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251.
Enantiomerization of Allylic Trifluoromethyl Sulfoxides Studied by HPLC Analysis and DFT Calculations 下载免费PDF全文
Laetitia Bailly Emilie Petit Mayaka Maeno Norio Shibata Oliver Trapp Pascal Cardinael Isabelle Chataigner Dominique Cahard 《Chirality》2016,28(2):136-142
Enantiomerization of allylic trifluoromethyl sulfoxides occurs spontaneously at room temperature through the corresponding allylic trifluoromethanesulfenates via a [2,3]‐sigmatropic rearrangement. Dynamic enantioselective high‐performance liquid chromatography (HPLC) analysis revealed the stereodynamics of these sulfoxides ranging from chromatographic resolution to peak coalescence at temperatures between 5 and 53 °C. The rate constant of enantiomerization and activation parameters were determined and compared with Density Functional Theory (DFT) calculations. Chirality 28:136–142, 2016. © 2015 Wiley Periodicals, Inc. 相似文献
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Coeytaux E Coulaud D Le Cam E Danos O Kichler A 《The Journal of biological chemistry》2003,278(20):18110-18116
Viral protein R (Vpr) is a small protein of 96 amino acids that is conserved among the lentiviruses human immunodeficiency virus type 1 (HIV-1), HIV-2, and simian immunodeficiency virus. We recently sought to determine whether the karyophilic properties of Vpr, as well as its ability to bind nucleic acids, could be used to deliver DNA into cells. We have found that the C-terminal domain of Vpr-(52-96) is able to efficiently transfect various cell lines. Here, we show that the shortest active sequence for gene transfer corresponds to the domain that adopts a alpha-helix conformation. DNA binding studies and permeabilization assays performed on cells demonstrated that the peptides that are efficient in transfection condense plasmid DNA and are membranolytic. Electron microscopy studies and transfection experiments performed in the presence of inhibitors of the endocytic processes indicated that the major entry pathway of Vpr-DNA complexes is through endocytosis. Taken together, the results show that the cationic C-terminal alpha-helix of Vpr has DNA-condensing as well as membrane-destabilizing capabilities, both properties that are indispensable for efficient DNA transfection. 相似文献
254.
Marie-Laure Yaspo Nathalie Crété Zoubida Chettouh Jean-Louis Blouin Zohra Rahmani Dominique Stehelin Pierre-Marie Sinet Nicole Créau-Goldberg Jean-Maurice Delabar 《Human genetics》1992,90(4):427-434
To generate new chromosome 21 markers in a region that is critical for the pathogenesis of Down syndrome (D21S55-MX1), we used pulsed field gel electrophoresis (PFGE) to isolate a 600-kb NruI DNA fragment from the WA17 hybrid cell line, which has retained chromosome 21 as the only human material. This fragment, which contains the oncogene ETS2, was used to construct a partial genomic library. Among the 14 unique sequences that were isolated, 3 were polymorphic markers and contained sequences that are conserved in mammals. Five of these markers mapped on the ETS2-containing NruI fragment and allowed us to define an 800-kb high-resolution PFGE map. 相似文献
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Nacher M Singhasivanon P Silachamroon U Treeprasertsuk S Tosukhowong T Vannaphan S Gay F Mazier D Looareesuwan S 《The Journal of parasitology》2002,88(1):97-101
To determine factors influencing gametocyte carriage, a cross-sectional study was conducted among 512 patients admitted for Plasmodium falciparum malaria. After adjustments for potential confounders, hemoglobin concentrations were lower in gametocyte carriers 10.5 (+/-2.5) than in patients without gametocytes 12.5 (+/-2.3) (P < 0.0001). Hemoglobin concentrations were negatively correlated with peak gametocyte counts (Spearman's p = -0.37, P < 0.0001) and gametocyte carriage durations (Spearman's p = -(0.30, P < 0.0001). Adjustments for the duration of the malaria episode and other potential confounders did not alter the association (P < 0.0001). After adjustment for potential confounders, the median asexual parasitemia was higher in patients with gametocytes than in patients without gametocytes (P = 0.003). Severe malaria cases were more likely to have gametocytes (65%) than malaria with hyperparasitemia (38%) or mild malaria (31%) (P = 0.0001). These findings suggest that events surrounding anemia and tissue hypoxia stimulate Plasmodium falciparum gametocytogenesis. 相似文献
257.
How life‐history traits affect ecosystem properties: effects of dispersal in meta‐ecosystems 下载免费PDF全文
François Massol Florian Altermatt Isabelle Gounand Dominique Gravel Mathew A. Leibold Nicolas Mouquet 《Oikos》2017,126(4):532-546
The concept of life‐history traits and the study of these traits are the hallmark of population biology. Acknowledging their variability and evolution has allowed us to understand how species adapt in response to their environment. The same traits are also involved in how species alter ecosystems and shape their dynamics and functioning. Some theories, such as the metabolic theory of ecology, ecological stoichiometry or pace‐of‐life theory, already recognize this junction, but only do so in an implicitly non‐spatial context. Meanwhile, for a decade now, it has been argued that ecosystem properties have to be understood at a larger scale using meta‐ecosystem theory because source–sink dynamics, community assembly and ecosystem stability are all modified by spatial structure. Here, we argue that some ecosystem properties can be linked to a single life‐history trait, dispersal, i.e. the tendency of organisms to live, compete and reproduce away from their birth place. By articulating recent theoretical and empirical studies linking ecosystem functioning and dynamics to species dispersal, we aim to highlight both the known connections between life‐history traits and ecosystem properties and the unknown areas, which deserve further empirical and theoretical developments. 相似文献
258.
AMPKα1‐LDH pathway regulates muscle stem cell self‐renewal by controlling metabolic homeostasis 下载免费PDF全文
Marine Theret Gaëtan Juban Sabrina Ben Larbi Michèle Weiss‐Gayet Laurent Bultot Marc Foretz Dominique Desplanches Pascual Sanz Zizhao Zang Lin Yang Guillaume Vial Benoit Viollet Kei Sakamoto Anne Brunet Bénédicte Chazaud Rémi Mounier 《The EMBO journal》2017,36(13):1946-1962
Control of stem cell fate to either enter terminal differentiation versus returning to quiescence (self‐renewal) is crucial for tissue repair. Here, we showed that AMP‐activated protein kinase (AMPK), the master metabolic regulator of the cell, controls muscle stem cell (MuSC) self‐renewal. AMPKα1?/? MuSCs displayed a high self‐renewal rate, which impairs muscle regeneration. AMPKα1?/? MuSCs showed a Warburg‐like switch of their metabolism to higher glycolysis. We identified lactate dehydrogenase (LDH) as a new functional target of AMPKα1. LDH, which is a non‐limiting enzyme of glycolysis in differentiated cells, was tightly regulated in stem cells. In functional experiments, LDH overexpression phenocopied AMPKα1?/? phenotype, that is shifted MuSC metabolism toward glycolysis triggering their return to quiescence, while inhibition of LDH activity rescued AMPKα1?/? MuSC self‐renewal. Finally, providing specific nutrients (galactose/glucose) to MuSCs directly controlled their fate through the AMPKα1/LDH pathway, emphasizing the importance of metabolism in stem cell fate. 相似文献
259.
Coagulation factor VIIa (FVIIa) is a key protease initiating the coagulation cascade in the presence of its receptor, tissue factor (TF). FVIIa elicits several cellular responses, probably involving other receptors(s) than TF. This study investigates the implication of recombinant FVIIa on the apoptosis of K562 erythroleukemia cells. These cells undergo apoptosis when induced to differentiate towards the erythroid lineage by hemin. They do not express TF, but can be transfected to do so. FVIIa treatment significantly reduced the degree of hemin-induced apoptosis in K562 cells, but not in TF+ derived transfectants. Induction of apoptosis by hemin also elicited decrease in intracellular Ca2+ concentration ([Ca2+]i), but FVIIa restored this [Ca2+]i close to that of non-treated cells. These results suggest that FVIIa acts via a TF-independent pathway to counteract apoptosis by a mechanism involving its Gla domain and linked to the maintenance of Ca2+ homeostasis in K562 cells. 相似文献
260.
Built to bite? Differences in cranial morphology and bite performance between narrow‐ and broad‐headed European glass eels 下载免费PDF全文
Jens De Meyer Sam Van Wassenbergh Mathias Bouilliart Jelle Dhaene Dominique Adriaens 《Journal of morphology》2018,279(3):349-360
The presence of two phenotypes in a single species is a widespread phenomenon, also observed in European eel (Anguilla anguilla). This dimorphism has been related to dietary differences in the subadult elver and yellow eel stages, with broad‐heads generally feeding on harder and/or larger‐bodied prey items than narrow‐heads. Nevertheless, both broad‐ and narrow‐headed phenotypes can already be found among glass eels, the stage preceding the elver eel stage. As these glass eels are considered nonfeeding, we investigate here to what degree the observed variation in head width is reflected in variation in the musculoskeletal feeding system, as well as whether this reflects the same variation observed in the older, dimorphic yellow eels. Additionally, we investigate whether musculoskeletal differences between broad‐ and narrow‐headed glass eels have implications on their feeding performance and could thus impact prey preference when eels start feeding. Therefore, we compared the cranial musculoskeletal system of five broad‐ and narrow‐headed glass eels using 3D‐reconstructions and simulated the glass eel's bite force using the data of the muscle reconstructions. We found that the variation in the musculoskeletal system of glass eels indeed reflects that of the yellow eels. Broader heads were related to larger jaw muscles, responsible for mouth closure. Accordingly, broad‐heads could generate higher bite forces than narrow‐headed glass eels. In addition, broader heads were associated with higher coronoid processes and shorter hyomandibulae, beneficial for dealing with higher mechanical loadings and consequently, harder prey. We, thus, show that head width variation in glass eels is related to musculoskeletal differences which, in turn, can affect feeding performance. As such, differences in prey preference can already take place the moment the eels start feeding, potentially leading to the dimorphism observed in the elver and yellow eel stage. 相似文献