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1984 (1)
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1975 (1)
1Author    G. Schäfer, A. Trebst, K. H. BüchelRequires cookie*
 Title    2-Anilino-1.3.4-thiadiazole, Hemmstoffe der oxidativen und photosynthetischen Phosphorylierung 2-Anilino-l,3,4-Thiadiazoles, Inhibitors of Oxidative and Photosynthetic Phosphorylation  
 Abstract    2-anilino-l,3,4-thiadiazoles carrying various substituents in the 5-position as well as in the benzene-ring were synthesized. The compounds were tested with rat-liver-mitochondria and with spinach-chloroplasts and revealed to be potent uncouplers of both, oxidative and photosynthetic phosphorylation, with p l50-values rangeing from 6.79 to 4.05. At higher concentration all compounds are inhibitors of the Hill-reaction. In mitochondria a fair correlation exists between pKa of the acidic NH-group and the un­ coupling activity; a maximum is obtained around pKa= 6 .8 , whereas in chloroplasts activity is shifted to more acid pKa-values. The compounds meet the requirements for uncouplers according to the chemi-osmotic theory, being lipophilic weak acids. N-methylation causes total loss of activity in mitochondrial oxidative phosphorylation. The inhibitory action on photosynthetic electron transport is located within photosystem II. This latter activity is almost independent of substituent effects in contrast to uncoupling of either respiratory-or photo-phosphorylation. 
  Reference    (Z. Naturforsch. 30c, 183 [1975]; eingegangen am 19. Dezember 1974) 
  Published    1975 
  Keywords    Oxidative Phosphorylation, Photophosphorylation, Uncouplers, Structure-function Correlation 
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 TEI-XML for    default:Reihe_C/30/ZNC-1975-30c-0183.pdf 
 Identifier    ZNC-1975-30c-0183 
 Volume    30 
2Author    G. Erard Van Den Berg, M. Arjo, B. Randse, Jaco, T. Ip, D. U. Ph, A.R B VRequires cookie*
 Title    Effects of Substituted 2-Phenylamino-l,4,5,6-tetrahydropyrimidines on ATP Formation in Isolated Spinach Chloroplasts  
 Abstract    The effects o f a series o f 2-arylam ino-l,4,5,6-tetrahydropyrim idines on photosynthesis in spin­ ach chloroplast were studied. The com pounds proved to be uncouplers o f photophosphorylation, while inhibition o f electron transport occurred at higher concentrations. These effects were rather irreversible and the activity increased with lipophilicity. Inhibition o f electron transport could not be reversed by trypsin treatmeni. Loss o f membrane integrity m ight be the underlying m echanism o f these effects. 
  Reference    Z. Naturforsch. 37c, 651—657 (1982); received April 2 1982 
  Published    1982 
  Keywords    Arylaminopyrimidines, Photophosphorylation, Electron Transport, Chloroplasts, uncouplers 
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 TEI-XML for    default:Reihe_C/37/ZNC-1982-37c-0651.pdf 
 Identifier    ZNC-1982-37c-0651 
 Volume    37 
3Author    ElenaA. Kotova, MarinaD. Il 'inaRequires cookie*
 Title    Effect of Electron Transfer Inhibitors and Uncoupling Agents on the Chlorophyll Fluorescence Lifetime during Slow Fluorescence D ecline in Bean Leaves and Intact Chloroplasts  
 Abstract    Fluorescence m easurem ents were performed with bean leaves and intact chloroplasts, which are characterized by a slow fluorescence decline. The fluorescence lifetime (r) ana the fluores­ cence relative quantum yield (q>) o f intact chloroplasts, measured with the phase fluorometer, showed nearly proportional light-induced decrease with a halftime o f ~ 3 0 s, which was removed by 3-(3.4-dichlorophe n y l)-1.1 -dimethylurea (DC M U), by 4.5,6,7-tetrachloro-2'-trifluoromethyl-benzimidazole (TTFB). by carbonyl cyanide /?-trifluoromethoxyphenylhydrazone (FCCP) at a low concentration and by gramicidin D. Simultaneously the slow light-induced increase in absorbance at 518 nm (A A 518), reflecting thylakoid membrane energization, was elim inated. The data on r o f intact chloroplasts are original, the other results agree with literature data. In leaves, the slow light-induced fluorescence decline, with r dropping from ~ 2 to ~ 0.6 ns, was abolished by FCCP at a concentration o f 5 ^m. However, while r was stabilized at a level close to the initial (maximum) one or som ewhat higher, q> became close to the minimum value. Besides, the amplitude o f A A 518 was lowered about three times. These effects seemed to be due to multiple action o f FCCP as a protonophoric uncoupler and an electron transfer inhibitor. In the presence o f another uncoupling agent, TTFB, which, besides, is a diuron-like inhibitor o f the electron transfer in chloroplasts, we observed the light-dependent, but hardly linked to changes in membrane potential, great increase in r o f a leaf from ~ 1.9 to ~ 4 .3 ns, with cp decreasing slightly. Addition o f DC M U together with FCCP to the incubation medium or infiltration o f a leaf with DCM U alone stimulated the rise in r only to ~ 3 ns. The increase in r o f a leaf observed in the presence o f FCCP and DCM U, and especially with TTFB, may be associated with protein conformation changes which (i) alter the lifetime o f nanosecond recombination lum inescence o f the photosystem II a n d /o r (ii) disturb excitation energy transfer from the light-harvesting chlorophyll a /b com plex to other pigment-protein complexes. 
  Reference    Z. Naturforsch. 39c, 93—101 (1984); received October 5 1983 
  Published    1984 
  Keywords    Photosynthesis, C hlorophyll Fluorescence Lifetime, Electron Transfer Inhibitors, Uncouplers, Bean Leaves, Intact Chloroplast 
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 TEI-XML for    default:Reihe_C/39/ZNC-1984-39c-0093.pdf 
 Identifier    ZNC-1984-39c-0093 
 Volume    39