Atomic-force microscopy imaging of plasma membranes purified from spinach leaves

Summary: Plasma membranes purified from spinach leaves by aqueous two-phase partitioning were examined by atomic-force microscopy (AFM) in phosphate buffer, and details on their structure were reported at nanometric scale. Examination of the fresh membrane preparation deposited on mica revealed a complex organization of the surface. It appeared composed of a first layer of material, about 8 nm in thickness, that practically covered all the mica surface and on which stand structures highly heterogeneous in shape and size. High-resolution imaging showed that the surface of the first layer appeared relatively smooth in some regions, whereas different characteristic features were observed in other regions. They consisted of globular-to-elliptical protruding particles of various sizes, from 4-5 nm x-y size for the smallest to 40-70 nm for the largest, and of channel-like structures 25-30 nm in diameter with a central hole. Macromolecular assemblies of protruding particles of various shapes were imaged. Addition of the proteolytic enzyme pronase led to a net roughness decrease in regions covered with particles, indicating their proteinaceous nature. The results open fascinating perspectives in the investigation of membrane surfaces in plant cells with the possibility to get structural information at the nanometric rang

Action de la lumière sur les colonies de Pseudomonas fluorescens Mig

La lumière, à dose physiologique, favorise la croissance des colonies R et S. D'autre part, elle conditionne l'expression phénotypique du caractère R

From cellular micro-compartmentation to inter-organ communications : the kinetic basis for molecular controls in photoperiodism

An autonomous self-sustained ~24 h oscillation of metabolic activity functions as a physiological clock to allow living systems seasonal adaptation of behaviour, like flowering or hibernation. Until recently circadian rhythms were considered to be a characteristic of eukaryotic cells despite a very early report by Halberg on the observation of a circadian rhythm in E. coli. With the detection of circadian oscillations of metabolic activity in Synechococcus, circadian rhythmicity has proven to exist on all levels of biological organisation from prokaryotic cells to unicellular eukaryotes to higher plants, animals and man. Circadian rhythmicity is an in viva feature of living cells and cannot be observed in vitro. Higher frequency oscillations, however, can be found in many biochemical reactions in vitro as well as in viva. This overview on rhythmic organisation of metabolism in living systems will discuss how macro-parameters like pH, ionic balances (osmos), redox state and phosphorylation potential or hydrophobicity control metabolic functions like photosynthesis, respiration, nitrogen fixation. The temporal control of metabolic pathways involves oscillatory networks in transcription, translation or posttranslational modulation of protein structure and function. Changes in macroparameter status are due to precise feedback networks in basic metabolism leading to a circadian rhythm in overall energy metabolism and thus in metabolic control of timing. Multifactorial changes in environmental conditions like light intensity and -quality, temperature, water status, ionic balances, pressure, etc. are transduced into a network of intracellular signal processing leading to a combinatorial interaction of transcription factors and outputs with cell-, tissue- and organ-specific response-patterns. Compartmentation is coupled to vectorial metabolism and electron transport and the involvement of membrane pores and ion channels. The generation of specific changes in membrane potential can be expected. The physical state of membranes is involved in the transduction of temperature signals and the control of expression of nuclear, mitochondrial and plastid genes which also can be modulated by photoreceptors like the red / far red reversible phytochromes, the blue / UV-A and the UV-B photoreceptors and the feeding of sugars. Membrane-bound processes are controlling and vice versa are controlled by voltage gated ion channels and pores, giving rise to an overall electro-chemical-hydraulic integration of organs and the whole organism on the basis of Mitchell's chemiosmotic theory of energy transduction. The electrophysiological integration offers the possibility for characterisation of cells, organs and organisms by electrophysiogrammes as a means for non-invasive continuous in vivo monitoring of physiology and behaviour

Binding of adenylate kinase to RNA.

International audienceAdenylate kinase (ATP:AMP transphosphorylase) is a key enzyme in energy metabolism. The activity of its isoforms is subjected to multiple regulations. It is shown here that a specific fraction consisting of all adenylate kinase isoforms from tobacco leaves and tissue cultures does not bind to the anionic exchange-resin Mono Q. Sample pretreatment with ribonuclease could restore full binding to Mono Q, suggesting an association of adenylate kinase with RNA similar to the enzyme of Chenopodium rubrum (J. Chromatogr. 625: 13-19). We propose here that at least in vitro adenylate kinase can behave as an RNA-binding protein and that RNA-binding of adenylate kinase isoforms may be related to regulatory mechanisms

Atomic-force microscopy imaging of plasma membranes purified from spinach leaves

Plasma membranes purified from spinach leaves by aqueous two-phase partitioning were examined by atomic-force microscopy (AFM) in phosphate buffer, and details on their structure were reported at nanometric scale. Examination of the fresh membrane preparation deposited on mica revealed a complex organization of the surface. It appeared composed of a first layer of material, about 8 nm in thickness, that practically covered all the mica surface and on which stand structures highly heterogeneous in shape and size. High-resolution imaging showed that the surface of the first layer appeared relatively smooth in some regions, whereas different characteristic features were observed in other regions. They consisted of globular-to-elliptical protruding particles of various sizes, from 4-5 nm x-y size for the smallest to 40-70 nm for the largest, and of channel-like structures 25-30 nm in diameter with a central hole. Macromolecular assemblies of protruding particles of various shapes were imaged. Addition of the proteolytic enzyme pronase led to a net roughness decrease in regions covered with particles, indicating their proteinaceous nature. The results open fascinating perspectives in the investigation of membrane surfaces in plant cells with the possibility to get structural information at the nanometric range

Investitionen zur Verminderung von Umeltbelastungen. Gemeinschaftsklaerwerk Bitterfeld-Wolfen Abschlussbericht

Errichtung eines Gemeinschaftsklaerwerks (422.000 EW) fuer die Region Bitterfeld-Wolfen zur gemeinsamen Reinigung des Abwassers der Chemieindustrie und der Kommunen, organisiert als GmbH mit kommunaler Mehrheit. Zuleitung des Abwassers ueber 18 Pumpwerke mit 42 km Druck-/Freispiegelleitungen. Ausfuehrung der Abwasserreinigungsanlage in Hochbauweise mit getrennter Vorbehandlung und gemeinsamer biologischer Reinigung in 4 BIOHOCH "t"r"a"d"e"m"a"r"k -Reaktoren (fuer Industrieabw. 2-stufig). Klaerschlammbehandlung im Wirbelschichtofen mit nachgeschalteter Rauchgasreinigung. Investitionsvolumen der gesamten Anlage 380 Mio. DM. (orig.)SIGLEAvailable from TIB Hannover: RO 2148(7031) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Umwelt, Naturschutz und Reaktorsicherheit, Bonn (Germany); Umweltbundesamt, Berlin (Germany); Ministerium fuer Raumordnung, Landwirtschaft und Umwelt des Landes Sachsen-Anhalt, Magdeburg (Germany)DEGerman