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811.
Manon Laporte Valerie Raeymaekers Ria Van Berwaer Julie Vandeput Isabel Marchand-Casas Hendrik-Jan Thibaut Dominique Van Looveren Katleen Martens Markus Hoffmann Piet Maes Stefan Phlmann Lieve Naesens Annelies Stevaert 《PLoS pathogens》2021,17(4)
The high transmissibility of SARS-CoV-2 is related to abundant replication in the upper airways, which is not observed for the other highly pathogenic coronaviruses SARS-CoV and MERS-CoV. We here reveal features of the coronavirus spike (S) protein, which optimize the virus towards the human respiratory tract. First, the S proteins exhibit an intrinsic temperature preference, corresponding with the temperature of the upper or lower airways. Pseudoviruses bearing the SARS-CoV-2 spike (SARS-2-S) were more infectious when produced at 33°C instead of 37°C, a property shared with the S protein of HCoV-229E, a common cold coronavirus. In contrast, the S proteins of SARS-CoV and MERS-CoV favored 37°C, in accordance with virus preference for the lower airways. Next, SARS-2-S-driven entry was efficiently activated by not only TMPRSS2, but also the TMPRSS13 protease, thus broadening the cell tropism of SARS-CoV-2. Both proteases proved relevant in the context of authentic virus replication. TMPRSS13 appeared an effective spike activator for the virulent coronaviruses but not the low pathogenic HCoV-229E virus. Activation of SARS-2-S by these surface proteases requires processing of the S1/S2 cleavage loop, in which both the furin recognition motif and extended loop length proved critical. Conversely, entry of loop deletion mutants is significantly increased in cathepsin-rich cells. Finally, we demonstrate that the D614G mutation increases SARS-CoV-2 stability, particularly at 37°C, and, enhances its use of the cathepsin L pathway. This indicates a link between S protein stability and usage of this alternative route for virus entry. Since these spike properties may promote virus spread, they potentially explain why the spike-G614 variant has replaced the early D614 variant to become globally predominant. Collectively, our findings reveal adaptive mechanisms whereby the coronavirus spike protein is adjusted to match the temperature and protease conditions of the airways, to enhance virus transmission and pathology. 相似文献
812.
813.
Veniero Lenzi Piet J. Driest Dirk J. Dijkstra Marta M. D. Ramos Luis S. A. Marques 《Molecular simulation》2019,45(3):207-214
Aliphatic diisocyanates and their derivatives are key liquid components in the industrial processing of polyurethane materials. In particular, for the synthesis of crosslinked polyurethane materials, the higher functionality molecules obtained by reacting three -or more- diisocyanates are of interest. However, despite their widespread application, the relation between molecular structure and macroscopic physical properties, in particular viscosity, is poorly understood in these systems. In this work, we introduce a new force field parameter set, GAFF-IC, based on the widely-used and versatile GAFF force field, meant for accurate predictions of physical properties of isocyanate-based molecular liquids. The new parameters allow to predict the vaporization enthalpies and densities of several isocyanate-based molecules, which are found in excellent agreement with the available experimental data. The effectiveness and transferability of the improved parameters is verified by calculating the viscosities of several isocyanates, isocyanate dimers (uretdiones) and isocyanate trimers (isocyanurates), resulting in accurate viscosity predictions in excellent agreement with experimental values. 相似文献
814.
815.
Stefanie J.W.H. Oude Elferink Piet N.L. Lens Cor Dijkema Alfons J.M. Stams 《FEMS microbiology letters》1996,142(2-3):237-241
Abstract The isomerization of butyrate and isobutyrate was investigated for the sulfate reducer Desulforhabdus amnigenus . Nuclear magnetic resonance (NMR) studies with 13 C-labelled butyrate showed that isobutyrate was formed by migration of the carboxyl group, in conformity with the butyrate isomerization reaction reported for methanogenic consortia. In addition to D. amnigenus , several other butyrate-degrading sulfate reducers ( Desulfobacterium vacuolatum, Desulfoarculus baarsii and Desulfotomaculum sp.) were capable of butyrate isomerization. 相似文献
816.
We studied the combined effect of fish kairomones and food conditions on the relative tail spine length (RTL) of five Daphnia taxa, and the interaction of these factors with the vertical distribution of the daphnids. The experiment was done in two large-scale indoor containers, the so-called plankton towers in Plön, Germany. We conducted a competition experiment in which food level and the presence of fish chemicals and later fish were varied. A strong response of RTL to fish kairomones (e.g., longer tail spines), significant differences in RTL between species, but no differences in RTL with water depth were found. Further, we observed that these Daphnia taxa produced a higher RTL only under high food conditions. This suggests that there is a cost related to the production of longer tail spines.In a preliminary study in lake Plußsee, we found that Daphnia had longer average RTL than in the towers. Further, we noted significant differences in RTL between the two sampling dates, which may be related to a lower food level. We also detected a strong inverse correlation between RTL and depth. We discuss the implications of these findings for the co-existence of co-occurring Daphnia species and their hybrids. 相似文献
817.
818.
Apollo Pronk Piet Leguit Arthur A. G. M. Hoynck van Papendrecht Edwin Hagelen Theo J. M. V. van Vroonhoven Henri A. Verbrugh 《In vitro cellular & developmental biology. Animal》1993,29(2):127-134
Summary Normal human mesothelial cells (NHMC) were isolated from pieces of human omentum. The cell yield was approximately one million
cells per square centimeter omentum. The mesothelial cells were identified by their positive staining with monoclonal antibodies
against cytokeratins 6 and 18. Transmission electronmicroscopy of cultured NHMC revealed many microvilli on the apical surface
and many mitochondria and pinocytotic vesicles in the cytoplasm, indicating active transmembrane transport. Growth of NHMC
was directly related to the concentration of human serum or of fetal bovine serum in the growth medium. Addition of epidermal
growth factor with or without hydrocortisone resulted in a significant increase of NHMC growth; when endothelial cell growth
factor, insulin, or hydrocortisone were added no such increase was observed. Seeding NHMC at densities less than 3000/cm2 did not result in monolayer formation. The mesothelial cells were serially passed in growth medium M199 with added 10% fetal
bovine serum up to 7 passages. However, after Passage 4 the cells changed into giant cells with an irregular pattern, and
a lack of intracellular cytokeratin expression was observed for most of the cells. 相似文献
819.
820.
Individuals of many species differ consistently in their behavioralreaction to mild novel challenges. Suites of these behaviorsare referred to as behavioral syndromes or personalities. Personalitytraits are often phenotypically and genetically correlated.Therefore, animal personalities are generally considered asbroad characteristics, with one underlying genetical and physiologicalmechanism that is expressed across situations and contexts.Because there are carryover effects between situations, animalsare not entirely flexible in their behavior in each situation.This may cause behaviors to seem nonadaptive in isolated situations.To test whether individuals with different personalities couldreact differently to changes in their environment, we studiedcontext dependence of personalities in the great tit (Parusmajor). We tested birds categorized as either fast or slow explorersfor their latency to come back to a feeding table after a mildstartle (risk-taking behavior) in a nonsocial followed by asocial context. We found that the relation between exploratorybehavior and risk-taking behavior depended on the social context.Females in general returned later in the social test, whilemale reaction to the presence of a conspecific was dependenton their behavioral type. Slow males thereby reacted to thebehavior of the companion and fast males did not. These resultsshow that although personalities have a rigid structure therelation between personality traits is context dependent. Theseresults are discussed in the perspective of the adaptive significanceand maintenance of personalities. 相似文献