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A Trebst

Publications and source records attributed to A Trebst.

42 records · Page 3Linked to original sources
PubMedDate not supplied

Shuttles of artificial electron donors for photosystem I across the thylakoid membrane.

NADP+ reduction in isolated chloroplasts of spinach by photosystem I at the expense of various artificial donor systems is not inhibited by the plastoquinome antagonist dibromothymoquinone. The coupled ATP formation in such photoreductions is attributed to an artificial energy conserving site, i. e. a proton liberation during oxidation of the donor at the inner surface of the thylakoid membrane. Some donor systems for photosystem I are stimulated by uncouplers whereas others are not. The stimulation shows no correlation to the efficiency of the coupled photophosphorylation. Instead a correlation of the stimulation by uncouplers to the presence of an acidic OH-group in the donor molecule is seen. The uncoupler effect is therefore not explained by a release of electron transport control by the high energy state but rather by a pH-dependent distribution of the donor compound across the membrane. This is supported by the properties of donor systems in sonicated chloroplast particles with external oxidation sites of photosystem I.

Adenosine Triphosphate↗
PubMedDate not supplied

[2-anilino-1,3,4-thiadiazoles, inhibitors of oxidative and photosynthetic phosphorylation (author's transl)].

2-anilino-1,3,4-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 revelaed to be potent uncouplers of both, oxidative and photosynthetic phosphorylation, with pI50-values rangeing from 6.79 to 4.05. At higher concentrations all compounds are inhibitors of the Hill-reaction. In mitochondria a fair correlation exists between pKa of the acidic NH-group and the uncoupling activity; a maximum is obtained around pKa equals 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 ingibitory 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.

Animals↗
PubMedDate not supplied

[Mode of action and structure-acitivity-relationships of the aminotriazinone herbicide Metribuzin. Inhibition of photosynthetic electron transport in chloroplasts by Metribuzin (author's transl)].

The influence of the aminotriazinone herbicide Metribuzin on photosynthetic reactions of isolated chloroplasts is investigated. Metribuzin inhibits all Hill-reactions when water is the electron donor, but not photoreductions by photosystem I at the expense of an artifical electron donor. The PI59-value is 6.7. Cyclic photophosphorylation is not affected by Metribuzin. Measurements of the prompt and delayed fluorescence of the photosynthetically active chlorophyll support the notion, that Metribuzin inhibits photosynthetic electron flow between the primary and seondary electron acceptor of photosystem II (Q and plastoquinone). The relationship of inhibitory potency to chemical structure is investigated by comparing a number of related aminotriazinones. The effect of various substituents is discussed.

Chlorella↗