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1.
Contrary to an earlier report, lithiation of tris(trimethylsilyl)methane followed by carbonation does not yield the acid (Me3Si)3CCO2H, (I), if an alkali extraction step is included in the work up; the product is actually the acid (Me3Si)2CHCO2H, (II). The acid (I) can be obtained if the alkali extraction is omitted. Separate experiments have confirmed that (I) is rapidly converted into (II) by aqueous or methanolic base. 相似文献
2.
Rameesha Abid Shakira Ghazanfar Arshad Farid Samra Muhammad Sulaman Maryam Idrees Radwa Abdallnasser Amen Muhammad Muzammal Muhammad Khurram Shahzad Mohamed Omar Mohamed Alaa Ashraf Khaled Waqas Safir Ifra Ghori Abdelbaset Mohamed Elasbali Bandar Alharbi 《Molecules (Basel, Switzerland)》2022,27(13)
Plant bioactive compounds, particularly apigenin, have therapeutic potential and functional activities that aid in the prevention of infectious diseases in many mammalian bodies and promote tumor growth inhibition. Apigenin is a flavonoid with low toxicities and numerous bioactive properties due to which it has been considered as a traditional medicine for decades. Apigenin shows synergistic effects in combined treatment with sorafenib in the HepG2 human cell line (HCC) in less time and statistically reduces the viability of tumor cells, migration, gene expression and apoptosis. The combination of anti-cancerous drugs with apigenin has shown health promoting potential against various cancers. It can prevent cell mobility, maintain the cell cycle and stimulate the immune system. Apigenin also suppresses mTOR activity and raises the UVB-induced phagocytosis and reduces the cancerous cell proliferation and growth. It also has a high safety threshold, and active (anti-cancer) doses can be gained by consuming a vegetable and apigenin rich diet. Apigenin also boosted autophagosome formation, decreased cell proliferation and activated autophagy by preventing the activity of the PI3K pathway, specifically in HepG2 cells. This paper provides an updated overview of apigenin’s beneficial anti-inflammatory, antibacterial, antiviral, and anticancer effects, making it a step in the right direction for therapeutics. This study also critically analyzed the effect of apigenin on cancer cell signaling pathways including the PI3K/AKT/MTOR, JAK/STAT, NF-κB and ERK/MAPK pathways. 相似文献
3.
David E. Mery Amanda J. Compadre Paola E. Ordez Edward J. Selvik Vladimir Morocho Jorge Contreras Omar Malagn Darin E. Jones Philip J. Breen Michael J. Balick Flavio G. Gaudio Monica L. Guzman Cesar M. Compadre 《Molecules (Basel, Switzerland)》2022,27(9)
A method to identify anticancer compounds in plants was proposed based on the hypothesis that these compounds are primarily present in plants to provide them with an ecological advantage over neighboring plants and other competitors. According to this view, identifying plants that contain compounds that inhibit or interfere with the development of other plant species may facilitate the discovery of novel anticancer agents. The method was developed and tested using Magnolia grandiflora, Gynoxys verrucosa, Picradeniopsis oppositifolia, and Hedyosmum racemosum, which are plant species known to possess compounds with cytotoxic activities. Plant extracts were screened for growth inhibitory activity, and then a thin-layer chromatography bioautography assay was conducted. This located the major antileukemic compounds 1, 2, 4, and 5 in the extracts. Once the active compounds were located, they were extracted and purified, and their structures were determined. The growth inhibitory activity of the purified compounds showed a significant correlation with their antileukemic activity. The proposed approach is rapid, inexpensive, and can easily be implemented in areas of the world with high biodiversity but with less access to advanced facilities and biological assays. 相似文献
4.
Clifton K. Fagerquist Omar Sultan Michelle Q. Carter 《Journal of the American Society for Mass Spectrometry》2012,23(12):2102-2114
We previously reported the apparent formation of matrix adducts of 3,5-dimethoxy-4-hydroxy-cinnamic acid (sinapinic acid or SA) via covalent attachment to disulfide bond-containing proteins (HdeA, Hde, and YbgS) from bacterial cell lysates ionized by matrix-assisted laser desorption/ionization (MALDI) time-of-flight-time-of-flight tandem mass spectrometry (TOF-TOF-MS/MS) and post-source decay (PSD). We also reported the absence of adduct formation when using ??-cyano-4-hydroxycinnamic acid (CHCA) matrix. Further mass spectrometric analysis of disulfide-intact and disulfide-reduced over-expressed HdeA and HdeB proteins from lysates of gene-inserted E. coli plasmids suggests covalent attachment of SA occurs not at cysteine residues but at lysine residues. In this revised hypothesis, the attachment of SA is preceded by formation of a solid phase ammonium carboxylate salt between SA and accessible lysine residues of the protein during sample preparation under acidic conditions. Laser irradiation at 355?nm of the dried sample spot results in equilibrium retrogradation followed by nucleophilic attack by the amine group of lysine at the carbonyl group of SA and subsequent amide bond formation and loss of water. The absence of CHCA adducts suggests that the electron-withdrawing effect of the ??-cyano group of this matrix may inhibit salt formation and/or amide bond formation. This revised hypothesis is supported by dissociative loss of SA (?224?Da) and the amide-bound SA (?206?Da) from SA-adducted HdeA and HdeB ions by MS/MS (PSD). It is proposed that cleavage of the amide-bound SA from the lysine side-chain occurs via rearrangement involving a pentacyclic transition state followed by hydrogen abstraction/migration and loss of 3-(4-hydroxy-3,5-dimethoxyphenyl)prop-2-ynal (?206?Da). 相似文献
5.
Omar?Anza?HafsaEmail author Jean-Philippe?Mandallena 《Calculus of Variations and Partial Differential Equations》2003,18(4):433-449
We prove a new interchange theorem of infimum and integral. Its distinguishing feature is, on the one hand, to establish a general framework to deal with interchange problems for nonconvex integrands and nondecomposable sets, and, on the other hand, to link the theorems of Rockafellar and Hiai-Umegaki with the one of Bouchitté-Valadier. We give an application to relaxation of nonconvex geometric integrals of Calculus of Variations.Received: 20 March 2002, Accepted: 12 March 2003, Published online: 16 May 2003 相似文献
6.
Omar Ben-Ayed Charles E. Blair David E. Boyce Larry J. LeBlanc 《Annals of Operations Research》1992,34(1):219-254
The formulation of the highway network design problem (NDP) as a bilevel linear program (BLP) allows more realistic solutions taking into account the reaction of users to improvements made by the system. In this paper, a conceptual framework for the optimization of investments in inter-regional highway networks in developing countries is proposed. The model is applied to the Tunisian network using actual data. Considerable effort was expended to make the implementation as realistic as possible, taking into consideration travel times, operating costs, accident costs, improvement costs, conservation laws, and effects of intra-regional flows. A new formulation allowing the incorporation of any improvement cost functions, including non-convex and non-concave functions, is introduced. 相似文献
7.
Lianet Contreras Rodríguez Evaristo Jos Madarro-Cap
Carlos Miguel Legn-Prez
Omar Rojas Guillermo Sosa-Gmez 《Entropy (Basel, Switzerland)》2021,23(5)
Entropy makes it possible to measure the uncertainty about an information source from the distribution of its output symbols. It is known that the maximum Shannon’s entropy of a discrete source of information is reached when its symbols follow a Uniform distribution. In cryptography, these sources have great applications since they allow for the highest security standards to be reached. In this work, the most effective estimator is selected to estimate entropy in short samples of bytes and bits with maximum entropy. For this, 18 estimators were compared. Results concerning the comparisons published in the literature between these estimators are discussed. The most suitable estimator is determined experimentally, based on its bias, the mean square error short samples of bytes and bits. 相似文献
8.
Information entropy metrics have been applied to a wide range of problems that were abstracted as complex networks. This growing body of research is scattered in multiple disciplines, which makes it difficult to identify available metrics and understand the context in which they are applicable. In this work, a narrative literature review of information entropy metrics for complex networks is conducted following the PRISMA guidelines. Existing entropy metrics are classified according to three different criteria: whether the metric provides a property of the graph or a graph component (such as the nodes), the chosen probability distribution, and the types of complex networks to which the metrics are applicable. Consequently, this work identifies the areas in need for further development aiming to guide future research efforts. 相似文献
9.
10.
Noelio O. Dantas Valdeir A. Silva Omar. O. D. Neto Marcio L. F. Nascimento 《Brazilian Journal of Physics》2012,42(5-6):347-354
A glass matrix with nominal composition 50Li2O·45B2O3·5Al2O3 (mol%) was synthesized, and its physical properties were investigated by differential thermal analysis (DTA), X-ray diffraction (XRD), and atomic force microscopy (AFM). The glass transition temperature T g, the crystallization-onset temperature T x,, the crystallization peak temperatures T c1 and T c2, and the fusion peak temperatures T m1 and T m2 were determined from at least two glass matrix phases to be approximately 382, 457, 486, 574, 761, and 787?°C, respectively, at 5?°C/min heating rate. Heat treatments at 450?°C for an increasing sequence of time intervals allowed control over the amount of crystallization. Additional information on the crystallization kinetics for the LBA glass matrix was gathered from AFM images, DTA thermograms, and XRD diffractograms. The latter technique showed that LiBO2 (ICDD-16568) and Li3AlB2O6 (ICDD-51754) phases are formed in the glass?Cceramic system. Debye?CScherrer analysis of the XRD peaks revealed a competition between the evolutions of crystal phases during heat treatment. Activation energies for crystallization, obtained from theoretical models applied to the DTA data showed that the crystallization is heterogeneous. The AFM images demonstrated that this heterogeneous crystallization starts at the surface of the LBA glass matrix and identified crystal sizes in agreement with the results of the Debye?CScherrer analysis. Our study shows that thermal and structural characterization techniques can be combined with theoretical results drawn from well-tested models to offer a unified view of crystallization in a glass?Cceramics system. 相似文献