265 research outputs found
Laue Gamma-Ray Lenses for Space Astrophysics: Status and Prospects
No full textWe review feasibility studies, technological developments, and the astrophysical prospects for Laue lenses devoted
to hard X-/gamma-ray astronomy observations.</jats:p
Proton pumping bo3 oxidase from Vitreoscilla
No full textMembrane bound heme-copper oxidases reduce oxygen to water, using the released energy for vectorial proton transport across the membrane. Both reactions contribute to the generation of the proton motive force by electrogenic proton and electron transfer reactions across the membrane. These reactions are tightly coupled and precisely orchestrated to ensure energy conservation and suppression of Reactive Oxygen Species (ROS) production. Experimental discrimination between protons required for oxygen reduction and pumped protons is typically not possible. Therefore, a terminal oxidase pumping a different ion than protons would provide an elegant system to study mechanistic aspects of these intricate pumps. The group of Webster described a sodium pumping quinol oxidase in the bacterium Vitreoscilla, but no further studies have been described with this enzyme.
Our aim was thus to isolate, purify and analyse the properties of the Vitriocilla quinol oxidase to see, if it could be used a model system to elucidate the pumping mechanism using single turnover measurements with the flow-flash technique. We successfully cloned, heterologously expressed and purified the enzyme in E. coli. To our disappointment, we could neither observe sodium dependency of the enzymatic activity nor sodium pumping of the protein in inverted membrane vesicles, purified protein in detergent, or the enzyme reconstituted into proteoliposomes. Instead, we conducted several experiments that directly show proton pumping by the Vitreoscilla cytochrome bo, as compared with the related enzyme of E. coli
Rapid Electron Transfer within the III-IV Supercomplex in Corynebacterium glutamicum. And the bo3 quinol oxidase of vitreoscilla.
No full textThe gram positive soil bacterium Corynebacterium glutamicum does not harbor any water-soluble cytochrome (cyt.) c. However, complex III of the respiratory chain has a di-heme cyt. c (called here cyt. bcc). In addition, the cyt. bcc-complex co-purifies with cytochrome c oxidase (CytcO), which suggests that the two respiratory enzymes form a supercomplex. Here, we investigated the kinetics of electron transfer within the putative cyt. bcc-CytcO supercomplex and in the CytcO alone. In the reaction of the reduced detergent-purified CytcO with O2 we observed the same sequence of events and kinetics as those observed previously with other A-type CytcOs. However, even though the reaction is associated with proton uptake from solution, we did not observe any pH dependence of the kinetics. The isolated cyt. bcc-CytcO complex displayed a quinol oxidation-O2 reduction activity of ~210 s 1, which is slightly faster than the CytcO activity (~180 s 1), indicating that electron transfer via the two C-hemes of cyt. bcc is not rate limiting for the overall quinol-oxidation activity. The data also indicate that one of the C-hemes of the cyt. bcc complex occupies a position near CuA. Furthermore, we show that during O2 reduction, electrons from the C-hemes of cyt. bcc were transferred to CuA over a time scale of at least 104 s 1. After oxidation, the C-hemes were re-reduced by the B-hemes over a time scale of ~6 ms. Taken together, the data indicate rapid intracomplex electron transfer between cyt. bcc and CytcO, via the diheme cyt. c, but without any water-soluble cyt. c
SNARE-fusion mediated inserton of membrane proteins into native and artificial membranes
No full textMembrane proteins carry out functions such as nutrient uptake, ATP synthesis or transmembrane signal transduction. An increasing number of reports indicate that cellular processes are underpinned by regulated interactions between these proteins. Consequently, functional studies of these networks at a molecular level require co-reconstitution of the interacting components. Here, we report a SNARE-protein based method for incorporation of multiple membrane proteins into membranes, and for delivery of large water-soluble substrates into closed membrane vesicles. The approach is used for in vitro reconstruction of a fully functional bacterial respiratory chain from purified components. Furthermore, the method is used for functional incorporation of the entire F1F0-ATP synthase complex into native bacterial membranes from which this component had been genetically removed. The novel methodology offers a tool to investigate complex interaction networks between membrane-bound proteins at a molecular level, which is expected to generate functional insights into key cellular functions
2017 EACTS/EACTA Guidelines on patient blood management for adult cardiac surgery
No full textAuthors/Task Force Members: Christa Boer (EACTA Chairperson)(Netherlands), Michael I. Meesters (Netherlands), Milan Milojevic (Netherlands), Umberto Benedetto (UK), Daniel Bolliger (Switzerland), Christian von Heymann (Germany), Anders Jeppsson (Sweden), Andreas Koster (Germany), Ruben L. Osnabrugge (Netherlands), Marco Ranucci (Italy), Hanne Berg Ravn (Denmark), Alexander B.A. Vonk (Netherlands), Alexander Wahba (Norway), Domenico Pagano (EACTS Chairperson)(UK), Document Reviewers: Moritz W.V. Wyler von Ballmoos (USA), Mate Petricevic (Croatia), Arie Pieter Kappetein (Netherlands), Miguel Sousa-Uva (Portugal), Georg Trummer (Germany), Peter M. Rosseel (Netherlands), Michael Sander (Germany), Pascal Colson (France), Adrian Bauer (Germany)
SNARE-fusion mediated insertion of membrane proteins into native and artificial membranes
No full textMembrane proteins carry out functions such as nutrient uptake, ATP synthesis or transmembrane signal transduction. An increasing number of reports indicate that cellular processes are underpinned by regulated interactions between these proteins. Consequently, functional studies of these networks at a molecular level require co-reconstitution of the interacting components. Here, we report a SNARE protein-based method for incorporation of multiple membrane proteins into artificial membrane vesicles of well-defined composition, and for delivery of large water-soluble substrates into these vesicles. The approach is used for in vitro reconstruction of a fully functional bacterial respiratory chain from purified components. Furthermore, the method is used for functional incorporation of the entire F1F0 ATP synthase complex into native bacterial membranes from which this component had been genetically removed. The novel methodology offers a tool to investigate complex interaction networks between membrane-bound proteins at a molecular level, which is expected to generate functional insights into key cellular functions
The Relationship of Nitrate Reductase Activity to Uptake and Assimilation of Atmospheric 15NO2 -Nitrogen in Needles of Norway Spruce (Picea abies [L.] Karst.)
No full textUsing NO2, relations between nitrate reductase activity and stomatal conductance, N-uptake and N-glutamate were studied in the two youngest needles flushes of potted Norway spruce (Picea abies [L.] Karst.). There were linear correlations between the stomatal conductance and the N-uptake and between the N-uptake and nitrate reductase (E.C. 1.6.6.1/1.6.6.2) activity. The N labelling of free glutamate shows the assimilation of NO2 from the atmosphere in addition to the nitrogen from the soil. The portion of glutamate originating from NO2 was linearly related to nitrate reductase activity in spring experiments. This indicates that this enzyme activity reflected the rate of NO2-assimilation
The proton pumping bo oxidase from Vitreoscilla.
No full textThe cytochrome bo3 quinol oxidase from Vitreoscilla (vbo3) catalyses oxidation of ubiquinol and reduction of O2 to H2O. Data from earlier studies suggested that the free energy released in this reaction is used to pump sodium ions instead of protons across a membrane. Here, we have studied the functional properties of heterologously expressed vbo3 with a variety of methods. (i) Following oxygen consumption with a Clark-type electrode, we did not observe a measurable effect of Na+ on the oxidase activity of purified vbo3 solubilized in detergent or reconstituted in liposomes. (ii) Using fluorescent dyes, we find that vbo3 does not pump Na+ ions, but H+ across the membrane, and that H+-pumping is not influenced by the presence of Na+. (iii) Using an oxygen pulse method, it was found that 2 H+/e- are ejected from proteoliposomes, in agreement with the values found for the H+-pumping bo3 oxidase of Escherichia coli (ecbo3). This coincides with the interpretation that 1 H+/e- is pumped across the membrane and 1 H+/e- is released during quinol oxidation. (iv) When the electron transfer kinetics of vbo3 upon reaction with oxygen were followed in single turnover experiments, a similar sequence of reaction steps was observed as reported for the E. coli enzyme and none of these reactions was notably affected by the presence of Na+. Overall the data show that vbo3 is a proton pumping terminal oxidase, behaving similarly to the Escherichia coli bo3 quinol oxidase
Life-long growth of Quercus ilex L. at natural CO2 springs acclimates sulphur, nitrogen and carbohydrate metabolism of the progeny to elevated pCO2
No full textThe aim of the present study was to analyse whether offspring of mature Quercus ilex trees grown under life-long elevated pCO2 show alterations in the physiological response to elevated pCO2 in comparison with those originating from mature trees grown at current ambient pCO2. To investigate changes in C- (for changes in photosynthesis, biomass and lignin see Polle, McKee & Blaschke Plant, Cell and Environment 24, 1075–1083, 2001), N-, and S-metabolism soluble sugar, soluble non-proteinogenic nitrogen compounds (TSNN), nitrate reductase (NR), thiols, adenosine 5′-phosphosulphate (APS) reductase, and anions were analysed. For this purpose Q. ilex seedlings were grown from acorns of mother tree stands at a natural spring site (elevated pCO2) and a control site (ambient pCO2) of the Laiatico spring, Central Italy. Short-term elevated pCO2 exposure of the offspring of control oaks lead to higher sugar contents in stem tissues, to a reduced TSNN content in leaves, and basipetal stem tissues, to diminished thiol contents in all tissues analysed, and to reduced APS reductase activity in both, leaves and roots. Most of the components of C-, N- and S-metabolism including APS reductase activity which were reduced due to short-term elevated pCO2 exposure were recovered by life-long growth under elevated pCO2 in the offspring of spring oaks. Still TSNN contents in phloem exudates increased, nitrate contents in lateral roots and glutathione in leaves and phloem exudates remained reduced in these plants. The present results demonstrated that metabolic adaptations of Q. ilex mother trees to elevated pCO2 can be passed to the next generation. Short- and long-term effects on source-to-sink relation and physiological and genetic acclimation to elevated pCO2 are discussed
Ballon pathfinders for ultra-high energy cosmic ray detection from space : optics performance and search for air showers
No full textLes Rayons Cosmiques d'Ultra Haute Énergie (RCUHE) sont des particules chargées venant de l'espace avec des énergies >1018 eV jusqu'à une énergie mesurée de 3×1020 eV. Ils sont les messagers cosmiques les plus énergétiques, cependant leur origine et les mécanismes permettant leur accélération restent inconnus. Leur observation est difficile à cause de leur très faible flux (1 particule par stéradian par km2 par siècle) et nécessite des techniques de détection indirectes, utilisant l'atmosphère comme un calorimètre. Le projet JEM-EUSO a pour but le développement d'un télescope spatial capable d'observer les gerbes atmosphériques produites par les RCUHE par le biais de leur émission de fluorescence en UV (300 - 400 nm). Pour atteindre ces objectifs, deux projets ballons démonstrateurs ont été développés afin de tester la technologie et les méthodes requises: EUSO-Balloon et EUSO-SPB1, qui ont volé en 2014 et 2017 respectivement. Une technologie clé de ces démonstrateurs est leur système d'optique réfractive composé de deux larges lentilles de Fresnel (presque égal à 1 m2). EUSO-Balloon a volé pendant une nuit et son système optique a contribué à l'observation de traces de laser et la mesure du bruit de fond UV. Néanmoins, la performance des optiques est restée mal comprise, i.e. l'efficacité et sa fonction d'étalement du point (PSF). Ce travail explique la méthode utilisée pour caractériser la performance de l'optique et l'efficacité globale des lentilles de Fresnel. La performance mesurée peut être comprise par la combinaison d'un modèle de diffusion semi-empirique avec une simulation classique de tracé de rayon. EUSO-SPB1 a collecté des données pendant 12 nuits. On présente l'analyse des événements enregistrés suite au déclenchement de l'algorithme de "trigger". On classifie ces événements en différentes catégories et on discute leurs caractéristiques. On montre que la majorité des événements enregistrés sont des rayons cosmiques qui interagissent directement avec le détecteur ainsi que des défauts instrumentaux sur les tubes photomultiplicateurs du détecteur. Aucune gerbe atmosphérique n'a été trouvé dans cette analyse.Ultra High Energy Cosmic Rays (UHECR) are charged particles coming from outer space with energies >1018 eV up to a record measured energy of 3 × 1020 eV. They are the most energetic cosmic messengers coming to earth, however their origin and acceleration mechanisms remain a mystery. Their observation is characterized by their low flux (one particle per steradian per km2 per century) requiring indirect detection techniques using the atmosphere as a calorimeter. The JEM-EUSO framework aims at developing a space-borne telescope to observe the UHECR induced atmospheric particle cascades (air showers) through their UV fluorescence emission (300 - 400 nm). To validate JEM-EUSO's technology and methods, two balloon-borne pathfinders have been developed: EUSO-Balloon and EUSO-SPB1, they were flown in 2014 and 2017 respectively. One of the key technologies of these pathfinders is their refractive optical system consisting of two large aspherical Fresnel lenses (almost equal to 1 m2). EUSO-Balloon flew during one night and it's Fresnel optics contributed to the observation of laser tracks in the atmosphere and the measurement of the UV night-time emission. However, the performance of the optics remained misunderstood i.e. the efficiency and the point spread function. This work describes the method used to characterize the optics performance and global efficiency of the Fresnel lenses of EUSO-Balloon. The measured performance of the optics can be understood as the combination of a semi-empirical diffusion model with a classic ray tracing simulation. EUSO-SPB1 took data during 12 nights until the termination of the mission. We present an analysis of events found in triggered data while searching for air showers. We classify these events into different populations whose characteristics and origins we discuss. We show that the majority of our triggered events are direct cosmic ray interactions on the detector as well as instrumental features of the photo-multipliers. No air shower candidate was found in the analysis
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