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排序方式: 共有188条查询结果,搜索用时 31 毫秒
21.
A new cembranolide, acerolide (1) together with the known compound pseudopterolide (2) were isolated from the 2-propanol extract of the soft coral Pseudopterogorgia acerosa. The structure of 1 was determined on the basis of detailed spectroscopic analysis. Compound 1 showed moderate in vitro cytotoxicity against a panel of 14 tumor cell lines. 相似文献
22.
Nguyen Van Bon Wang San-Lang Nguyen Thi Hanh Doan Chien Thang Tran Thi Ngoc Kuo Yao-Haur Nguyen Quang Vinh Nguyen Anh Dzung 《Research on Chemical Intermediates》2019,45(12):6061-6071
Research on Chemical Intermediates - Natural α-glucosidase inhibitors (aGIs) have been considered effective agents for type 2 diabetes management. In this study, Syzygium zeylanicum (L.)... 相似文献
23.
Airborne single-wall carbon nanotubes (SWCNTs) have a high tendency to agglomerate due to strong interparticle attractive
forces. The SWCNT agglomerates generally have complex morphologies with an intricate network of bundles of nanotubes and nanoropes,
which limits their usefulness in many applications. It is thus desirable to produce SWCNT aerosol particles that have well-defined,
unagglomerated fibrous morphologies. We present a method to generate unagglomerated, fibrous particles of SWCNT aerosols using
capillary electrospray of aqueous suspensions. The effects of the operating parameters of capillary electrospray such as strength
of buffer solution, capillary diameter, flow rate, and colloidal particle concentration on the size distributions of SWCNT
aerosols were investigated. Results showed that electrospray from a suspension of higher nanotube concentration produced a
bimodal distribution of SWCNT aerosols. Monodisperse SWCNT aerosols below 100 nm were mostly non-agglomerated single fibers,
while polydisperse aerosols larger than 100 nm had two distinct morphologies: a ribbon shape and the long, straight fiber.
Possible mechanisms are suggested to explain the formation of the different shapes, which could be used to produce SWCNT aerosols
with different morphologies. 相似文献
24.
Hauptvogel IM Bon V Grünker R Baburin IA Senkovska I Mueller U Kaskel S 《Dalton transactions (Cambridge, England : 2003)》2012,41(14):4172-4179
Five new coordination polymers, namely, [Zn(2)(H(2)O)(2)(BBC)](NO(3))(DEF)(6) (DUT-40), [Zn(3)(H(2)O)(3)(BBC)(2)] (DUT-41), [(C(2)H(5))(2)NH(2)][Zn(2)(BBC)(TDC)](DEF)(6)(H(2)O)(7) (DUT-42), [Zn(10)(BBC)(5)(BPDC)(2)(H(2)O)(10)](NO(3))(DEF)(28)(H(2)O)(8) (DUT-43), and [Co(2)(BBC)(NO(3))(DEF)(2)(H(2)O)](DEF)(6)(H(2)O) (DUT-44), where BBC--4,4',4'-(benzene-1,3,5-triyl-tris(benzene-4,1-diyl))tribenzoate, TDC--2,5-thiophenedicarboxylate, BPDC--4,4'-biphenyldicarboxylate, DEF--,N-diethylformamide, were obtained under solvothermal conditions and structurally characterized. It has been shown that compounds DUT-40, DUT-41 and DUT-44 exhibit 2D layered structures with large hexagonal channels. Utilization of additional angular dicarboxylic TDC linker led to the formation of the DUT-42 compound with the structure consisting of three interpenetrated 3D networks. Using the linear co-linker dicarboxylic BPDC, DUT-43 was obtained which forms a complicated 3D architecture arising from the polycatenation of triple-layered 2D building units and 2D single layer units. The pore accessibility of the synthesized compounds in the liquid phase was proved by the adsorption of dye molecules. 相似文献
25.
Deraeve C Guo Z Bon RS Blankenfeldt W DiLucrezia R Wolf A Menninger S Stigter EA Wetzel S Choidas A Alexandrov K Waldmann H Goody RS Wu YW 《Journal of the American Chemical Society》2012,134(17):7384-7391
Post-translational attachment of geranylgeranyl isoprenoids to Rab GTPases, the key organizers of intracellular vesicular transport, is essential for their function. Rab geranylgeranyl transferase (RabGGTase) is responsible for prenylation of Rab proteins. Recently, RabGGTase inhibitors have been proposed to be potential therapeutics for treatment of cancer and osteoporosis. However, the development of RabGGTase selective inhibitors is complicated by its structural and functional similarity to other protein prenyltransferases. Herein we report identification of the natural product psoromic acid (PA) that potently and selectively inhibits RabGGTase with an IC(50) of 1.3 μM. Structure-activity relationship analysis suggested a minimal structure involving the depsidone core with a 3-hydroxyl and 4-aldehyde motif for binding to RabGGTase. Analysis of the crystal structure of the RabGGTase:PA complex revealed that PA forms largely hydrophobic interactions with the isoprenoid binding site of RabGGTase and that it attaches covalently to the N-terminus of the α subunit. We found that in contrast to other protein prenyltransferases, RabGGTase is autoinhibited through N-terminal (α)His2 coordination with the catalytic zinc ion. Mutation of (α)His dramatically enhances the reaction rate, indicating that the activity of RabGGTase is likely regulated in vivo. The covalent binding of PA to the N-terminus of the RabGGTase α subunit seems to potentiate its interaction with the active site and explains the selectivity of PA for RabGGTase. Therefore, psoromic acid provides a new starting point for the development of selective RabGGTase inhibitors. 相似文献
26.
Bončina M Lah J Prislan I Vesnaver G 《Journal of the American Chemical Society》2012,134(23):9657-9663
Recent theoretical studies performed on the folding/unfolding mechanism of the model telomeric human DNA, 5'-AGGGTTAGGGTTAGGGTTAGGG-3' (Tel22), have indicated that in the presence of K(+) ions Tel22 folds into two hybrid G-quadruplex structures characterized by one double and two reversal TTA loops arranged in a different way. They predicted a new unfolding pathway from the initial mixture of hybrid G-quadruplexes via the corresponding intermediate triplex structures into the final, fully unfolded state. Significantly, no experimental evidence supporting the suggested pathway has been reported. In the current work, we performed a comprehensive global thermodynamic analysis of calorimetric (DSC, ITC) and spectroscopic (CD) data obtained on monitoring the folding/unfolding of Tel22 induced by changes of temperature and K(+) concentration. We show that unfolding of Tel22 may be described as a monomolecular equilibrium three-state process that involves thermodynamically distinguishable folded (F), intermediate (I), and unfolded (U) state. Considering that calorimetric methods cannot distinguish between energetically similar G-quadruplex or triplex conformations predicted by the theoretical model one can conclude that our results represent the first experimental support of the suggested unfolding/folding mechanism of Tel22. This conclusion is confirmed by the fact that the estimated number of K(+) ions released upon each unfolding step in our thermodynamic model agrees well with the corresponding values predicted by the theoretical model and that the observed changes in enthalpy, entropy, and heat capacity accompanying the F → I and I → U transitions can be reasonably explained only if the intermediate state I is considered to be a triplex structural conformation. 相似文献
27.
D. T. Souza A. S. R. Bispo E. P. S. Bon R. R. R. Coelho R. P. Nascimento 《Applied biochemistry and biotechnology》2012,166(6):1575-1585
In the present paper, endo-β-1,4-xylanase production by Aspergillus fumigatus was evaluated in solid-state fermentation using low-cost substrates such as sugarcane bagasse (SCB), brewer’s spent grain
(BSG), and wheat bran (WB). The partial characterization of the crude enzyme was also performed. In the experimental conditions,
the highest levels of endo-β-1,4-xylanase production by A. fumigatus FBSPE-05 occurred within 8 days incubation when using SCB/liquid medium at 1:2 ratio (219.5 U g−1) and 4 days incubation when using WB/liquid medium at 1:1 ratio (215.6 U g−1). Crude enzyme from this last condition was used to enzyme characterization, showing best enzyme activity at 60 °C and pH 6.0,
which suggests a thermophilic endoxylanase. The crude enzyme retained 73% of its activity after 1 h at 60 °C, and zymogram
has shown three bands of endo-β-1,4-xylanase activity, with different molecular masses. A. fumigatus FBSPE-05 was able to grow and produce good levels of endo-β-1,4-xylanase using agro-industrial by-products, making this strain
worthy for further investigation. To our knowledge, this is the first study reporting the use of SCB and/or BSG as sole substrates
for endoxylanase production by solid-state fermentation using A. fumigatus. 相似文献
28.
Tomographic diffractive microscopy with a wavefront sensor 总被引:1,自引:0,他引:1
Ruan Y Bon P Mudry E Maire G Chaumet PC Giovannini H Belkebir K Talneau A Wattellier B Monneret S Sentenac A 《Optics letters》2012,37(10):1631-1633
Tomographic diffractive microscopy is a recent imaging technique that reconstructs quantitatively the three-dimensional permittivity map of a sample with a resolution better than that of conventional wide-field microscopy. Its main drawbacks lie in the complexity of the setup and in the slowness of the image recording as both the amplitude and the phase of the field scattered by the sample need to be measured for hundreds of successive illumination angles. In this Letter, we show that, using a wavefront sensor, tomographic diffractive microscopy can be implemented easily on a conventional microscope. Moreover, the number of illuminations can be dramatically decreased if a constrained reconstruction algorithm is used to recover the sample map of permittivity. 相似文献
29.
Perišić-Janjić Nada U. Jevrić Lidija R. Bončić-Caričić Gordana A. Jovanović Bratislav Ž. 《平面色谱法杂志一现代薄层色谱法》2001,14(4):277-282
JPC – Journal of Planar Chromatography – Modern TLC - The chromatographic behavior of four groups of s-triazine derivatives (15 compounds) has been studied on aminoplast and cellulose... 相似文献
30.
Ferreira Viridiana S. Magalhães Denise B. Kling Sérgio H. Da Silva José G. Bon Elba P. S. 《Applied biochemistry and biotechnology》2000,84(1-9):255-265
Applied Biochemistry and Biotechnology - Phanerochaete chrysosporium lignin peroxidase (LiP) can degrade synthetic dyes such as heterocyclic, azo, and triphenylmethane on its activation by H2O2.... 相似文献