Chemie, Biochemie und ökologische Bedeutung der verletzungsaktivierten Transformation von Sekundärmetaboliten in der Grünalge Caulerpa taxifolia

Die einzellige tropische Makroalge Caulerpa taxifolia verfügt über die Fähigkeit, verletzte Zellteile durch die schnelle Bildung eines gelartigen Wundverschlusses zu verschließen, wodurch das Überleben und die ungeschlechtliche Vermehrung der Alge ermöglicht wird. Bei der Wundreaktion wird das gespeicherte Sesquiterpen Caulerpenin enzymatisch zu dem reaktiven ungesättigten 1,4-Dialehyd Oxytoxin 2 deacetyliert. Modellreaktionen mit Aminosäuren zeigen, dass Oxytoxin 2 durch die Reaktion mit freien Thiol- und Aminogruppen als Proteinquervernetzer wirkt. Durch die Quervernetzung von Proteinen entsteht ein Biopolymer, welches der Alge als Wundverschluss dient. Dadurch ist die verwundete Alge an einigen Aminosäuren abgereichert, was sie für bestimmt Fraßfeinde unattraktiv macht

Chemie, Biochemie und ökologische Bedeutung der verletzungsaktivierten Transformation von Sekundärmetaboliten in der Grünalge Caulerpa taxifolia

Die einzellige tropische Makroalge Caulerpa taxifolia verfügt über die Fähigkeit, verletzte Zellteile durch die schnelle Bildung eines gelartigen Wundverschlusses zu verschließen, wodurch das Überleben und die ungeschlechtliche Vermehrung der Alge ermöglicht wird. Bei der Wundreaktion wird das gespeicherte Sesquiterpen Caulerpenin enzymatisch zu dem reaktiven ungesättigten 1,4-Dialehyd Oxytoxin 2 deacetyliert. Modellreaktionen mit Aminosäuren zeigen, dass Oxytoxin 2 durch die Reaktion mit freien Thiol- und Aminogruppen als Proteinquervernetzer wirkt. Durch die Quervernetzung von Proteinen entsteht ein Biopolymer, welches der Alge als Wundverschluss dient. Dadurch ist die verwundete Alge an einigen Aminosäuren abgereichert, was sie für bestimmt Fraßfeinde unattraktiv macht

Short synthesis of labeled and unlabeled 6Z,9Z,12Z,15-hexadecatetraenoic acid as metabolic probes for biosynthetic studies on diatoms

Max-Planck-Institute for Chemical Ecology, Hans-Knoll-Str. 8, D-07745 Jena, Germany. [email protected] We describe a short synthesis of the unusual polyunsaturated 6Z,9Z,12Z,15-hexadecatetraenoic acid found in marine and fresh water diatoms. Using a one pot reductive bis-Wittig-olefination, the homoconjugated tetraene backbone of the fatty acid can be generated from easy available precursors. Reductive olefination allows the non-statistical dissymmetrisation of a symmetrical bis-Wittig salt as key synthon. This short sequence was also applied to the generation of the corresponding 9,10-[(2)H(2)] labeled fatty acid. If administered to cell fragments of Thalassiosira rotula 9,10-[(2)H(2)]-6Z,9Z,12Z,15-hexadecatetraenoic acid is transformed oxidatively to the aldehyde 1,2-[(2)H(2)]-2E,4E/Z,7-octatrienal which is involved in the chemical defense of this alga. Using the synthetic standard it could be shown that the C16:4 omega1 fatty acid is released upon wounding of T. rotula cells. The synthesis with the labeled bis-Wittig salt is of general use and can also be applied for the fast generation of other internally labeled functionalized and non-functionalized polyunsaturated fatty acids. To our knowledge this represents the first synthesis of 6Z,9Z,12Z,15-hexadecatetraenoic acid

Reduction of herbivory through wound-activated protein cross-linking by the invasive macroalga Caulerpa taxifolia

aldehydes chemical defense food quality protein cross-linking protein modification

Cytotoxicity of diatom-derived oxylipins in organisms belonging to different phyla

Max-Planck Institute, Hans-Knoll-Str. 8, D-07745 Jena, Germany. The cytotoxicity of several saturated and unsaturated marine diatom-derived aldehydes and an oxo-acid have been screened in vitro and in vivo against different organisms, such as bacteria, algae, fungi, echinoderms, molluscs and crustaceans. Conjugated unsaturated aldehydes like 2E,4E-decadienal, 2E,4E-octadienal, 5E,7E-9-oxo-nonadienoic acid and 2E-decenal were active against bacteria and fungi and showed weak algicidal activity. By contrast, the saturated aldehyde decanal and the non-conjugated aldehyde 4Z-decenal had either low or no significant biological activity. In assays with oyster haemocytes, 2E,4E-decadienal exhibited a dose-dependent inhibition of cytoskeleton organisation, rate of phagocytosis and oxidative burst and a dose-dependent promotion of apoptosis. A maternal diatom diet that was rich in unsaturated aldehydes induced arrest of cell division and apoptotic cell degradation in copepod embryos and larvae, respectively. This wide spectrum of physiological pathologies reflects the potent cell toxicity of diatom-derived oxylipins, in relation to their non-specific chemical reactivity towards nucleophilic biomolecules. The cytotoxic activity is conserved across six phyla, from bacteria to crustaceans. Deregulation of cell homeostasis is supposed to induce the elimination of damaged cells through apoptosis. However, efficient protection mechanisms possibly exist in unicellular organisms. Experiments with a genetically modified yeast species exhibiting elevated membrane and/or cell wall permeability suggest that this protection can be related to the inability of the oxylipin compounds to enter the cell

Extreme ultraviolet fluorescence spectroscopy of pure and core-shell rare gas clusters at FLASH

Rare gas clusters exposed to strong laser fields at short wavelength have attracted considerable interest in the last decade. The most common way to study the interaction is by time-of-flight spectroscopy of the resulting charged particles. However, recent imaging experiments give evidence that the measured mass spectra do not reflect the charge states that are initially formed. We present experiments on pure and core-shell Xe and Ar clusters to analyze the initially produced charge states by their extreme ultraviolet fluorescence. The clusters were excited by strong free-electron laser pulses from FLASH at 13 nm. Characteristic fluorescence of multiply charged species reveals detailed information on energy deposition and redistribution as a function of cluster size and FEL intensity. Of particular interest are charge transfer processes as function of the cluster composition in core-shell systems