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排序方式: 共有652条查询结果,搜索用时 15 毫秒
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Mariia Savchuk Lucas Bocquin Muriel Albalat Marion Jean Nicolas Vanthuyne Paola Nava Stphane Humbel Damien Hrault Herv Clavier 《Chirality》2022,34(1):13-26
From achiral imidazolinium salts, chiral transition metal complexes containing an N-heterocyclic carbene (NHC) ligand were prepared (metal = palladium, copper, silver, gold, rhodium). Axial chirality in these complexes results from the formation of the metal-carbene bond leading to the restriction of rotation of dissymmetric N-aryl substituents about the C–N bond. When these complexes exhibited a sufficient configurational stability, a resolution by chiral high-performance liquid chromatography (HPLC) on preparative scale enabled isolation of enantiomers with excellent enantiopurities (>99% ee) and good yields. A study of the enantiomerization barriers revealed the effect of the backbone nature as well as the type of transition metal on its values. Nevertheless, the evaluation of palladium-based complexes in asymmetric intramolecular α-arylation of amides demonstrated that the ability to induce an enantioselectivity cannot be correlated to the configurational stability of the precatalysts. 相似文献
64.
Marc Kschonsak Christian H. Haering 《BioEssays : news and reviews in molecular, cellular and developmental biology》2015,37(7):755-766
How eukaryotic genomes are packaged into compact cylindrical chromosomes in preparation for cell divisions has remained one of the major unsolved questions of cell biology. Novel approaches to study the topology of DNA helices inside the nuclei of intact cells, paired with computational modeling and precise biomechanical measurements of isolated chromosomes, have advanced our understanding of mitotic chromosome architecture. In this Review Essay, we discuss – in light of these recent insights – the role of chromatin architecture and the functions and possible mechanisms of SMC protein complexes and other molecular machines in the formation of mitotic chromosomes. Based on the information available, we propose a stepwise model of mitotic chromosome condensation that envisions the sequential generation of intra‐chromosomal linkages by condensin complexes in the context of cohesin‐mediated inter‐chromosomal linkages, assisted by topoisomerase II. The described scenario results in rod‐shaped metaphase chromosomes ready for their segregation to the cell poles. 相似文献
65.
Symbiodinium transcriptome and global responses of cells to immediate changes in light intensity when grown under autotrophic or mixotrophic conditions
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The 3-aryl-2-cyanoacrylamide scaffold was designed as core pharmacophore for inhibitors of the Dengue and West Nile virus serine proteases (NS2B-NS3). A total of 86 analogs was prepared to study the structure–activity relationships in detail. Thereby, it turned out that the electron density of the aryl moiety and the central double bond have a crucial influence on the activity of the compounds, whereas the influence of substituents of the amide residue is less relevant. The para-hydroxy substituted analog was found to be the most potent inhibitor in this series with a Ki-value of 35.7 μM at the Dengue and 44.6 μM at the West Nile virus protease. The aprotinin competition assay demonstrates a direct interaction of the inhibitor molecule with active centre of the Dengue virus protease. The target selectivity was studied in a counterscreen with thrombin and found to be 2.8:1 in favor of DEN protease and 2.3:1 in favor of WNV protease, respectively. 相似文献
67.
Kim JY Cho SW Song WC Lee MJ Cai J Ohk SH Song HK Degan A Jung HS 《Differentiation; research in biological diversity》2005,73(5):240-248
Chick feather buds develop sequentially in a hexagonal array. Each feather bud develops with anterior posterior polarity, which is thought to develop in response to signals derived from specialized regions of mesenchymal condensation and epithelial thickening. These developmental processes are performed by cellular mechanisms, such as cell proliferation and migration, which occur during chick feather bud development. In order to understand the mechanisms regulating the formation of mesenchymal condensation and their role in feather bud development, we explanted chick dorsal skin at stage HH29+ with cytochalasin D, which inhibits cytoskeletal formation. We show that the aggregation of mesenchymal cells can be prevented by cytochalasin D treatment in a concentration-dependent manner. Subsequently, cytochalasin D disrupts the spacing pattern and inhibits feather bud axis formation as well. In addition, expression patterns of Bmp-4 and Msx-2, key molecules for early feather bud development, were disturbed by cytochalasin D treatment. Our results fully indicate that both the cytoskeletal structure and cell activity via gene regulation are of fundamental importance in mesenchymal condensation leading to proper morphogenesis of feather bud and spacing pattern formation. 相似文献
68.
Recently, we found that intracellular washout of cGMP induces gap junction uncoupling and proposed a link between gap junction
uncoupling and stimulation of apoptotic reactions in GFSHR-17 granulosa cells. In the present report we show that an inhibitor
of guanylyl cyclase, ODQ, reduces gap junction coupling and promotes apoptotic reactions such as chromatin condensation and
DNA strand breaks. To analyze whether gap junction uncoupling and induction of apoptotic reactions are related, the cells
were treated with heptanol and 18β-GA, two known gap junction uncouplers. Gap junction coupling of GFSHR-17 cells could be
restored if the incubation time with the gap junction uncouplers was less than 10 min. A prolonged incubation time irreversibly
suppressed gap junction coupling and caused chromatin condensation as well as DNA degradation. The promotion of apoptotic
reactions by heptanol or 18β-GA was not observed in cells with low gap junction coupling like HeLa cells, indicating that
the observed genotoxic reactions are not caused by unspecific effects of gap junction uncouplers. Additionally, it was observed
that heptanol or 18β-GA did not induce a sustained rise of [Ca2+]i. The effects of gap junction uncouplers could not be suppressed by the presence of 8-Br-cGMP. It is discussed that irreversible
gap junction uncoupling can be mediated by cGMP-dependent as well as cGMP-independent pathways and in turn could lead to stimulation
of apoptotic reactions in granulosa cells. 相似文献
69.
A novel strategy to prepare negatively charged and small DNA-containing liposomes after condensation of plasmid DNA by a cationic
lipid in deoxycholate micelle environment is described. The average diameter of resulting complexes was 62±8 nm. DNA-containing
liposomes were then prepared by dialysis. The shape of the resulting liposomes was spherical. The average diameter and the
surface charge of the liposomes were 86±6 nm and −24±3 mV, respectively. The plasmid DNA inside liposomes remained in a supercoiled
form after incubation with DNase. 相似文献
70.