Build-up of the energized state of thylakoid membranes and the synthesis of ATP are warranted by organizing their bulk lipids into a bilayer. However, the major lipid species of these membranes, monogalactosyldiacylglycerol, is a non-bilayer lipid. It has also been documented that fully functional thylakoid membranes, in addition to the bilayer, contain an inverted hexagonal (HII) phase and two isotropic phases. To shed light on the origin of these non-lamellar phases, we performed 31P-NMR spectroscopy experiments on sub-chloroplast particles of spinach: stacked, granum and unstacked, stroma thylakoid membranes. These membranes exhibited similar lipid polymorphism as the whole thylakoids. Saturation transfer experiments, applying saturating pulses at characteristic frequencies at 5 °C, provided evidence for distinct lipid phases-with component spectra very similar to those derived from mathematical deconvolution of the 31P-NMR spectra. Wheat-germ lipase treatment of samples selectively eliminated the phases exhibiting sharp isotropic peaks, suggesting easier accessibility of these lipids compared to the bilayer and the HII phases. Gradually increasing lipid exchanges were observed between the bilayer and the two isotropic phases upon gradually elevating the temperature from 5 to 35 °C, suggesting close connections between these lipid phases. Data concerning the identity and structural and functional roles of different lipid phases will be presented in the accompanying paper.

• Klíčová slova
• 31P-NMR, DEM—dynamic exchange model, HII phase, bilayer membrane, grana, isotropic phase, non-bilayer lipids, non-lamellar lipid phases, structural flexibility, thylakoid membranes,
• MeSH
• chloroplasty chemie   MeSH
• galaktolipidy chemie   MeSH
• magnetická rezonanční spektroskopie metody   MeSH
• membránové lipidy chemie   MeSH
• teplota MeSH
• tylakoidy chemie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• galaktolipidy MeSH
• membránové lipidy MeSH
• monogalactosyldiacylglycerol MeSH Prohlížeč

The composition of plant membrane lipids was investigated by reversed-phase high performance liquid chromatography mass spectrometry with accurate mass measurement. The data dependent methods for the analysis of monogalactosyldiacylglycerols (MGDGs) and digalactosyldiacylglycerols (DGDGs) have been developed. The optimised chromatographic systems were based on a 2.0 mm i.d. Nucleosil C18 column with methanol/water (MGDGs) or acetonitrile/methanol/water (DGDGs) gradients. The galactolipids were ionised by electrospray operated in the positive ion mode and identified based on their MS/MS spectra. High resolution spectra with accurate masses were found to be essential for correct interpretation of the MS data. The elution order of non-oxidised MGDGs and DGDGs followed the equivalent carbon numbers. The methods were applied for detailed characterisation of the MGDGs and DGDGs in the leaves of Arabidopsis thaliana and Melissa officinalis.

• MeSH
• Arabidopsis chemie   MeSH
• chromatografie s reverzní fází MeSH
• galaktolipidy chemie   MeSH
• hmotnostní spektrometrie s elektrosprejovou ionizací MeSH
• meduňka chemie   MeSH
• oxidace-redukce MeSH
• vysokoúčinná kapalinová chromatografie MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• galaktolipidy MeSH
• monogalactosyldiacylglycerol MeSH Prohlížeč

Aggregation of bacteriochlorophyll (BChl) c from chlorosomes, the main light-harvesting complex of green bacteria, has been studied in aqueous buffer. Unlike other chlorophyll-like molecules, BChl c is rather soluble in aqueous buffer, forming dimers. When BChl c is mixed with carotenoids (Car), the BChl c Qy transition is further redshifted, in respect to that of monomers and dimers. The results suggest that Car are incorporated in the aggregates and induce further aggregation of BChl c. The redshift of the BChl c Qy band is proportional to the Car concentration. In contrast, the mixture of bacteriochlorophyllide (BChlide) c, which lacks the nonpolar esterifying alcohol, does not form aggregates with Car in aqueous buffer or nonpolar solvents. Instead, the position of the BChlide c Qy transition remains unshifted in respect to that of the monomeric molecule, and Car precipitates with the course of time in aqueous buffer. Similar effects on both BChl c and BChlide c are also observed when monogalactosyl diglyceride (MGDG), which forms the monolayer envelope of chlorosomes, is used instead of (or together with) Car. The results show that the hydrophobic interactions of the BChl c esterifying alcohols with themselves and the nonpolar carbon skeleton of Car, or the fatty acid tails of MGDG, are essential driving forces for BChl aggregation in chlorosomes.

• MeSH
• bakteriální proteiny chemie   MeSH
• bakteriochlorofyly chemie   MeSH
• Chlorobium chemie   MeSH
• galaktolipidy chemie   farmakologie   MeSH
• karotenoidy chemie   farmakologie   MeSH
• pufry MeSH
• rozpustnost MeSH
• spektrální analýza MeSH
• vazba proteinů účinky léků   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• bacteriochlorophyll c MeSH Prohlížeč
• bakteriální proteiny MeSH
• bakteriochlorofyly MeSH
• galaktolipidy MeSH
• karotenoidy MeSH
• pufry MeSH