redistribution indicated by leaf absorbance changes

2020 ◽  
Author(s):  
Shari Van Wittenberghe ◽  
Valero Laparra ◽  
Nacho Ignacio Garcia ◽  
Luis Alonso ◽  
Beatriz Fernandez Marín ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Energy Transfer ◽  
Remote Sensing Data ◽  
Energy Regulation ◽  
Energy Redistribution ◽  
Chl A ◽  
Sensing Data ◽  
Reaction Centres ◽  
Chl A Fluorescence ◽  
Absorbance Changes

<p>The solar energy absorbed by the vegetation light-harvesting antenna complexes supplies the photosynthetic light reactions with a highly efficient transfer of quantum energy. The absorbed energy is efficiently transferred from one molecule to another, until being used by the reaction centres for the further carbon reactions. The energy transfer to the reaction centres is hereby highly regulated by the variable aggregation of pigments in the antenna complexes, allowing for quick and slower adjustments according to the incoming solar radiance. To control and protect the pigment antenna and the reaction centres from a potentially harmful solar radiance excess, these regulated photoprotective mechanisms are activated at different time scales at the antenna level, allowing vegetation to adapt to changing light conditions. The understanding of these energy regulative processes from optical measurements is essential in order to monitor plants' adaptation strategies to stressful environments and changing climates from remote sensing data.</p><p>Using high-spectral resolution leaf spectroscopy in a controlled laboratory set-up, we have observed detailed and significant absorbance shifts controlled by the pigment antennas themselves. Simultaneous measurements of both upward and downward spectrally-resolved leaf radiance (Lup(λ), Ldw(λ), W m<sup>-2</sup> sr<sup>-1</sup> nm<sup>-1</sup>) allowed us to observe the specific absorbance changes at leaf level, including changes in chlorophyll (Chl) a fluorescence emission (Fup(λ), Fdw(λ), W m<sup>-2</sup> sr<sup>-1</sup> nm<sup>-1</sup>). Interestingly, these changes due to shifts in energy redistribution were: 1) observed in the PAR region and even far beyond 700 nm, and 2) indicated a prominent role of both Carotenoid and Chl a molecules in the creation of alternative energy sinks, i.e. constraining the energy transfer to the reaction centres. Hereby, a significant redistribution of photosynthetic light energy was observed in the 500-800 nm range, highlighting this spectral region to be of potential interest for remote sensing. We further revealed that these energy redistributions do not necessary occur in parallel with Chl a fluorescence changes, illustrating the importance of different energy redistribution mechanisms constraining the photosynthetic light reactions. To conclude, a good quantitative understanding of all mechanisms of energy regulation in plants based on VIS-NIR wavelengths is essential 1) to be able to understand these trends using remote sensing data, 2) to better model the adaptations of vegetation to changing climate and environmental conditions, and 3) potentially better predict future trends in dynamic global vegetation models.</p>

Chlorophyll Spectral Heterogeneity and Energy Transfer to PSII Reaction Centres

1990 ◽  
pp. 1273-1276
Author(s):  
Flavio M. Garlaschi ◽  
Giuseppe Zucchelli ◽  
Robert C. Jennings
Keyword(s):  
Energy Transfer ◽  
Reaction Centres

Energy transfer in bacterial photosynthesis

1972 ◽  
Vol 3 (3-4) ◽  
pp. 211-220 ◽  
Author(s):  
A. Yu. Borisov ◽  
V. I. Godik
Keyword(s):  
Energy Transfer ◽  
Bacterial Photosynthesis

scholarly journals The structure of allophycocyanin B fromSynechocystisPCC 6803 reveals the structural basis for the extreme redshift of the terminal emitter in phycobilisomes

2014 ◽  
Vol 70 (10) ◽  
pp. 2558-2569 ◽  
Author(s):  
Pan-Pan Peng ◽  
Liang-Liang Dong ◽  
Ya-Fang Sun ◽  
Xiao-Li Zeng ◽  
Wen-Long Ding ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Excitation Energy ◽  
Fluorescence Emission ◽  
Structural Basis ◽  
Internal Cavity ◽  
Conjugation System ◽  
Photosynthetic Membrane ◽  
Light Harvesting Complexes ◽  
Α Subunit ◽  
Reaction Centres

Allophycocyanin B (AP-B) is one of the two terminal emitters in phycobilisomes, the unique light-harvesting complexes of cyanobacteria and red algae. Its low excitation-energy level and the correspondingly redshifted absorption and fluorescence emission play an important role in funnelling excitation energy from the hundreds of chromophores of the extramembraneous phycobilisome to the reaction centres within the photosynthetic membrane. In the absence of crystal structures of these low-abundance terminal emitters, the molecular basis for the extreme redshift and directional energy transfer is largely unknown. Here, the crystal structure of trimeric AP-B [(ApcD/ApcB)3] fromSynechocystissp. PCC 6803 at 1.75 Å resolution is reported. In the crystal lattice, eight trimers of AP-B form a porous, spherical, 48-subunit assembly of 193 Å in diameter with an internal cavity of 1.1 × 106 Å3. While the overall structure of trimeric AP-B is similar to those reported for many other phycobiliprotein trimers, the chromophore pocket of the α-subunit, ApcD, has more bulky residues that tightly pack the phycocyanobilin (PCB). Ring D of the chromophores is further stabilized by close interactions with ApcB from the adjacent monomer. The combined contributions from both subunits render the conjugated rings B, C and D of the PCB in ApcD almost perfectly coplanar. Together with mutagenesis data, it is proposed that the enhanced planarity effectively extends the conjugation system of PCB and leads to the redshifted absorption (λmax= 669 nm) and fluorescence emission (679 nm) of the ApcD chromophore in AP-B, thereby enabling highly efficient energy transfer from the phycobilisome core to the reaction centres.

Picosecond studies of primary charge separation in bacterial photosynthesis

1980 ◽  
Vol 298 (1439) ◽  
pp. 335-349 ◽  
Keyword(s):  
Charge Separation ◽  
Photosynthetic Bacteria ◽  
Chemical Potential ◽  
Picosecond Laser ◽  
Electronic Energy ◽  
Bacterial Photosynthesis ◽  
Reaction Centre ◽  
Primary Charge Separation ◽  
Reaction Centres ◽  
Primary Donor

With the aid of light and two coupled photosystems containing chlorophyll, green plants remove electrons from water, releasing O 2 , and convey them to CO 2 , reducing it to simple sugars and thence to carbohydrate. Photosynthetic bacteria operate more simply, employing a single photosystem. They reduce CO 2 but require substrates more easily oxidized than water, e.g. sulphide and succinate. Bacterial reaction centres free of the bulk chlorophyll that performs the light-harvesting function can be isolated. The reaction centre is the site where the electronic energy of the photoexcited molecule is converted to chemical potential. Thus bacterial reaction centres are ideal subjects for studying the details of this process by kinetic spectroscopy. Picosecond laser studies show that an electron is removed from the primary donor (a chlorophyll dimer) in 4ps or less and transferred in several stages to the ubiquinone acceptor in ca . 200 ps. Remarkably, reverse electron transfer is several orders of magnitude slower. The paper discusses how Nature may have accomplished this.

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