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Rumbaugh KP 《Analytical and bioanalytical chemistry》2007,387(2):425-435
Most living organisms possess sophisticated cell-signaling networks in which lipid-based signals modulate biological effects
such as cell differentiation, reproduction and immune responses. Acyl homoserine lactone (AHL) autoinducers are fatty acid-based
signaling molecules synthesized by several Gram-negative bacteria that are used to coordinate gene expression in a process
termed “quorum sensing” (QS). Recent evidence shows that autoinducers not only control gene expression in bacterial cells,
but also alter gene expression in mammalian cells. These alterations include modulation of proinflammatory cytokines and induction
of apoptosis. Some of these responses may have deleterious effects on the host’s immune response, thereby leading to increased
bacterial pathogenesis. Prokaryotes and eukaryotes have cohabited for approximately two billion years, during which time they
have been exposed to each others’ soluble signaling molecules. We postulate that organisms from the different kingdoms of
nature have acquired mechanisms to sense and respond to each others signaling molecules, and we have named this process interkingdom
signaling. We further propose that autoinducers, which exhibit structural and functional similarities to mammalian lipid-based
hormones, are excellent candidates for mediating this interkingdom communication. Here we will compare and contrast bacterial
QS systems with eukaryotic endocrine systems, and discuss the mechanisms by which autoinducers may exploit mammalian signal
transduction pathways. 相似文献
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John Asplund Gregory Clark Garner Cochran va Czabarka Arran Hamm Gwen Spencer Lszl Szkely Libby Taylor Zhiyu Wang 《组合设计杂志》2019,27(10):586-597
The crossing number of a graph is the smallest number of edge crossings over all drawings of in the plane. For any , the ‐planar crossing number of , is defined as the minimum of over all graphs with . Pach et al [Comput. Geom.: Theory Appl. 68 (2018), pp. 2–6] showed that for every , we have and that this bound does not remain true if we replace the constant by any number smaller than . We improve the upper bound to as . For the class of bipartite graphs, we show that the best constant is exactly for every . The results extend to the rectilinear variant of the ‐planar crossing number. 相似文献
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Arran R. Wood Nicolas Benedetto Nigel Hooker Edward Scullion Paul A. Smith John F. Watts 《Surface and interface analysis : SIA》2008,40(10):1409-1414
The design philosophy and implementation of an ultra high vacuum (UHV), PC controlled, automated in situ fracture stage for a surface analysis system is described. ToF‐SIMS spectra are shown to illustrate the improvement in spectral quality obtained from micro‐compact tension (CT) tests of polymer matrix fracture surfaces produced using the fracture stage in UHV compared to those obtained from a sample tested at air. This system is flexible in that by changing the capacity of the load cell it is possible to reduce or increase maximum loads as the specimen type and material demands. The stage has been designed with instrumental flexibility in mind, utilising commercial SEM‐stub type sample mounts, and can thus be used for AES/SAM and XPS investigations, as well as ToF‐SIMS analysis, in the authors' laboratory. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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Fiddy SG Evans J Neisius T Newton MA Tsoureas N Tulloch AA Danopoulos AA 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(13):3652-3659
A study on the Mizoroki-Heck coupling of selected aryl bromides with acrylates catalysed by a series of Pd complexes of bidentate pyridyl-, picolyl-, diphenylphosphinoethyl- and diphenylphosphinomethyl-functionalised N-heterocyclic carbene (NHC) is reported. The observed activity is dependent on the type of solvent and base used and the nature of the "classical" donors of the mixed-donor bidentate ligand and its bite angle. A mechanistic model is presented for the pyridine-functionalised NHC complexes based on an in situ EXAFS study under dilute catalyst conditions (2 mM Pd). The model involves pre-dissociation of the pyridine functionality and oxidative addition of ArBr in the early stages of the reaction, as well as formation of monomeric and dimeric Pd species at the time of substrate conversion. 相似文献
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Bell NJ Cox AJ Cameron NR Evans JS Marder TB Duin MA Elsevier CJ Baucherel X Tulloch AA Tooze RP 《Chemical communications (Cambridge, England)》2004,(16):1854-1855
Bis-pinacolatodiboron reacts with [small alpha],[small beta]-unsaturated carbonyl compounds to give 1,4- and unprecedented 3,4-additions in the presence of a second generation Pt(0) catalyst at ambient temperature. 相似文献
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Sven Kleinhenz Arran A. D. Tulloch Andreas A. Danopoulos 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(10):e476-e476
The structure of the title compound, C13H18N3+·Br?·H2O, shows that the cation and the bromide anion are linked via the water molecule through weak intermolecular hydrogen bonds. The water was not detected by NMR spectroscopy, but the cell content is in agreement with the elemental analysis. The presence of water plays an important role in further reactions. 相似文献
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