202 research outputs found
Untersuchungen zur generellen Stressantwort von Bacillus subtilis nach Einwirkung von Umweltstress und bei niedriger Temperatur
Zusammenfassung
Der alternative Sigmafaktor SigB
kontrolliert die Expression des generellen Stressregulons in
Bacillus subtilis. Durch die Synthese von generellen
Stressproteinen werden nicht-wachsende B. subtilis-Zellen mit
einer unspezifischen, vielfÀltigen und vorsorgenden Resistenz
gegen zukĂŒnftigen Stress ausgestattet.
Um die Funktion der
generellen Stressantwort im Adaptationsnetzwerk dieses
Gram-positiven Modellorganismus besser zu verstehen, wurden die
VerÀnderungen im Transkriptom nach Einwirkung von Hitze, Salz
und Ethanolstress analysiert. Diese Studie wurde mit
DNA-Makroarrays durchgefĂŒhrt, auf die PCR-Produkte aller 4107
Gene gespottet waren. Insgesamt konnten 124 SigB-abhÀngige Gene
identifiziert werden. Darunter wurden 62 Gene neu dem
SigB-Regulon zugeordnet und 62 schon zuvor beschriebene
SigB-abhÀngige Gene bestÀtigt. Die genomweite Betrachtung des
Transkriptionsprofils nach Umweltstress erlaubte auch eine
Analyse der spezifischen Stressantworten von B. subtilis auf
Hitze-, Salz- und Ethanolstress. Neu war die Induktion des
ECF-Sigmafaktors SigW und seines Regulons nach 4% Salzstress.
In ?dot blot?-Experimenten konnte gezeigt werden,
dass die Induktion des SigW-Regulons osmotisch bedingt war.
AuĂerdem wurde die Induktion der generellen Stressantwort bei
niedriger Temperatur untersucht. Mit SigB-abhÀngigen LacZ- und
GFP-Reporterfusionen konnte der Induktionsverlauf des
SigB-Regulons in der KÀlte beobachtet werden. Bei 37 °C wird
das SigB-Regulon nach Umweltstress sofort, aber transient
induziert. In der KĂ€lte war dagegen eine langanhaltende
Induktion der ctc::lacZ-Reporterfusion in der exponentiellen
Phase zu sehen. Nach einem Maximum in der exponentiellen
Wachstumsphase fiel die Induktion bis zum Ăbergang in die
stationÀre Phase langsam wieder ab, um dann auf einem erhöhten
Level zu stagnieren.
Die Analyse verschiedener
Regulatormutanten der SigB-AktivitÀt bestÀtigte den
temperatursensitiven PhÀnotyp einer sigB-Mutante und
dokumentierte die Wachstumsdefekte einer rsbP-Mutante und einer
rsbUP-Mutante bei 15 °C, die vermutlich durch die schwache
Induktion des SigB-Regulons in diesen Zellen verursacht waren.
So stellte eine zusĂ€tzliche Deletion des Gens fĂŒr den
Anti-Antisigmafaktor RsbV in der rsbUP-Mutante die volle
Induktion der Reporterfusion wieder her, wodurch ebenfalls der
Wachstumsdefekt aufgehoben wurde. Die intensive, langanhaltende
Induktion des generellen Stressregulons in der
rsbUPV-Tripelmutante unterstĂŒtzt die These eines neuen
Signaltransduktionsweges zur Aktivierung von SigB in der KĂ€lte.
In weiteren Arbeiten wird zu klÀren sein, ob in die Aktivierung
von SigB in der KĂ€lte weitere Proteine einbezogen sind oder fĂŒr
die Aktivierung eine intrinsische InstabilitÀt des
RsbW/SigB-Komplexes verantwortlich ist
Schalten funktionalisierter, photochromer OberflÀchen mittels Organischer Leuchtdioden
This work describes the development of photo-switchable surfaces based on the two most common photochromic molecules. Additionally, these surfaces are excited with thin organic LEDs (OLEDs). With this combination an intelligent and programmable surface is realizable.
Here, a flexible PDMS copy of a lotus leaf covered with a single molecule layer of azobenzenes enables a 200 times higher relative transparency switching for a 355 nm laser beam compared to a flat glass substrate. Thereby a simple spatially resolved mapping of the azobenzene state on the surface becomes possible. A reversible contact angle switching between 138° and 95° is achieved with a non-covalently bound spiropyran layer on a candle soot surface. Then, a blue OLED is designed and fabricated that possesses a radiant flux of up to over 10 mW/cm2. It is used to switch both photochromic surfaces. With the aim to increase the switching speed, the light
outcoupling from OLEDs is enhanced. Tetrapodal zinc oxide particles are used to couple out trapped substrate modes. In order to use many OLEDs efficiently next to each other for the switching of a photochromic layer, it is necessary to direct the light
of their usually more Lambertian emitting profile. For this, optical gratings are integrated into OLEDs. Here, it is shown how the change of emitter position, refractive index contrast and absorption increase the resonances of these gratings. In addition,
grating effects on a fully flexible PDMS substrate are investigated and the first goniometric electroluminescene measurement of an OLED with an integrated multi-periodic grating is presented.Diese Arbeit beschreibt die Entwicklung von photoschaltbaren
Beschichtungen auf Basis der beiden gĂ€ngigsten photochromen MolekĂŒle. ZusĂ€tzlich werden diese Schichten mit organischen LEDs (OLEDs) angeregt. Durch diesen Integrationsschritt lĂ€sst sich eine âintelligenteâ und programmierbare OberflĂ€che erzeugen.
Eine mit einer einfachen Azobenzol-MolekĂŒl-Schicht versehene Kopie eines Lotusblattes aus flexiblem PDMS erlaubt hier ein um den Faktor 200 verstĂ€rktes Schalten der relativen Transmission eines Laserstrahles mit 355 nm WellenlĂ€nge gegenĂŒber einem glatten Glassubstrat, welches ebenfalls funktionalisiert wurde.
Dadurch wird eine einfache Kartierung der AzobenzolzustĂ€nde auf der OberflĂ€che möglich. Eine reversible Kontaktwinkelschaltung zwischen 138° und 95° wird mit nicht-kovalent aufgebrachten Spiropyranen auf KerzenruĂoberflĂ€chen erzielt. Im Anschluss wird eine blaue OLED designt und hergestellt, die eine Strahlungsleistung
von bis zu ĂŒber 10 mW/cm2 aufweist. Beide OberflĂ€chen werden mittels dieser OLED geschaltet. Mit dem Ziel einer Steigerung der Schaltgeschwindigkeit wird versucht, die Lichtauskopplung aus OLEDs zu erhöhen. FĂŒr die Auskopplung gefangener Substratmoden werden tetrapodale Zinkoxidpartikel verwendet. Um spĂ€ter möglichst
viele OLEDs unter einer photochromen Schicht nebeneinander betreiben zu können, ist es zudem notwendig, deren eher Lambertsches Abstrahlprofil zu richten. DafĂŒr eignen sich in OLEDs eingebrachte optische Gitter. Hier wird mittels verschiedener Experimente dargelegt, wie sich die Resonanzen der Gitter durch VerĂ€nderung von
Emitterposition, Brechungsindexkontrast und Absorption verstÀrken lassen. Des Weiteren wird der Gittereffekt in OLEDs auf flexiblen PDMS untersucht und zum ersten Mal eine goniometrische Elektrolumineszenzmessung einer OLED mit einem integrierten multiperiodischen Gitter gezeigt
Neue Perspektiven bei der UnkrautbekĂ€mpfung im Winterraps durch die EinfĂŒhrung des ClearfieldÂź-Systems
Winterraps ist eine der wichtigsten Ackerbaukulturen in Europa. Die Bedeutung dieser Ălfrucht nimmt seit Jahren zu. Um die ErtrĂ€ge zu sichern, ist eine verlĂ€ssliche Unkrautkontrolle unabdingbar. Wirkstoffbedingt wird diese zumeist im Vorauflauf der Kultur oder im Keimblattstadium der UnkrĂ€uter durchgefĂŒhrt, was oft auch mit dem Auflaufen des Rapses zusammen fĂ€llt. Unkrautdichten und damit Schadensschwellen können bei diesem frĂŒhen Einsatztermin nicht abgeschĂ€tzt werden. Breit wirksame, vertrĂ€gliche und im Nachauflaufeinsatz verwendbare Herbizide mit stabiler Wirkung unter den verschiedensten Boden- und Witterungsbedingungen wĂ€ren daher eine wĂŒnschenswerte Weiterentwicklung der Rapsanbausysteme. Mit der EinfĂŒhrung von Imidazolinon-tolerantem Winterraps in Europa sind diese Fortschritte mit einer zielgerichteten Unkrautkontrolle zu erreichen. Die wĂ€hrend der Entwicklung des ClearfieldÂź-Produktionssystems gesammelten Erfahrungen werden anhand mehrjĂ€hriger Zusammenfassungen sowie beispielhaft an verschiedenen Einzelergebnissen dargestellt. Insbesondere werden die Stetigkeit der Wirkung im Vergleich zu heutigen Standardherbiziden, sowie die BekĂ€mpfungsmöglichkeit von Ausfallgetreide und Kruziferen im Nachauflauf aufgezeigt.Stichwörter: ClearfieldÂź, Herbizidtoleranz, Imidazolinone, Stetigkeit, WinterrapsNew perspectives for weed control in winter oilseed rape due to the introduction of the ClearfieldÂź systemWinter oilseed rape is an increasingly important field crop in Europe. To safeguard yield, reliable and sustainable weed control systems are required. Weed control in oilseed rape today is based primarily on pre-emergence herbicides. Weed densities or threshold principles cannot be considered at this application timing. Postemergence herbicides with a broad spectrum and reliable efficacy over different soil and environmental conditions would be a desirable development for oilseed rape cultivation systems. The introduction of imidazolinone tolerant winter oilseed rape in Europe brings genuine improvement in weed control for oilseed rape. Accumulated experience during the development of the Clearfield Production System is demonstrated with multi year and exemplary single experiments. Of particular note, the reliability and consistency of the efficacy as compared to standard herbicides is outlined. The possibility of post-emergence control of crucifier weeds and the cross spectrum activity on volunteer cereals is demonstrated. Keywords: ClearfieldÂź, herbicide tolerance, imidazolinone, reliability, winter oilseed rap
Fluid fibres in true 3D ferroelectric liquids
We demonstrate an exceptional ability of a high-polarisation 3D ferroelectric
liquid to form freely-suspended fluid fibres at room temperature. Unlike fluid
threads in modulated smectics and columnar phases, where translational order is
a prerequisite for forming liquid fibres, recently discovered ferroelectric
nematic forms fibres with solely orientational molecular order. Additional
stabilisation mechanisms based on the polar nature of the mesophase are
required for this. We propose a model for such a mechanism and show that these
fibres demonstrate an exceptional non-linear optical response and exhibit
electric field-driven instabilities
Bacterial adaptation through distributed sensing of metabolic fluxes
We present a large-scale differential equation model of E. coli's central metabolism and its enzymatic, transcriptional, and posttranslational regulation. This model reproduces E. coli's known physiological behavior.We found that the interplay of known interactions in E. coli's central metabolism can indirectly recognize the presence of extracellular carbon sources through measuring intracellular metabolic flux patterns.We found that E. coli's system-level adaptations between glycolytic and gluconeogenic carbon sources are realized on the molecular level by global feedback architectures that overarch the enzymatic and transcriptional regulatory layers.We found that the capability for closed-loop self-regulation can emerge within metabolism itself and therefore, metabolic operation may adapt itself autonomously to changing carbon sources (not requiring upstream sensing and signaling)
Synthesis of organic liquid crystal containing selectively fluorinated cyclopropanes
Authors thank the Chinese Scholarship Council for a studentship (ZF) and the EPSRC Mass Spectroscopy Service at Swansea for analysis.This paper describes the synthesis of a series of organic liquid crystals (LC) containing selectively fluorinated cyclopropanes at their termini. The syntheses used difluorocarbene additions to olefin precursors, an approach which proved straightforward such that these liquid crystal candidates could be efficiently prepared. Their physical and thermodynamic properties were evaluated and depending on individual structures, they either displayed positive or negative dielectric anisotropy. The study gives some guidance into effective structure property relationships for the design of LCs containing selectively fluorinated cyclopropane motifs.Publisher PDFPeer reviewe
3D-printed rotating spinnerets create membranes with a twist
Round hollow fiber membranes are long-established in applications such as gas
separation, ultrafiltration and blood dialysis. Yet, it is well known that
geometrical topologies can introduce secondary ow patterns counteracting mass
transport limitations, stemming from diffusion resistances and fouling. We
present a new systematic method- ology to fabricate novel membrane
architectures. We use the freedom of design by 3D-printing spinnerets, having
multiple bore channels of any geometry. First, such spinnerets are stationary
to fabricate straight bore channels inside a monolithic membrane. Second, in an
even more complex design, a new mechanical system enables rotating the
spinneret. Such rotating multibore spinnerets enable (A) the preparation of
twisted channels inside a porous monolithic membrane as well as (B) a helical
twist of the outside geometry. The spun material systems comprise classical
polymer solutions as well as metal-polymer slurries resulting in solid porous
metallic monolithic membrane after thermal post-processing. It is known that
twisted spiral-type bore channel geometries are potentially superior over
straight channels with respect to mass and heat polarization phenomena, however
their fabrication was cumber- some in the past. Now, the described methodology
enables membrane fabrication to tailor the membrane geometry to the needs of
the membrane process
Not again! Effect of previous test results, age group and reason for testing on (re-)infection with Chlamydia trachomatis in Germany
Background:
Infection with Chlamydia trachomatis (Ct) is the most commonly reported sexually transmitted infection in Europe. In Germany, Ct screening is offered free of charge to pregnant women since 1995 and to women <â25 years of age since 2008. For symptomatic individuals, testing is covered by statutory health insurance. Study results have shown that repeat Ct infection occurs in 10â20% of previously infected women and men. Our aim was to describe persons tested for Ct and to investigate the determinants of (repeat) Ct infection in women and men in Germany.
Methods:
We analysed Ct test results from men and women tested between 2008 and 2014 in laboratories participating in the German Chlamydia trachomatis Laboratory Sentinel surveillance. Reinfection was defined as at least 2 positive laboratory tests within more than 30 days. We performed logistic regression stratified by sex and, for women, reason for testing to determine the effect of previous test results and age group on subsequent test results.
Results:
In total, 2,574,635 Ct tests could be attributed to 1,815,494 women and 123,033 men. 5% of women and 14% of men tested positive at least once. 15â19- and 20â24-year-old women tested positive at least once respectively in 6.8 and 6.0%, while men respectively in 16.6 and 21.2%. Altogether, 23.1% of tested women and 11.9% of tested men were tested repeatedly between 2008 and 2014. Among those who previously tested positive, reinfection occurred in 2.0% of women and 6.6% of men. Likelihood to be tested Ct positive was higher in women and men with a positive Ct test in the past compared to previously tested Ct negative, odds ratios 4.7 and 2.6 (pâ<â0.01) respectively. Odds ratios ranged by age group and test reason.
Conclusion:
A history of Ct infection increased the likelihood of infection with Ct in women and men taking into account the result of the previous test. Health education, safer sex and treatment of partners are necessary for women and men who have tested positive to prevent reinfection and complications and to interrupt the chain of transmission. To identify potential reinfection repeat testing after treatment should be performed.Peer Reviewe
The impact of regional socioeconomic deprivation on the timing of HIV diagnosis: a cross-sectional study in Germany
Background:
HIV infections which are diagnosed at advanced stages are associated with significantly poorer health outcomes. In Germany, the proportion of persons living with HIV who are diagnosed at later stages has remained continuously high. This study examined the impact of regional socioeconomic deprivation on the timing of HIV diagnosis.
Methods:
We used data from the national statutory notification of newly diagnosed HIV infections between 2011 and 2018 with further information on the timing of diagnosis determined by the BED-Capture-ELISA test (BED-CEIA) and diagnosing physicians. Data on regional socioeconomic deprivation were derived from the German Index of Socioeconomic Deprivation (GISD). Outcome measures were a non-recent infection based on the BED-CEIA result or an infection at the stage of AIDS. The effect of socioeconomic deprivation on the timing of diagnosis was analysed using multivariable Poisson regression models with cluster-robust error variance.
Results:
Overall, 67.5% (nâ=â10,810) of the persons were diagnosed with a non-recent infection and 15.2% (nâ=â2746) with AIDS. The proportions were higher among persons with heterosexual contact compared to men who have sex with men (MSM) (76.8% non-recent and 14.9% AIDS vs. 61.7% non-recent and 11.4% AIDS). MSM living in highly deprived regions in the countryside (<â100 k residents) were more likely to have a non-recent infection (aPR: 1.16, 95% CI: 1.05â1.28) as well as AIDS (aPR: 1.41, 95% CI: 1.08â1.85) at the time of diagnosis compared to MSM in less deprived regions in the countryside. No differences were observed among MSM from towns (100 kââ€â1 million residents) or major cities (â„â1 million residents), and no differences overall in the heterosexual transmission group.
Conclusions:
An effect of socioeconomic deprivation on the timing of HIV diagnosis was found only in MSM from countryside regions. We suggest that efforts in promoting HIV awareness and regular HIV testing are increased for heterosexual persons irrespective of socioeconomic background, and for MSM with a focus on those living in deprived regions in the countryside.Peer Reviewe
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