Effects of trypsin and bivalent cations on P-680+-reduction,fluorescence induction and oxygen evolution in Photosystem II membrane fragments from spinach |
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| Institution: | 1. Science and Technology Application and Research Center, Siirt University, Siirt, 56100, Turkey;2. Department of Chemistry, Faculty of Science, University of Dicle, 21280, Diyarbakir, Turkey;3. Science and Technology Application and Research Center (DUBTAM), Dicle University, Diyarbakir, 21280, Turkey;4. Department of Chemical Engineering, Kazakh-British Technical University, 050000, Almaty, Kazakhstan;5. Department of Chemical Technology, Institute of Chemical Engineering, Kazakh National Research Technical University After K. I. Satpayev, 050000 Almaty, Kazakhstan;6. Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Dicle University, Diyarbakir, 21280, Turkey;1. Department of Chemistry, Shantou University, No.243 University Road, Shantou, Guangdong, 515063, PR China;2. School of Optoelectronic Information, University of Electronic Science and Technology of China (UESTC), Chengdu, 610054, PR China;1. Department of Chemistry, Faculty of Science, University of Dicle, 21280 Diyarbakir, Turkey;2. ??rnak University, Department of Field Crops, Faculty of Agriculture, ??rnak 73000, Turkey;3. Kazakh-British Technical University, School of Chemical Engineering, Almaty, Kazakhstan;4. Satbayev University, Institute of Chemical and Biological Technologies, Almaty, Kazakhstan;1. School of Energy Source and Mechanical Engineering, Shanghai University of Electric Power, Shanghai, 200090, PR China;2. Shanghai Engineering Research Center of Power Generation Environment Protection, Shanghai, 200090, PR China;3. Shanghai Institute of Pollution Control and Ecological Security, Shanghai, 200092, PR China;1. Department of Physics and Astronomy, Purdue University, 525 Northwestern Avenue, West Lafayette, IN 47907, United States;2. Department of Chemistry, University of Houston, Houston, TX 77204-5003, United States |
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| Abstract: | Laser-flash-induced absorption changes at 830 nm, fluorescence-induction curves and the average oxygen yield per flash have been measured in spinach Photosystem II membrane fragments as a function of trypsin treatment and its modification by CaCl2. The following was found. (i) The relative contribution of the nanosecond relaxation to the overall decay kinetics of 830 nm absorption changes reflecting the P-680+-reduction decreases as a function of incubation time with trypsin. Simultaneously, mild treatment at pH = 6.0 markedly increases the extent of 200 μs kinetics that highly revert back to nanosecond kinetics by CaCl2 addition. After harsher trypsin treatment (pH = 7.5) pH-dependent 2–20 μs kinetics appear that cannot be reverted to nanosecond kinetics by CaCl2. (ii) The CaCl2-induced restoration of nanosecond kinetics is mainly due to a Ca2+-induced effect rather than to a functional role of Cl?. Sr2+ can substantially substitute for Ca2+, whereas Mg2+, Mn2+ and monovalent ions are almost inefficient. (iii) A quantitative correlation between the extent of the nanosecond kinetics and the average oxygen yield per flash was not observed. (iv) If CaCl2 is present in the assay medium for trypsin treatment the samples are markedly protected to proteolytic degradation. This effect mainly refers to the reaction pattern of the acceptor side. Other bivalent cations can substitute Ca2+ for its protective function. (v) The CaCl2-induced protection to proteolytic attack is extremely sensitive to a very short trypsin pretreatment that does hardly affect the shape of the fluorescence induction curve. The results are discussed in relation to the functional and structural organization of Photosystem II. |
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