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1994 (1)
1976 (1)
1Author    Bernd Schmidt, HansJ. RurainskiRequires cookie*
 Title    Light-Dependent Interactions of Phenazine Methosulfate with 3-(3,4-Dichlorophenyl)-l,l-dimethylurea-Poisoned Chloroplasts  
 Abstract    The chlorophyll fluorescence of isolated chloroplasts in the presence of phenazine methosulfate (PMS) and 3-(3,4-dichlorophenyl)-l,l-dimethylurea (DCMU) can be quenched in a light-dependent reaction. This phenomenan has been studied and the following observations were made: 1. Quenching occurs under non-phosphorylating conditions and is stimulated by Mg2+ ions. 2. Under the same conditions, a light-dependent, Mg2+ stimulated transient decrease of absorp­ tion at 388 nm is observed which shows the spectral characteristics of PMS. 3. PMS is reversibly bound to chloroplasts. Under the experimental conditions used, binding amounts to as much as 0.5 mol PMS/mol chlorophyll. 4. Some uncouplers of photophosphorylation such as carbonylcyanide-m-chlorophenylhydrazon (CCCP) and atebrin analog abolish quenching, transient absorption change and binding of PMS. Others, such as methylamine, ammonia, gramicidin and nigericin do not. It is suggested that fluorescence quenching, transient absorption change and binding of PMS are causally related. The concept, postulated by others, that a high-energy state of the chloroplast membrane is involved in the fluorescence lowering 
  Reference    (Z. Naturforsch. 31c, 722 [1976]; received August 10 1976) 
  Published    1976 
  Keywords    Chlorophyll Fluorescence, Chloroplasts, Fluorescence Quenching, Energized Membrane 
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 TEI-XML for    default:Reihe_C/31/ZNC-1976-31c-0722.pdf 
 Identifier    ZNC-1976-31c-0722 
 Volume    31 
2Author    Michael Kom, JörnK. Üster, Herbert DreeskampRequires cookie*
 Title    Einfluß des Silberkations auf das Fluoreszenzverhalten polyzyklischer aromatischer Kohlenwasserstoffe  
 Abstract    Com bining the results o f fluorescence and triplet-triplet absorption measurements, the influence o f silver perchlorate on the excited states o f pyrene, phenanthrene, 9-cyanophenanthrene, 9,10-diphenylanthracene and 9,10-dicyanoanthracene in fluid solutions has been investigated. In corre­ spondence with a small energy gap between the lowest excited singlet state and the nearest lower triplet state an external heavy atom effect has been found to be responsible for the fluorescence quenching in the case o f pyrene, phenanthrene and 9-cyanophenanthrene. In the case o f 9,10-diphenylanthracene and 9,10-dicyanoanthracene, where this energy gap is large, an exciplex emission is observed with no significant increase o f triplet state formation. Furthermore, 9-cyanophenanthrene and 9,10-dicyanoanthracene under similar experimental conditions form ground state complexes with A gC 104 with a red-shifted fluorescence. From time-resolved fluorescence m easurements a dynamic equilibrium o f association in the excited state is deduced. 
  Reference    Z. Naturforsch. 49a, 578 (1994); eingegangen am 7. Februar 1994 
  Published    1994 
  Keywords    Fluorescence quenching, Silver ions, External heavy atom effect, Exciplex, Ground state com plexation 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0578.pdf 
 Identifier    ZNA-1994-49a-0578 
 Volume    49