No description available.

The large-scale purification of the major spinach thylakoid lipids by a combination of silica and carboxymethyl-cellulose chromatography is described. Yields of hundreds of milligrams of the lipids, representing 25-40% of the original lipid, have been obtained. In addition, routine purities in excess of 99.7% of the isolated lipids has been demonstrated. The structures of the purified lipids have been confirmed by fatty acid analysis, thin layer chromatography, and ¹³C-NMR. Some minor reassignments to previously published ¹³C-NMR for these compounds are described. In addition, the ¹H-NMR spectra for the glycolipids monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), and sulfoquinovosyldiacylglycerol (SQDG), are shown. The resonance assignments for MGDG and SQDG have been obtained by a combination of off-resonance decoupling experiments and by two-dimensional COSY ¹H-NMR experiments. Similar experiments with DGDG have failed to resolve the proton assignments due to extensive overlapping of the proton resonances. Interbilayer interactions between large unilamellar vesicles of DGDG in aqueous salt solutions have been examined by light scattering, freeze-fracture electron microscopy, and X-ray diffraction. When suspended in aqueous salt solutions, vesicles of 100 nm diameter were found to aggregate in a rapid and reversible manner to yield aggregates greater than 1000 nm in diameter. Freeze-fracture electron microscopy showed these aggregates to consist of appressed, but not fused, vesicles. Quasi-elastic light scattering and turbidity experiments showed that aggregation was not due to charged impurities of the lipid behaving in accordance with electrostatic double layer theory. Experiments testing the efficacies of various chloride salts indicated a strong correlation existed between ionic radius and ability of the salt to promote aggregation. Similar experiments examining the effect of sodium salts, glycerol, and pH on vesicle aggregation implicate an interaction between the DGDG head group and structured water as underlying the aggregation process. The effect of additions of other lipids on the extent of DGDG aggregation has been examined. Addition of 0.5 to 5.0% of either anionic lipid phosphatidylglycerol (PG) or SQDG inhibited the aggregation of DGDG vesicles, probably by the development of an electrostatic potential. Different effects of PG and SQDG on the concentration of Mg²⁺ required for aggregation indicated that PG may form a bidentate ligand with Mg²⁺ at ≥ 5 mol% PG. SQDG did not show this behavior, indicating that its negatively charged sulfonate group is unavailable for cation complex formation. Addition of MGDG to DGDG up to 50 mol% had no effect on the Mg²⁺ requirement for aggregation, but at ≥ 25 mol% triggered irreversible vesicle aggregation. This suggests that the MGDG head group is as effective at causing aggregation as the DGDG head group. Further, MGDG probably triggers vesicle fusion at ≥ 25 mol%. The results suggest that the galactolipids may contribute to the close approach of thylakoids in higher plant chloroplasts. The permeability properties of large unilamellar vesicles of DGDG to ⁸⁶Rb⁺, ³⁶Cl⁻, and ³H-glucose have been determined. In addition, the permeabilities of binary, ternary, and quaternary mixtures of thylakoid lipids to ⁸⁶Rb⁺ have also been measured. Vesicles of DGDG were found to be 60-130 fold more permeable to Rb⁺ and 46-76 fold less permeable to CI⁻ than phosphatidylcholine vesicles. Vesicles of DGDG and PC were similar in glucose permeability. Electron spin resonance measurement of DGDG bilayer fluidity indicated that fluidity differences could not account for the observed differences in ion permeability. The addition of 50 mol% of MGDG to DGDG vesicles had no effect on Rb⁺ permeability, suggesting that the HII phase preference of MGDG does not increase bilayer permeability. The addition of SQDG led to a large increase of Rb⁺ permeability. The calculated permeability coefficient to Rb⁺ for a DGDG/MDGD/SQDG/PG (1/2/0.5/0.5) mixture similar to that of thylakoid membranes was 2.0-10⁻⁹ cm-s⁻¹. This value is three orders of magnitude higher than that for phospholipid systems, and ten-fold higher than that for vesicles of pure DGDG. It is concluded that the permeability properties of thylakoid lipids are dominated by oriented surface dipoles and not by bilayer fluidity or acyl chain packing considerations. It is also proposed that the high permeability of thylakoid lipids to cations is the main cause of low observed thylakoid membrane electrical potentials, and large proton gradients across thylakoid membranes. It has been proposed previously that the high proportions of saturated phosphatidylglycerols (ie. DPPG) found in chilling-sensitive plants may promote the formation of gel phase lipid, and cause increased metabolite leakage, in the thylakoids of these species at chilling temperatures. The leakage of ⁸⁶Rb⁺ from large unilamellar vesicles of thylakoid lipids containing proportions of disaturated PG (as DPPG) mimicking those of chilling-sensitive and chilling-resistant plants has been measured. This data indicated that no increase in Rb⁺ permeation occurred between any of the tested vesicles systems between 7° and 30° C. Differential scanning calorimetry showed no heat flow indicative of gel to liquid- crystalline phase separation in any of the lipid mixtures, even with DPPG levels as high as 12 mol%. It is concluded that a direct effect of disaturated PG on chilling injury in sensitive plants by an increase of low-temperature thylakoid permeability is unlikely. / Science, Faculty of / Botany, Department of / Graduate

No description available.

Thylakoid organization and the distribution of photosystem (PS) I and II proteins in the green alga Coleochaete scutata were analyzed by electron microscopy. Thylakoids were observed to associate in varied conformations. Extended bands of thylakoids were present, as in other algae, but numerous grana, characteristic of higher plants, were also detected. Immunolabelling experiments were conducted with two heterologous antisera raised against PS proteins in the cyanobacterium Synechococcus elongatus: one antiserurn against the 60 and 62 kDa PSI reaction centre proteins, the other against the 47 kDa PSII core antenna protein. PSI was 2.6 times more concentrated in the nonappressed membranes (NAM) than in the appressed (AM), with 62% of labelling on NAM. The concentration of PSII in AM was 1.6 times that of the NAM, accounting for 75% of PSII. Thus, in C scutata, PSI and PSII are located in both appressed and nonappressed thylakoid membranes, but with a trend towards the lateral heterogeneity of PS proteins observed in higher plants. These results support the body of ultrastructural and molecular data linking charophytes with the ancestry of higher plants.

No description available.

No description available.

1. Distribution of the two photosystems (PS I and PS II) in the thylakoid membranes of the alga Euglena gracilis. The distribution of photosystem I and II (PS I and PS II) in the alga Euglena gracilis Z strain was studied by electron microscopic immunocytochemistry. In this alga, the thylakoids are not organized in gram structures, as they are in higher plants. Two different antibodies were used to identify PS I. One is directed against particles of PS I from maize and the other against the 60 and 62 kDa PS I reaction centre proteins of the cyanobacterium Synechococcus elongatus. Both antibodies demonstrated the presence of PS I in the two types of thylakoid membranes, appressed (AM) and non-appressed (NAM). Quantitative analysis showed that 60--74% of PS I is in the AM and 26--40% is in the NAM, and since about 80--90% of the membranes are AM, that PS I is more concentrated in the NAM. An antibody directed against the CP47 protein of PS II also revealed labelling in both types of thylakoid membranes (54% in AM and 46% in NAM). PS II is again more concentrated in the NAM. I demonstrated by the photo-oxidation of 3,3'-diaminobenzidine that there is PS I activity in the two types of membranes and, moreover, that there are changes in this activity during the light cycle of the cell. My results indicate that the distribution of PS I and PS II in Euglena gracilis Z strain is different from that of higher plants and is similar to that seen in green algae. The possible evolutionary significance of our observations are discussed. / 2. Localization of the protein CP47 (plastid protein) in the mitochondria of euglenoids. The localization of the CP47 protein to the mitochondria of euglenoids was studied by electron microscopic immunocytochemistry. My results demonstrate that this protein, which is coded by chloroplast DNA in all algae and plants, is present in whole or in part in the mitochondria of Euglena gracilis and related euglenoids. I used two different antibodies against the protein CP47 (anti-CP47 from Chlamydomonas reinhardtii and S. elongatus) to test wild-type, light-grown, cells of Euglena. Both antibodies selectively labelled the mitochondria. These results furthermore suggest that this labelling is particularly associated with mitochondrial cristae. Anti-CP47 from S. elongatus also labelled the mitochondria of other euglenoids, such as dark-grown cells of Euglena gracilis, the mutant Y9Z1NaL, and Astasia longa. Since the CP47 protein is present in dark-grown cells and in the mutant Y9Z1NaL, which are organisms that do not have an active psbB gene, I suggest that a gene transfer has occurred from the plastid to the mitochondria during evolution. Because our results show the presence of CP47 in the mitochondria of Astasia longa, I postulate that the transfer occurred before the branching of Astasia from Euglena.

Diss. (sammanfattning) Stockholm : Karol. inst., 2006. / Härtill 4 uppsatser.

Forest stands may act as important carbon storage places - sinks, due to carbon allocation into both the plant biomass in the process of photosynthesis and the soil. Enhancement of CO2 concentration affects a whole range of plant physiological processes and, thus, it is necessary to study its effect on photosynthetic apparatus - leaf anatomical structure and chloroplast ultrastructure. The first aim of the Thesis was to evaluate changes in chloroplast ultrastructure of common beech (Fagus sylvatica L.) under the effects of both elevated CO2 concentration and different irradiance. The second aim was to evaluate if the anatomical parameters obtained from the middle part of the leaf are representative for the whole leaf blade. The trees were grown in glass domes at the Bílý Kříž experimental site in the Beskids Mountains (Czech Republic), owned by the CzechGlobe Institute. Leaves were sampled in 2010 from juvenile trees, which were planted in 2005 being 5-year old and cultivated since then in ambient (AC; 390 micromol/mol) and elevated (EC; 700 micromol/mol) CO2 concentrations. The EC effect was recorded to be an increased proportion of starch grains in the chloroplast median section and decreased proportion of of intergranal thylakoids (IGT) while the ratio of granal to intergranal thylakoids...

Diss. (sammanfattning) Linköping : Linköpings universitet, 2007. / Härtill 4 uppsatser.