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991.
A structure revision for the recently isolated fungal meroterpenoids, cytosporolides A-C, is suggested based on biosynthetic speculation and reinterpretation of existing spectroscopic data. The structure revision is supported by a biomimetic synthetic study, featuring a [4 + 2] cycloaddition reaction between a presumed o-quinone methide intermediate and β-caryophyllene. 相似文献
992.
Looking-glass synergistic pharmacological chaperones: DGJ and L-DGJ from the enantiomers of tagatose
Jenkinson SF Fleet GW Nash RJ Koike Y Adachi I Yoshihara A Morimoto K Izumori K Kato A 《Organic letters》2011,13(15):4064-4067
The enantiomers of tagatose are converted to L-DGJ [a noncompetitive inhibitor of human lysosome α-galactosidase A (α-Gal A), K(i) 38.5 μM] and DGJ [a competitive inhibitor of α-Gal A, K(i) 15.1 nM] in 66% yield. L-DGJ and DGJ provide the first examples of pharmacological chaperones that (a) are enantiomeric iminosugars and (b) have synergistic activity with implications for the treatment of lysosomal storage disorders and other protein deficiencies. 相似文献
993.
Bai R Nguyen TL Burnett JC Atasoylu O Munro MH Pettit GR Smith AB Gussio R Hamel E 《Journal of chemical information and modeling》2011,51(6):1393-1404
Compounds that modulate microtubule dynamics include highly effective anticancer drugs, leading to continuing efforts to identify new agents and improve the activity of established ones. Here, we demonstrate that [(3)H]-labeled halichondrin B (HB), a complex, sponge-derived natural product, is bound to and dissociated from tubulin rapidly at one binding site per αβ-heterodimer, with an apparent K(d) of 0.31 μM. We found no HB-induced aggregation of tubulin by high-performance liquid chromatography, even following column equilibration with HB. Binding of [(3)H]HB was competitively inhibited by a newly approved clinical agent, the truncated HB analogue eribulin (apparent K(i), 0.80 μM) and noncompetitively by dolastatin 10 and vincristine (apparent K(i)'s, 0.35 and 5.4 μM, respectively). Our earlier studies demonstrated that HB inhibits nucleotide exchange on β-tubulin, and this, together with the results presented here, indicated the HB site is located on β-tubulin. Using molecular dynamics simulations, we determined complementary conformations of HB and β-tubulin that delineated in atomic detail binding interactions of HB with only β-tubulin, with no involvement of the α-subunit in the binding interaction. Moreover, the HB model served as a template for an eribulin binding model that furthered our understanding of the properties of eribulin as a drug. Overall, these results established a mechanistic basis for the antimitotic activity of the halichondrin class of compounds. 相似文献
994.
Chlipala GE Krunic A Mo S Sturdy M Orjala J 《Journal of chemical information and modeling》2011,51(1):171-180
A software package, termed "CYANOS", has been developed to facilitate the data management and mining for natural product drug discovery efforts. This system allows for the management of data associated with field collections, culture conditions, harvests, extractions, chemical separations, and biological evaluation. This software utilizes a MySQL database for data storage, which allows for reporting and data mining via third party tools. In addition, a Web-based interface was constructed to allow for multiuser access from a variety of desktop platforms. The code for this system is freely available and has been released under the Illinois Open Source license. 相似文献
995.
Geis-Asteggiante L Lehotay SJ Fortis LL Paoli G Wijey C Heinzen H 《Analytical and bioanalytical chemistry》2011,401(8):2617-2630
Microcystins (MCs) are the most common cyanotoxins found worldwide in freshwater, brackish, and marine environments. The rapid
and accurate analysis of MCs and nodularin (Nod-R) in fish tissue is important for determining occurrence, following trends,
and monitoring exposure for risk assessment and other purposes. The aim of this study was to develop a streamlined and reliable
sample preparation method for eight MCs (MC-RR, MC-YR, MC-LR, MC-WR, MC-LA, MC-LY, MC-LW, and MC-LF) and Nod-R in fish, and
conduct a validation of the new method using liquid chromatography–tandem mass spectrometry (LC-MS/MS) for analysis and compare
the results with a commercial enzyme-linked immunosorbent assay (ELISA) kit. Different sample preparation methods were compared,
and a simple extraction protocol with acidified acetonitrile/water (3:1) followed by hexane partitioning cleanup was found
to be most effective. Thorough validation of the final method was conducted, and 90–115% recoveries were achieved for all
analytes except for MC-RR, which gave 130% average recovery (isotopically labeled internal standards were unavailable to correct
for possible biases). The use of electrospray ionization in the negative mode gave few interferences and minimal matrix effects
in the LC-MS/MS analysis overall. Precision was typically 10–20% RSD among multiple days in experiments, detection limits
were <10 ng/g in the fish tissue (catfish, basa, and swai filets), and no false-positives or false-negatives occurred in blind
analyses of many spiked samples. The ELISA was unable to distinguish between MCs but was found to correctly assess the presence
or absence of MCs and Nod-R in the blind-fortified fish tissues. The capability of these approaches to measure covalently
bound MCs was not assessed. 相似文献
996.
Chien CC Zhang G Hwu Y Liu P Yue W Sun J Li Y Xu H Xue H Xu LX Wang CH Chen N Lu CH Lee TK Yang YC Lu YT Ching YT Shih TF Yang PC Je JH Margaritondo G 《Analytical and bioanalytical chemistry》2011,401(3):827-835
Refractive-index (phase-contrast) radiology was able to detect lung tumors less than 1 mm in live mice. Significant micromorphology differences were observed in the microradiographs between normal, inflamed, and lung cancer tissues. This was made possible by the high phase contrast and by the fast image taking that reduces the motion blur. The detection of cancer and inflammation areas by phase contrast microradiology and microtomography was validated by bioluminescence and histopathological analysis. The smallest tumor detected is less than 1 mm(3) with accuracy better than 1 × 10(-3) mm(3). This level of performance is currently suitable for animal studies, while further developments are required for clinical application. 相似文献
997.
998.
We introduce the WeightedGrammar constraint and propose propagation algorithms based on the CYK parser and the Earley parser. We show that the traces of these algorithms can be encoded as a weighted negation normal form (WNNF), a generalization of NNF that allows nodes to carry weights. Based on this connection, we prove the correctness and complexity of these algorithms. Specifically, these algorithms enforce domain consistency on the WeightedGrammar constraint in time O(n 3). Further, we propose that the WNNF constraint can be decomposed into a set of primitive arithmetic constraint without hindering propagation. 相似文献
999.
George A. Anastassiou 《Mathematical and Computer Modelling》2011,53(5-6):1111-1132
Here we study the univariate quantitative approximation of real and complex valued continuous functions on a compact interval or all the real line by quasi-interpolation hyperbolic tangent neural network operators. This approximation is derived by establishing Jackson type inequalities involving the modulus of continuity of the engaged function or its high order derivative. Our operators are defined by using a density function induced by the hyperbolic tangent function. The approximations are pointwise and with respect to the uniform norm. The related feed-forward neural network is with one hidden layer. 相似文献
1000.
We study the forcing operators on MTL‐algebras, an algebraic notion inspired by the Kripke semantics of the monoidal t ‐norm based logic (MTL). At logical level, they provide the notion of the forcing value of an MTL‐formula. We characterize the forcing operators in terms of some MTL‐algebras morphisms. From this result we derive the equality of the forcing value and the truth value of an MTL‐formula (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献