101,443 research outputs found
Heterogenität in der Sekundarstufe II. Einleitende Bemerkungen zum Thema
No full textRosowski E, Stroot T, Boller S. Heterogenität in der Sekundarstufe II. Einleitende Bemerkungen zum Thema. In: Boller S, Rosowski E, Stroot T, eds. Heterogenität in Schule und Unterricht. Handlungsansätze zum Pädagogischen Umgang mit Vielfalt. Oberstufen-Kolleg des Landes Nordrhein-Westfalen Pädagogik. Weinheim: Beltz; 2007: 12-20
Heterogene Bildungslaufbahnen als Herausforderung für Beratung und Förderung in der Sekundarstufe II
No full textRosowski E, Boller S. Heterogene Bildungslaufbahnen als Herausforderung für Beratung und Förderung in der Sekundarstufe II. In: Boller S, Rosowski E, Stroot T, eds. Heterogenität in Schule und Unterricht. Handlungsansätze zum Pädagogischen Umgang mit Vielfalt. Oberstufen-Kolleg des Landes Nordrhein-Westfalen Pädagogik. Weinheim: Beltz; 2007: 90-102
Map of localities to accompany "Among the Indians."
No full textScale approximately 1:3,686,4001 map ; 31 x 49 cm, on sheet 36 x 51 cmMap removed from Henry A. Boller's "Among the Indians : eight years in the far west: 1858-1866 ; embracing sketches of Montana and Salt Lake."Map repaired following removal from book.Relief shown by hachures
Heterogenität in Schule und Unterricht. Handlungsansätze zum pädagogischen Umgang mit Vielfalt
No full textBoller S, Rosowski E, Stroot T, eds. Heterogenität in Schule und Unterricht. Handlungsansätze zum pädagogischen Umgang mit Vielfalt. Pädagogik. Weinheim u.a.: Beltz; 2007
Innate immunity mediated by the flagellin receptor FLS2 in Arabidopsis and tomato : a molecular approach to characterize ligand binding and function, using receptor chimeras
No full textFlagellin, the major subunit of the bacterial motility organ flagellum is an archetypical elicitor molecule perceived by a variety of plant species (Felix et al., 1999). Flg22, a synthetic peptide comprising the highly conserved amino acid residues of the flagellin N-terminus, has been shown to be the active epitope of flagellin which is recognized by plants and sufficient to activate plant defense responses (Felix et al., 1999). Flagellin/flg22 recognition has been attributed to a single protein, FLS2. FLS2 is a leucine rich repeat (LRR) receptor like kinase (RLK), consisting of 28 extracellular LRRs, a single transmembrane domain and an intracellular ser/thr kinase domain, was first identified in the model plant Arabidopsis thaliana (Gómez-Gómez and Boller, 2000) and shown to directly bind flg22 (Chinchilla et al., 2006). Meanwhile, orthologues of FLS2 have been identified in a variety of species from different families, among them tomato (Lycopersicon esculentum), Nicotiana benthamiana, Ricinus communis and Populus trichocarpa, to name just a few (Robatzek et al., 2007b). Although all these plants recognize flg22 as an elicitor, distinct species specific differences were identified. In this work, the molecular differences between the flagellin recognition systems of Arabidopsis (AtFLS2) and tomato (LeFLS2) are analyzed in depth. It was shown that full length flg22 is required for activity in Arabidopsis while tomato requires only the 15 aa peptide flg15 for full stimulation of defense responses (Meindl et al., 2000). Receptor activation of FLS2 by flg22 occurs according to the address-message concept with binding of the address as a first step, and message-induced receptor activation as a second step (Meindl et al., 2000). By using a variety of flg22-derivatives, we analyze how Arabidopsis and tomato flagellin receptors discriminate between different variants of flg22 in terms of binding and receptor activation. By using the species specific differences of Arabidopsis and tomato flagellin perception, we identify areas within the LRR domain of the respective flagellin receptors which are responsible for interaction with the ligand. To achieve this, we constructed a series of chimeric receptors by swapping different parts of the LRR domain from LeFLS into the AtFLS2 sequence. These chimeric receptors were transformed into Nicotiana benthamiana and Arabidopsis thaliana and the transformed plants were tested for receptor function using various bioassays such as ethylene production and growth inhibition and we performed binding assays using immunoprecipitated receptors. Based on these experiments we show that the LeLRR 1 to 10 are sufficient to bind the minimum peptide flg15-Δ7, the shortest flg22-derivative perceived by tomato consisting only of the central 8 amino acids of flg22. We show that the initial ten N-terminal LRRs between the amino acids 32-337 and within this area, especially the amino acids 236-337 are import for the higher affinity of LeFLS2 to flg22 and N-terminally truncated flg22-derivatives. We further show that an additional region between the LRR 19 to 24 of LeFLS2 is involved in the recognition of the C-terminus of flg22. Because the C-terminus of flg22 has been shown to be part of the “message”, which activates receptor signaling (Meindl et al., 2000; Chinchilla et al., 2006), we propose the region of LRR 19 to 24 to be play an important role for activation of FLS2. Additionally a
chimeric receptor between AtFLS2 and LeFLS2 is presented which shows the characteristics of a constitutive active FLS2 allele when transformed into Arabidopsis. Interestingly, the constitutive signaling of this chimeric receptor can only be triggered via the artificial extracellular LRR domain, since the complete intracellular receptor part, e.g. transmembrane- juxtamembrane- and kinasedomain is not affected from the LRR domain swapping. Together, this study provides new insight towards the understanding of FLS2-ligand interaction and an interesting tool to further study receptor activation
Letter, [Author unclear] to Paulina T. Merritt
No full textHandwritten letter to Paulina Merritt from an unknown author, October 1, 1876.
Soft X-ray properties of a spectroscopically selected sample of interacting and isolated Seyfert galaxies
No full textWe present a catalogue of ROSAT detected sources in the sample of spectroscopically selected Seyfert 1 and Seyfert 2 galaxies of Rafanelli et al. (\cite{Rafanelli95}). The catalogue contains 102 Seyfert 1 and 36 Seyfert 2 galaxies. The identification is based on X-ray contour maps overlaid on optical images taken from the Digitized Sky Survey. We have derived the basic spectral and timing properties of the X-ray detected Seyfert galaxies. For Seyfert 1 galaxies a strong correlation between photon index and X-ray luminosity is detected. We confirm the presence of generally steeper X-ray continua in narrow-line Seyfert 1 galaxies (NLS1s) compared to broad-line Seyfert 1 galaxies. Seyfert 2 galaxies show photon indices similar to those of NLS1s. Whereas a tendency for an increasing X-ray luminosity with increasing interaction strength is found for Seyfert 1 galaxies, such a correlation is not found for Seyfert 2 galaxies. For Seyfert 1 galaxies we found also a strong correlation for increasing far-infrared luminosity with increasing interaction strength. Both NLS1s and Seyfert 2 galaxies show the highest values of far-infrared luminosity compared to Seyfert 1 galaxies, suggesting that NLS1s and Seyfert 2 galaxies host strong (circumnuclear) star formation. For variable Seyfert galaxies we present the X-ray light curves obtained from the ROSAT All-Sky Survey and from ROSAT PSPC and HRI pointed observations. Besides the expected strong short- and long-term X-ray variability in Seyfert 1 galaxies, we find indications for X-ray flux variations in Seyfert 2 galaxies. All overlays can be retrieved via CDS anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)} or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/368/79
Effects of chitinase and ß-1, 3 glucanase from pea on the growth of saprophytic, pathogenic and mycorrhizal fungi.
No full textXMM-Newton observation of Mrk 110
No full textContext.We report on the first XMM-Newton observation of the bright
narrow-line Seyfert 1 galaxy Mrk 110.
Aims.Our analysis is aimed to study the properties of the X-ray spectrum of Mrk 110
and compare them with those inferred from optical spectroscopy.
Methods.We make use of detailed timing and spectral analysis as well as high resolution
X-ray spectroscopy with the XMM-Newton gratings.
Results.We find a narrow Fe K fluorescent line,
a broad component (16 500 km s-1) of the O VII triplet,
either due to infall motions or gravitational redshift effects in the vicinity
of the central black hole, a Comptonized accretion disk layer, and a strong starburst component.
Conclusions.We found that Mrk 110 has a complex X-ray spectrum, exhibiting
relatively strong broadening of the O VII emission line, probably associated with X-ray emission
from the Broad Line Region (BLR), which might be correlated with the optical gravitationally redshifted,
asymmetric line profiles.
Spectral fits including a Gaussian line or a discline give
the same statistical significance. If the broad redshifted soft X-ray components are due to gravitational
redshift effects, the distance of the line-emitting regions ranges between about 0.2 and 1 light day with
respect to the central black hole.
In addition, the EPIC pn spectrum shows a double power-law and a strong starburst component. One power-law
component exhibits a photon index slope of , while the second is much steeper with
a power law slope of . The second power-law is most probably due to thermal
Comptonization of a hot electron layer above the accretion disk.
Mrk 110 is another example of extragalactic
sources showing Comptonization effects in the accretion disc and its properties are very similar to
the narrow-line Seyfert 1 Galaxy Ton S 180
Characterization of flagellin perception in "Arabidopsis thaliana"
No full textAt the time when this work was started, a highly sensitive perception system for bacterial flagellin in plant cells had been described (Felix et al, 1999), and FLS1 and FLS2, had been identified in A. thaliana as essential loci for flagellin perception (Gómez-Gómez et al, 1999; Gómez-Gómez and Boller, 2000). In addition, radioactive binding studies had been established for tomato to characterize the flagellin binding site (Meindl et al, 2000). It became necessary to establish binding studies for A. thaliana as well, in order to assess if mutations in FLS2, causing insensitivity to flagellin, correlated with impairment in binding. Beyond the biochemical characterization of the flagellin binding site in A. thaliana, the goal of this work was to find out if the putative flagellin receptor FLS2 is the flagellin binding site. The A. thaliana flagellin binding site was found to exhibit the biochemical characteristics of a bona fida flagellin receptor: Binding was saturable and exhibited high affinity. It exhibited specificity for flagellin-derived peptides with biological activity as agonists or antagonists of the elicitor responses. Activation of flagellin receptor in A. thaliana appeared to occur as a two step process according to the addressmessage concept with the N-terminal part required for binding (address) and the Cterminal part for activation (message), as proposed for tomato before (Meindl et al, 2000). Additionally, sensitivity to salt and pH were determined, and reversibility was found to increase during cell fractionation, indicating that disassembly of a receptor complex or loss of cofactors take place. Furthermore, it was concluded that the flagellin binding site is localized at the plasma membrane. Comparison between the characteristics of flagellin binding in A. thaliana and tomato revealed that they show clear overall similarity but exhibit characteristic differences in detail, for instance in specificity, reversibility and sensitivity to pH and salts. The elution pattern from the ion exchange column indicated that two subclasses of the binding site occur. Concanavalin A chromatography showed, that the binding site is glycosylated, and optimization of ligand affinity chromatography paved the way for the identification of the binding site in future. Binding assays in extracts of different ecotypes and La-er FLS2 mutants showed a tight
correlation between the presence of the binding site and sensitivity to flagellin,
providing further evidence that the characterized binding site acts as the physiological
receptor. Moreover, these results showed the pivotal role of FLS2 for flagellin binding.
One mutation causing impairment of flg22 binding was localized in the LRR domain,
indicating that this site might be involved in direct flagellin binding. Surprisingly, four
mutations that disrupted binding, affected the cytoplasmic kinase domain. The
significance of this finding is not understood yet. We speculated that the kinase activity
might be important for proper targeting of FLS2 or for formation of a functional
receptor complex.
In order to prove that FLS2 is the flagellin binding site, epitope-tagged FLS2 was
introduced into A. thaliana and tomato cell cultures and plants. When introduced into
fls2 mutants, this construct complemented the mutation. However, properties of
FLS2:myc protein, detected by immuno blot techniques, clearly differed from the
properties of the flagellin binding site. Nevertheless, specificity of FLS2:myc transgenic
tomato cell cultures for flagellin-derived peptides carried characteristic traits of A.
thaliana binding and elicitor-response. This finding suggests that FLS2 determines
specificity of flagellin perception. Another interesting aspect of this finding is that FLS2
seems compatible with tomato signal transduction components. It will be interesting to
find out which part of FLS2 is responsible for the differences of flagellin perception,
and which part is conserved in the two species.
Although the results presented in this work clearly demonstrate an essential role of
FLS2 for flagellin binding, direct evidence that FLS2 is the flagellin binding site is still
lacking. Binding studies with heterologously expressed FLS2 could contribute to
clearing this point. Also, optimization of the experimental conditions in order to prove
flagellin binding by solubilized FLS2 could be reasonable. Alternatively, purification of
the flagellin binding site would represent an independent approach. This method, like
partial purification of FLS2, could provide further information’s about additional
components of the receptor complex. It is likely that several components are needed for
flagellin perception, as found for the CLAVATA and the self-incompatibility perception
systems (for review see introduction)
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