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991.
SNARE proteins mediate the fusion of lipid bilayers by the directed assembly of coiled-coil domains arising from apposing membranes. We have utilized inverted cone-shaped lipids, antagonists of the necessary membrane deformation during fusion to characterize the extent and range of SNARE assembly up to the moment of stalk formation between bilayers. The inverted cone-shaped lipid family of acyl-CoAs specifically inhibits the completion of fusion in an acyl-chain length-dependent manner. Removal of acyl-CoA from the membrane relieves the inhibition and initiates a burst of membrane fusion with rates exceeding any point in the control curves lacking acyl-CoA. This burst indicates the accumulation of semi-assembled fusion complexes. These preformed complexes are resistant to cleavage by botulinum toxin B and thus appear to have progressed beyond the "loosely zippered" state of docked synaptic vesicles. Surprisingly, application of the soluble domain of VAMP2, which blocks SNARE assembly by competing for binding on the available t-SNAREs, blocks recovery from the acyl-CoA inhibition. Thus, complexes formed in the presence of a lipidic antagonist to fusion are incompletely assembled, suggesting that the formation of tightly assembled SNARE pairs requires progression all the way through to membrane fusion. In this regard, physiologically docked exocytic vesicles may be anchored by a highly dynamic and potentially even reversible SNAREpin. 相似文献
992.
Woo CH Kim TH Choi JA Ryu HC Lee JE You HJ Bae YS Kim JH 《Biochemical and biophysical research communications》2006,351(4):972-978
Reactive oxygen species (ROS) are important regulatory molecules implicated in the signaling cascade triggered by tumor necrosis factor (TNF)alpha, although the events through which TNFalpha induces ROS generation are not well characterized. Here, we report that TNFalpha-induced ROS production was blocked by pretreatment with internalization inhibitor monodansyl cadaverine (MDC). Similarly, a transient expression of a GTP-binding and hydrolysis-defective dynamin mutant (dynamin(K44A)) that had been shown to be defective in internalization significantly attenuated the TNFalpha-induced intracellular ROS production. Importantly, the inhibition of receptor internalization suppressed TNFalpha signaling to mitogen-activated protein kinases (MAPKs) stimulation. Together, our results suggest that receptor internalization is somehow necessary for the TNFalpha-induced ROS generation and subsequent intracellular downstream signaling in non-phagocytes. 相似文献
993.
Three novel alkaline earth metal benzene-1,4-dioxylacetates M(L)H2O (M = Ca, Sr or Ba, L = benzene-1,4-dioxylacetate) with three-dimensional (3D) hybrid frameworks were reported. Both Ca(L)H2O (1) and Sr(L)H2O (2) crystallize in the monoclinic space group P21/c while Ba(L)H2O (3) in the monoclinic space group P21. As determined by X-ray single-crystal analysis, in these compounds each metal ion is coordinated by eight O atoms: four from different carboxylate groups, two from one carboxylate group, one from the ether oxygen and one from one water molecule. Each L2− ligand coordinates to five alkaline earth metal centers through one of its ether oxygen atoms and two carboxylate groups adopting novel μ3-η2:η2-bridging and μ2-η1:η1-bridging coordination modes to give rise to a 3D network. The luminescence analysis shows that complexes 1 and 2 exhibit fluorescence in the solid state at room temperature. 相似文献
994.
995.
Adamczyk M Chen YY Johnson DD Mattingly PG Moore JA Pan Y Reddy RE 《Bioorganic & medicinal chemistry letters》2006,16(5):1324-1328
Chemiluminescent acridinium-9-carboxamide probes containing 1, 3, 9, and 27 phenylboronic acids were prepared and their chemiluminescent properties evaluated. The relative chemiluminescent signal from the probes varied from 4 to 0.83 x 10(19)counts/mol across the series, while the apparent affinity of the probes for the diabetes marker glycated hemoglobin increased from 211 to 0.43 microM. The dose-dependent modulation of the chemiluminescent intensity of the probes upon binding was used to demonstrate a homogeneous assay for glycated hemoglobin. 相似文献
996.
997.
A series of pyrazole-bridged heterometallic 3d-4f complexes, [CuDy(ipdc)2(H2O)4] · (2H2O)(H3O+) (1) and [CuLn(pdc)(ipdc)(H2O)4] · H3O+ (Ln = Ho (2), Er (3), Yb (4); H3ipdc = 4-iodo-3,5-pyrazoledicarboxylic acid; H3pdc = 3,5-pyrazoledicarboxylic acid), {[Cu3Ln4(ipdc)6(H2O)16] · xH2O}n (Ln = Sm (5), x = 8.5; Ln = Eu (6), x = 7; Ln = Gd (7), Tb (8), x = 9), have been synthesized and structurally characterized. Ligand H3ipdc was in situ obtained by iodination of ligand H3pdc. Complexes 1-4 are pyrazole-bridged heterometallic dinuclear complexes, and 2-4 are isostructural. Complexes 5-8 are isostructural and comprised of an unusual infinite one-dimensional tape-like chain based on pyrazole-bridged heterometallic dinuclear units. The magnetic properties of compounds 1-4, 7 and 8 have been investigated through the magnetic measurement over the temperature range of 1.8-300 K. 相似文献
998.
A facile synthetic procedure has been used to prepare one five-coordinate and four six-coordinate copper(II) complexes of 4′-chloro-2,2′:6′,2″-terpyridine (tpyCl) ligand with different counterions (, , , , and ) in high yields. They are formulated as [Cu(tpyCl-κ3N,N′,N′′)(SO4-κO)(H2O-κO)] · 2H2O (1), trans-[Cu(tpyCl-κ3N,N′,N″)(NO3-κO)2(H2O-κO)] (2), [Cu(tpyCl-κ3N,N′,N″)2](BF4)2 (3), [Cu(tpyCl-κ3N,N′,N″)2](PF6)2 (4) and [Cu(tpyCl-κ3N,N′,N″)2](ClO4)2 (5) and versatile interactions in supramolecular level including coordinative bonding, O-H?O, O-H?Cl, C-H?F, and C-H?Cl hydrogen bonding, π-π stacking play essential roles in forming different frameworks of 1-5. It is concluded that the difference of coordination abilities of the counterions used and the experimental conditions codominate the resulting complexes with 1:1 or 1:2 ratio of metal and ligand. 相似文献
999.
Two new ruthenium (II) complexes containing coupled di(2-pyridyl) and 1,3-dithiole units, cis-[Ru(Medpydt)2(NCS)2] (2, Medpydt = dimethyl 2-(di(2-pyridyl)methylene)-1,3-dithiole-4,5-dicarboxylate) and cis-[Ru(H2dpydt)2(NCS)2] (3, H2dpydt = 2-(di(2-pyridyl)methylene)-1,3-dithiole-4,5-dicarboxylate), have been synthesized and characterized. The structure of complex 2 has been determined by X-ray crystallography. There exist intermolecular H-bonding interactions between carbomethoxy groups on neighboring pyridine rings giving rise to 2D H-bonded arrays. The metal-to-ligand charge-transfer (MLCT) absorptions were observed around 480 nm. Redox properties of ruthenium complexes have been investigated by cyclic voltammetry. Solar cells involving thin films of anatase TiO2 impregnated with cis-[Ru(H2dpydt)2(NCS)2] were prepared, and the photovoltaic performance was preliminarily investigated. 相似文献
1000.
Shi-Jie You Nan-Qi Ren Qing-Liang Zhao Patrick D. Kiely Jing-Yuan Wang Feng-Lin Yang Lei Fu Luo Peng 《Biosensors & bioelectronics》2009,24(12):3698-3701
To reduce the amount of phosphate buffer currently used in Microbial Fuel Cell's (MFC's), we investigated the role of biological nitrification at the cathode in the absence of phosphate buffer. The addition of a nitrifying mixed consortia (NMC) to the cathode compartment and increasing ammonium concentration in the catholyte resulted in an increase of cell voltage from 0.3 V to 0.567 V (external resistance of 100 Ω) and a decrease of catholyte pH from 8.8 to 7.05. A large fraction of ammonium was oxidized to nitrite, as indicated by an increase of nitrate-nitrogen (NO3−–N). An MFC inoculated with an NMC and supplied with 94.2 mgN/l ammonium to the catholyte could generate a maximum power of 2.1 ± 0.14 mW (10.94 ± 0.73 W/m3). This compared favorably to an MFC supplied with either buffered or non-buffered solution. The buffer-free NMC inoculated cathodic chamber showed the smallest polarization resistance, suggesting that nitrification resulted in improved cathode performance. The improved performances of the phosphate buffer-free cathode and cell are positively related to biological nitrification, in which we suggest additional protons produced from ammonium oxidation facilitated electrochemical reduction of oxygen at cathode. 相似文献