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Reactions on Polymers
Published in Charles E. Carraher, Carraher's Polymer Chemistry, 2017
A special BCHl (P870) pair is excited either by the absorption of a photon or by acquiring this excitation energy from an energy transfer from the peripheral antenna BCHl (not shown for simplicity) triggering a photoinduced electron transfer inside the RC (36). Two photoinduced electrons are transferred to a plastoquinone located inside the photosynthesis membrane. This plastoquinone acts as an electron acceptor and is consequently reduced to a semiquinone and finally to a hydroquinone. This reduction involves the uptake of two protons from water on the internal cytoplasmic side of the membrane. This hydroquinone then diffuses to the next component of the apparatus, a proton pump called the cytochrome bc1 complex.
Interfacial Catalysis at Oil/Water Interfaces
Published in Alexander G. Vdlkdv, Interfacial Catalysis, 2002
Manganese-binding centers were first revealed in thylakoid membranes by EPR methods, and it is now understood that four manganese ions are necessary for oxygen evolution during water photo-oxidation. Plastoquinone (PQ) acts as a transmembrane carrier of electrons and protons between reaction centers of two photosystems in the case of noncyclic electron transfer and may also serve as a molecular “tumbler” that switches between one-electron reactions and two-electron reactions. Pheophytin is an intermediate acceptor in PS II. Direct formation of P680 pheophytin ion radical pairs was revealed by experiments on magnetic interactions between pheophytin and PQ reflected in the EPR spectra.
Non-stomatal limitation of photosynthesis by soil salinity
Published in Critical Reviews in Environmental Science and Technology, 2021
Ting Pan, Minmin Liu, Vladimir D. Kreslavski, Sergey K. Zharmukhamedov, Chenrong Nie, Min Yu, Vladimir V. Kuznetsov, Suleyman I. Allakhverdiev, Sergey Shabala
It was shown that maintaining a high photosynthetic electron transport and thylakoid membrane structure under strong light + salt conditions needs optimal photosystem stoichiometry and conservation of the plastiquinone pool able to support effective electron transfer (Ksas et al., 2018; Stefanov et al., 2018; Tu et al., 2012). Here, the enhanced phototolerance of the plants is directly related to their elevated capacities for plastoquinone biosynthesis plastoquinone not only for photosystem II but also stored in lipid droplets associated with the thylakoid membranes (the plastoglobules) (Pralon et al., 2019). An enhanced cyclic electron transport and dark respiration could be another protective mechanism (Kreslavski, Carpentier, Klimov, Murata, & Allakhverdiev, 2007; Yamori & Shikanai, 2016).