The entanglement of excitation energy transfer and electron transfer in the reaction centre of photosystem II

1998 ◽  
Vol 356 (1736) ◽  
pp. 449-464 ◽  
Author(s):  
David R. Klug ◽  
James R. Durrant ◽  
James Barber
Keyword(s):  
Electron Transfer ◽  
Energy Transfer ◽  
Photosystem Ii ◽  
Excitation Energy ◽  
Excitation Energy Transfer ◽  
Reaction Centre

Cerulenin-Induced Modifications in the Fatty Acid Composition Affect Excitation Energy Transfer in Thylakoids of Petunia hybrida Leaves

1988 ◽  
Vol 43 (5-6) ◽  
pp. 431-437 ◽  
Author(s):  
Josef A. Graf ◽  
Karin Witzan ◽  
Reto J. Strasser
Keyword(s):  
Fatty Acid Composition ◽  
Energy Transfer ◽  
Fatty Acid ◽  
Photosystem Ii ◽  
Energy Distribution ◽  
Excitation Energy ◽  
Acid Composition ◽  
Petunia Hybrida ◽  
Excitation Energy Transfer ◽  
Acyl Lipids

Cerulenin-induced modifications in the fatty acid composition have been used to investigate the influence of acyl lipids on excitation energy distribution in thylakoid membranes of Petunia hybrida by means of 77 K fluorescence spectroscopy. Although cerulenin has no effect on relative contents of chlorophyll and acyl lipids, changes in the fatty acid composition of all thylakoid acyl lipids have been observed. The main cerulenin effect seems to be an increase in linoleic acid at the expense of saturated and monounsaturated C16- and C18-fatty acids resulting most likely in an increase in acyl lipid species containing both linoleic and linolenic acid. Low temperature (77 K ) fluorescence kinetics reveal a remarkable decrease in the ratio of the variable divided by the maximal fluorescence of photosystem II (F2(v)/F2(M)), taken as indicator for cerulenin-induced changes in this photosystem. Calculations of the excitation energy distribution terms based on a grouped bipartite model of photosynthesis suggest that a decrease in this ratio is caused by changes in energy transfer probabilities responsible for both, photochemical trapping of photosystem II and energetic cooperativity (grouping) between different photosystem II-light harvesting complex-units. Moreover, changes in the conformation responsible for spillover energy transfer are most likely to occur. Correlations between cerulenin-induced modifications of fatty acid composition and energy distribution support the assumption that excitation energy transfer depends on the structural state of the lipid matrix.

scholarly journals Excitation Energy Transfer and Charge Separation in Photosystem II Membranes Revisited

2006 ◽  
Vol 91 (10) ◽  
pp. 3776-3786 ◽  
Author(s):  
Koen Broess ◽  
Gediminas Trinkunas ◽  
Chantal D. van der Weij-de Wit ◽  
Jan P. Dekker ◽  
Arie van Hoek ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Photosystem Ii ◽  
Excitation Energy ◽  
Charge Separation ◽  
Excitation Energy Transfer

scholarly journals What is β–carotene doing in the photosystem II reaction centre?

2002 ◽  
Vol 357 (1426) ◽  
pp. 1431-1440 ◽  
Author(s):  
Alison Telfer
Keyword(s):  
Electron Transfer ◽  
Photosystem Ii ◽  
Excitation Energy ◽  
Triplet State ◽  
Singlet Oxygen ◽  
Spin Exchange ◽  
Primary Electron ◽  
Triplet States ◽  
Reaction Centre ◽  
Β Carotene

During photosynthesis carotenoids normally serve as antenna pigments, transferring singlet excitation energy to chlorophyll, and preventing singlet oxygen production from chlorophyll triplet states, by rapid spin exchange and decay of the carotenoid triplet to the ground state. The presence of two β–carotene molecules in the photosystem II reaction centre (RC) now seems well established, but they do not quench the triplet state of the primary electron–donor chlorophylls, which are known as P 680 . The β–carotenes cannot be close enough to P 680 for triplet quenching because that would also allow extremely fast electron transfer from β–carotene to P + 680 , preventing the oxidation of water. Their transfer of excitation energy to chlorophyll, though not very efficient, indicates close proximity to the chlorophylls ligated by histidine 118 towards the periphery of the two main RC polypeptides. The primary function of the β–carotenes is probably the quenching of singlet oxygen produced after charge recombination to the triplet state of P 680 . Only when electron donation from water is disturbed does β–carotene become oxidized. One β–carotene can mediate cyclic electron transfer via cytochrome b 559. The other is probably destroyed upon oxidation, which might trigger a breakdown of the polypeptide that binds the cofactors that carry out charge separation.

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