Browsing by Author "Strasser, Reto J."

Now showing 1 - 6 of 6

Open Access
Altered lipid matrix changes energy distribution in thylakoids
(1987) Graf, Josef A.; Strasser, Reto J.; Kull, Ulrich
Photosynthetic membranes differ from other cellular rnembranes in that they have a thylakoid specific lipid composition and a high degree of polyunsaturated fatty acids. The typical acyl lipid complement of thylakoids seems to have two functions: the organization of the membrane matrix in which the pigment protein complexes are embedded and the indirect structure-function relationships between lipid matrix and pigment protein complexes which influence energy distribution behaviour. The role of high amounts of polyunsaturated fatty acids and indirect structure-function rclationships can be studied by inhibiting fatty acid desaturation sequence with pyridazinone herbicides.
Open Access
Changes of the membrane matrix rearrange pigment complexes : abstract only
(1984) Graf, Josef A.; Strasser, Reto J.; Kull, Ulrich
-
Open Access
Comparative measurements of membrane potentials with microelectrodes and voltage-sensitive dyes
(1984) Bräuner, Thomas; Hülser, Dieter F.; Strasser, Reto J.
The usefulness of a new voltage-sensitive fluorescent dye, the membrane permeant negatively charged oxonol dye diBA-C4-(3)−, was evaluated by measuring the membrane potentials of BICR/M1R-k and L cells with glass microelectrodes and simultaneously recording the fluorescence of the stained cells. The membrane potential of BICR/M1R-k cells was varied between −25 mV and −90 mV by changing the bicarbonate concentration in the medium or by voltage clamping. To avoid any interference by the inserted electrodes with the fluorescence measurement of the cytoplasm, the cells were fused by polyethyleneglycol to form giant cells (homokaryons). These homokaryons also allowed penetration by two glass microelectrodes without causing a serious leakage of the plasma membrane. The slow responding dye diBA-C4-(3)− had a fluorescence response of about 1% per mV. Mathematical analysis of the fluorescence changes after voltage clamping revealed a first-order reaction with a rate constant between 0.1 min−1 and 0.8 min−1, depending on the cell size which was determined by the number of nuclei per homokaryon. A model for the mechanism of the fluorescence changes is proposed.
Open Access
Pyridazinone/cytokinin antagonism regulates energy distribution : [abstract]
(1986) Graf, Josef A.; Strasser, Reto J.; Kull, Ulrich
-
Open Access
State-1 state-2 transition influenced by herbicides which modify fatty acid composition in leaves
(1984) Graf, Josef A.; Strasser, Reto J.; Kull, Ulrich
Interactions of herbicides with photosynthetic membranes are still not solved in many respects. Three different modes of action have been reported for pyridazinone herbicides : inhibition of (1) photosynthetic electron transport (2) carotenoid biosynthesis and (3) fatty acid desaturation in the galactolipid fraction of chloroplasts. The pyridazinone BASF 13-338 (=SAN 9785) used in our investigations has no effect on pigmentsynthesis and photosynthetic activity but affects fatty acid desaturation in leaves. Cerulenin an antibiotic from the fungus Cephalosporium caerulens inhibits fatty acid synthesis generally. Both herbicides act indirectly on photosynthesis because they alter the mobility of photosynthetic units in the membrane.
Open Access
Structure-function-relationship in thylakoids influenced by the pyridazinone BAS 13-338 (SAN 9785)
(1987) Graf, Josef A.; Strasser, Reto J.; Kull, Ulrich
The pyridazinone SAS 13-338 (SAN 9785) inhibits the desaturation sequence leading to polyunsaturated fatty acids, mainly of glycolipids. Parallel to the inhibition of fatty acid desaturation in the presence of the pyridazinone. changes in energy-distribution parameters have been observed. These data indicate that the amount of polyunsaturated fatty acids in glycolipids is strongly correlated with excitation, trapping, grouping and dissipation, but not with spillover. Functional changes in energy distribution induced by SAS 13-338 are interpreted as a consequence of structural changes in the lipid matrix, which may imply a structure-function relationship between pigment protein complexes and the surrounding lipid environment in thylakoids.