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1996 (1)
1Author    L. Kovács3, U. Hegdeb, S. Padhyeb, G. Bernät3, S. Demeter3Requires cookie*
 Title    Effects of Potassium-(picrate)-(18-crown-6) on the Photosynthetic Electron Transport  
 Abstract    The effects of potassium-(picrate)-(18-crown-6) on the electron transport of photosystem II was investigated in isolated pea thylakoids. Low concentrations of the compound inhibited the fast decay of fluorescence yield associated with electron transfer between the primary (Q a) and secondary (Q b) quinone electron acceptor and increased the intermediary level of fluorescence to the Fmax level. The decay half-time of fluorescence yield measured in the presence of D C M U (S2Q A' charge recombination) decreased from about 1.8 s to about 0.3 s in thylakoids treated with potassium-(picrate)-(18-crown-6). W hile the inhibition of electron transport by D C M U gave rise to the appearance of a thermoluminescence band at about + 10°C (S2Q A~charge recombination) addition of potassium-(picrate)-(18-crown-6) resulted in a thermoluminescence band at about -10°C. Increasing concentrations of potassium-(picrate)-(18-crown-6) diminished the fluorescence yield and the -10°C TL band and abolished the Signal II S and Signal I I f E P R signals of the tyrosine-D and tyrosine-Z electron donors, respec­ tively. The phenolic-type inhibitor, potassium picrate had the same effect on thermolumines­ cence and on the tyrosine E P R signals. It is concluded that potassium-(picrate)-(18-crown-6) is a phenolic type inhibitor owing to its picrate constituent. A t low concentrations picrate and potassium-(picrate)-18-crown) not only block the electron transport between Q A and O b but they probably decrease the midpoint redox potential of Q A, as well. A t high concen­ trations they also inhibit the light-induced oxidation of the tyrosine-D and tyrosine-Z donors. 
  Reference    Z. Naturforsch. 51c, 539—547 (1996); received December 22 1995/ 
  Published    1996 
  Keywords    Phenolic Inhibitors, Photosynthesis, Photosystem II, Thermoluminescence, Electron Paramagnetic Resonance 
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 TEI-XML for    default:Reihe_C/51/ZNC-1996-51c-0539.pdf 
 Identifier    ZNC-1996-51c-0539 
 Volume    51