189 research outputs found
Mesure de la fréquence d'oscillation des mésons B utilisant les leptons, les kaons, et la charge de jet avec le détecteur DELPHI à LEP
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Lyotropic liquid-crystal side-chain polymers and elastomers
No full textDas Phasenverhalten lyotroper Flüssigkristalle im wässrigen Medium wurde unter-sucht. Das Hauptaugenmerk lag dabei auf Seitenkettenpolymeren und den korres-pondierenden Elastomeren. Anhand von zwei verschiedenen Syntheseansätzen wurde der Einfluss der HLB und der Geometrie auf das lyotrope Phasenverhalten untersucht. Durch gezielte Variation der geometrisch bedingten Packungseffekte sollte der Aufbau verschiedener Flüssigkristallphasen erreicht werden. Weitergehend wurde das Orientierungsverhalten von Elastomeren untersucht. Zur Herstellung amphiphiler Polymere wurden lipophile Bisepoxide und ein hydrophiles primäres Amin synthetisiert und polymerisiert Durch Variation des Substitutionsmusters am aromatischen Ring des hydrophoben Monomers konnte die notwendige parallele Anordnung der Moleküle und die Aggregation zu einer Schichtstruktur unterstützt oder benachteiligt werden. In einem anderen Syntheseansatz wurden Monomere aus vinylterminierten Benzoe-säurephenylester und Ethylenoxidketten unterschiedlicher Länge und Geometrie synthetisiert. Es wurden verschiedene Seitenkettenpolymere des Kettenendtyps her-gestellt und charakterisiert. Die starre, stäbchenförmige Struktur der hydrophoben Komponente induziert bevorzugt eine lamellare Lα Phase. Das Phasenverhalten ist in Übereinstimmung mit dem Konzept von Isrealachvili, bei dem für das Ausbilden einer bestimmten Phasenstruktur ausschließlich Packungseffekte verantwortlich sind. Durch ihre gezielte Variation konnten somit Übergänge zwischen verschiedenen lyotropen Phasen erreicht werden. Aus den Polymeren wurden die korrespondierenden Elastomere als Polydomäne synthetisiert. Die lyotrop flüssigkristallinen Gummis zeigen das gleiche Phasen-verhalten wie die zugehörigen Polymere. Eine lyotrop flüssigkristalline Monodomäne konnte durch eine zweistufe Vernetzung (biaxiales Entquellen) erhalten werden. Die einheitliche Orientierung des Hydrogels wurde durch die verankerte oblate Vorzugs-konformation induziert.The phase behavior of lyotropic liquid crystal in aqueous systems has been investigated. Main focus was on amphiphilic side-chain polymers and corresponding elastomers. The influence of the HLB (hydrophilic-lipophilic-balance) on the lyotropic phase behavior was investigated by use of two different synthetic approaches. The formation of different liquid crystal phases shall be achieved through variation of geometric packaging effects. The influence of mechanical fields on the orientational behavior of elastomers is investigated.
Amphiphilic polymers have been synthesized through polymerization of lipophilic Bisepoxides and a hydrophilic Amine. Through variation of the substitution pattern of the aromatic core the parallel order and the aggregation to a layered structure was achieved. In a second synthetic approach vinyl terminated hydrophobic benzoic acid phenylesters and hydrophilic ethylenoxid chains of different length and geometry have been synthesized. Different side-chain polymers with linear or swallowtailed geometry f the hydrophilic moieties have been synthesized and characterized. Due to the rigid and rod like geometry the formation of a lamellar phase is favored. The observed phase behavior is in compliance with the concept of Isrealachvili, which concludes the strong influence of packaging restrictions on the phase structure. Through variation of geometry different lytropic phases have been achieved.
The corresponding polydomain elastomers have been synthesized. The lyotropic liquid crystalline rubbers show temperature and concentration depending phase behavior similar to the linear polymers. By a two-step synthesis and biaxial deswelling a lyotropic monodomain Elastomer has been synthesized. The overall uniform orientation of the hydrogel was achieved by the synthetically fixed oblate chain conformation.
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Structural and biochemical characterization of an antiphage defence system in Bacillus subtilis
No full textAt least two mobile genetic elements can be observed in certain strains of Bacillus subtilis – the integrative and conjugative element ICEBs1 [1,2], and the temperate phage SPß [3]. The spbK gene in ICEBs1 inhibits the production of active SPß. Its gene product, BsSPBK1, contains a TIR domain that is necessary for function [4]. TIR domains are known to show NADase activity [5], suggesting that BsSPBK1 could also be an NADase effector and elicits abortive infection that leads to cell death. The abortive infection depends on the SPß gene yonE, where co-expression of spbK and yonE inhibits the growth of host cells [4]. The exact function of yonE is not known yet. Its encoded protein, YonE, shares similarity with viral capsid portal proteins [6]. The mechanism of how YonE and BsSPBK1 trigger an antiphage response is poorly understood. In this study, we have confirmed that BsSPBK1 has NADase activity and is modulated by YonE. A ~3Å cryoEM reconstruction of YonE suggests that the protein assembles into a dodecamer as expected for portal proteins. The EM density map fits well with the YonE dodecameric model predicted by AlphaFold2 [7]. We have also obtained a ~3.3Å cryoEM reconstruction of BsSPBK1 filaments and model fitting suggests that the TIR domains self-assemble to form filaments. We hypothesize that this self-assembly of TIR domains in BsSPBK1 forms active sites capable of cleaving NAD+ [8]. Negative stain electron microscopy results have indicated that filament formation is enhanced in the presence of YonE, resulting in a higher density of longer filaments. A cryoEM structure of the YonE- BsSPBK1 complex will provide key insights into how YonE interacts with BsSPBK1 to modulate its NADase activity. To this end, we have produced and screened a mutant of BsSPBK1 that forms shorter filaments with less bundling, and are now in the process of collecting cryoEM data in the presence of YonE.No Full Tex
Sustained-release microparticle dry powders of chloramphenicol palmitate or thiamphenicol palmitate prodrugs for lung delivery as aerosols
No full textInternational audienceThe purpose of this study was to design inhalable sustained-release nanoparticle-in-microparticles, i.e. nano-embedded microparticles, for the lung delivery of chloramphenicol or thiamphenicol as aerosols. The palmitate ester prodrugs of the two antibiotics were used to prepare PLGA-based nanoparticles or to form pure prodrug nanoparticles. Prodrug-loaded PLGA nanoparticles or pure prodrug nanoparticles were prepared using the emulsion-solvent evaporation method. Dry microparticle powders for inhalation were then produced by spray-drying the nanoparticle suspensions supplemented with lactose as a bulking agent and L-leucine as a dispersing enhancer. Examined under the scanning electron microscopy, the obtained microparticles appeared to be spherical and shriveled, with no crystal-like structures. Drug loading was satisfactory (14 to 34% (m/m)) and the aerodynamic properties determined with a Next Generation Impactor were appropriate for lung delivery, with mass median aerodynamic diameters close to 3 μm. The in vitro release profiles showed that sustained released was achieved with these formulations, with an almost complete release over 14 days
Engineering recombinant virus-like nanoparticles from plants for cellular delivery
No full textUnderstanding capsid assembly following recombinant expression of viral structural proteins is critical to the design and modification of virus-like nanoparticles for biomedical and nanotechnology applications. Here, we use plant-based transient expression of the Bluetongue virus (BTV) structural proteins, VP3 and VP7, to obtain high yields of empty and green fluorescent protein (GFP)-encapsidating core-like particles (CLPs) from leaves. Single-particle cryo-electron microscopy of both types of particles revealed considerable differences in CLP structure compared to the crystal structure of infection-derived CLPs; in contrast, the two recombinant CLPs have an identical external structure. Using this insight, we exploited the unencumbered pore at the 5-fold axis of symmetry and the absence of encapsidated RNA to label the interior of empty CLPs with a fluorescent bioconjugate. CLPs containing 120 GFP molecules and those containing approximately 150 dye molecules were both shown to bind human integrin via a naturally occurring Arg-Gly-Asp motif found on an exposed loop of the VP7 trimeric spike. Furthermore, fluorescently labeled CLPs were shown to interact with a cell line overexpressing the surface receptor. Thus, BTV CLPs present themselves as a useful tool in targeted cargo delivery. These results highlight the importance of detailed structural analysis of VNPs in validating their molecular organization and the value of such analyses in aiding their design and further modification
Determination of ǀVcb☐from the semileptonic decay B0 → D*-l+ν
No full textSemileptonic decays B→ D*-l+νX were selected from a sample of 3.1 million hadronic Z decays collected by the DELPHI detector at LEP. A topological search for semileptonic B decays to resonant and non-resonant D*-π+ states was performed and the ratio of the branching fractions: Br(B → D*-l+νX)/Br(B → D*-+νX) + Br(B0 → + D*-l+ν) = 0.19 ± 0.10(stat) ± 0.06(syst) was determined. Taking into account this contribution, the differential decay width of B0 → D*-l+ν was measured as a function of the momentum transfer from the B to the D*- in two separate analyses, using exclusive and inclusive methods of D*- reconstruction. The distributions were fitted over the full momentum transfer range to extract the product of {pipe}Vcb{pipe} times the normalization of the decay form factor F(q2max): F(q2max){pipe}Vcb{pipe} = (35.4 ± 1.9(stat) ± 2.4(syst)) · 10-3. The value of {pipe}Vcb{pipe} was computed using theoretical calculations of F(q2max), giving: {pipe}Vcb{pipe} = (38.9 ± 2.0(stat) ± 2.6(syst) ± 1.7(theory)) · 10-3. The total branching fraction Br(B0 → D*-l+ν) was determined to be: Br(130, D*-l+v) = (5.52 ± 0.17(stat) ± 0.68(syst))%. © Springer-Verlag 1996
A MEASUREMENT OF B+ AND B-0 LIFETIMES USING (D)OVER-BAR-L(+) EVENTS
No full textA measurement of B meson lifetimes is presented using data collected from 1991 to 1993 by the DELPHI detector at the LEP collider, Samples of events with a D meson and a lepton in the same jet are selected where () over bar D**l(+)v, the following B meson lifetimes and lifetime ratio are measured: tau(B+) = 1.61(-0.16)(+0.16) (stat.) +/- 0.12 (syst.) ps tau(B-0) = 1.61(-0.13)(+0.14) (stat.) +/- 0.08 (syst.) ps tau (B+)/tau(B-0) = 1.00(-0.15)(+0.17) (stat.) +/- 0.10 (syst.) and an average lifetime of B+ and B-0 mesons is obtained: tau(B) = 1.61(-0.07)(+0.08) (stat.) +/- 0.05 (syst.) p
Determination of vertical bar V-cb vertical bar from the semileptonic decay B-0->D*(-)l(+)nu
No full textSemileptonic decays B --> D*(-)l(+)nu X were selected from a sample of 3.1 million hadronic Z decays collected by the DELPHI detector at LEP. A topological search for semileptonic B decays to resonant and non-resonant D*(-)pi(+) states was performed and the ratio of the branching fractions: Br(B --> D*(-)l(+)nu X)/Br(B --> D*(-)l(+)nu X) + Br(B-0 --> D*(-)l(+)nu) = 0.19 +/- 0.10(stat) +/- 0.06(syst) was determined. Taking into account this contribution, the differential decay width of B-0 --> D*(-)l(+)nu was measured as a function of the momentum transfer from the B to the D*(-) in two separate analyses, using exclusive and inclusive methods of D*(-) reconstruction. The distributions were fitted over the full momentum transfer range to extract the product of /V-cb/ times the normalization of the decay form factor F(q(max)(2)): F(q(max)(2))/V-cb/ = (35.4 +/- 1.9(stat) +/- 2.4(syst)) . 10(-3). The value of /V-cb/ was computed using theoretical calculations of F(q(max?2), giving: /V-cb/ = (38.9 +/- 2.0(stat) +/- 2.6(syst) +/- 1.7(theory)) . 10(-3). The total branching fraction Br(B-0 --> D*(-)l(-)nu) was determined to be: Br(B-0 --> D*(-)l(+)nu) = (5.52 +/- 0.17(stat) +/- 0.68(syst))%
PRODUCTION OF STRANGE B-BARYONS DECAYING INTO XI-/+-L-/+ PAIRS AT LEP
No full textAn excess of events containing, in a jet, a same-sign Xi(-/+) - l(-/+) pair as compared to those with an opposite-sign Xi(-/+) - l(-/+) pair has been observed in an analysis of 1.7 million hadronic Z(o) decays collected by the DELPHI detector at LEP between 1991 and 1993 inclusive. The probability for this signal to come from non B-baryon decays is less than 5 x 10(-4). The measured production fraction corresponds to: P(b --> B - baryon) x BR(B - baryon --> Xi(-) l(-) X) = (5.9 +/- 2.1 +/- 1.0) x 10(-4), per lepton species, averaged for electrons and muons and assuming the two channels have an equal contribution. Semileptonic decays of Lambda(b) baryons can account for less than 10% of these events and the major part of the signal has to originate from Xi(b) semileptonic decays, Using the subsample of these events where the Xi(-/+) trajectory has been measured in the Vertex Detector, the lifetime of B-baryons producing a Xi(-/+) in their semileptonic decay final state is found to be: tau(B - baryon --> Xi(-) l(-) X) = 1.5(-0.4)(+0.7) +/- 0.3 ps
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