排序方式: 共有59条查询结果,搜索用时 0 毫秒
31.
(+)-4-Demethoxy-1,4-dimethyldaunomycinone 1 was synthesized using a convergent approach. Here, the key tetracyclic compound 10 was assembled by way of a Diels-Alder reaction using the sugar-based diene 8 and the quinizarin-related dienophile 7. 相似文献
32.
Ramsey ME Hackett KT Kotha C Dillard JP 《Applied and environmental microbiology》2012,78(9):3068-3078
We have created new complementation constructs for use in Neisseria gonorrhoeae and Neisseria meningitidis. The constructs contain regions of homology with the chromosome and direct the insertion of a gene of interest into the intergenic region between the genes iga and trpB. In order to increase the available options for gene expression in Neisseria, we designed the constructs to contain one of three different promoters. One of the constructs contains the isopropyl-β-d-thiogalactopyranoside-inducible lac promoter, which has been widely used in Neisseria. We also designed a construct that contains the strong, constitutive promoter from the gonococcal opaB gene. The third construct contains a tetracycline-inducible promoter, a novel use of this promoter in Neisseria. We demonstrate that anhydrotetracycline can be used to induce gene expression in the pathogenic Neisseria at very low concentrations and without negatively affecting the growth of the organisms. We use these constructs to complement an arginine auxotrophy in N. gonorrhoeae as well as to express a translational fusion of alkaline phosphatase with TraW. TraW is a component of the gonococcal type IV secretion system, and we demonstrate that TraW localizes to the periplasm. 相似文献
33.
Meghan E. Ramsey Kathleen T. Hackett Tobias Bender Chaitra Kotha Chris van der Does Joseph P. Dillard 《Journal of bacteriology》2014,196(16):2954-2968
Neisseria gonorrhoeae uses a type IV secretion system (T4SS) to secrete chromosomal DNA into the medium, and this DNA is effective in transforming other gonococci via natural transformation. In addition, the T4SS is important in the initial stages of biofilm development and mediates intracellular iron uptake in the absence of TonB. To better understand the mechanism of type IV secretion in N. gonorrhoeae, we examined the expression levels and localization of two predicted T4SS outer membrane proteins, TraK and TraB, in the wild-type strain as well as in overexpression strains and in a strain lacking all of the T4SS proteins. Despite very low sequence similarity to known homologues, TraB (VirB10 homolog) and TraK (VirB9 homolog) localized similarly to related proteins in other systems. Additionally, we found that TraV (a VirB7 homolog) interacts with TraK, as in other T4SSs. However, unlike in other systems, neither TraK nor TraB required the presence of other T4SS components for proper localization. Unlike other gonococcal T4SS proteins we have investigated, protein levels of the outer membrane proteins TraK and TraB were extremely low in wild-type cells and were undetectable by Western blotting unless overexpressed or tagged with a FLAG3 triple-epitope tag. Localization of TraK-FLAG3 in otherwise wild-type cells using immunogold electron microscopy of thin sections revealed a single gold particle on some cells. These results suggest that the gonococcal T4SS may be present in single copy per cell and that small amounts of T4SS proteins TraK and TraB are sufficient for DNA secretion. 相似文献
34.
35.
Tetralin-based constrained alpha-amino acid derivatives were prepared via [4 + 2]-cycloaddition reaction as a key step. Here sultine is used as a latent diene and 2-acetamidoacrylate serves as a dienophile component. 相似文献
36.
37.
Shariq I. Sherwani Sheila Pabon Rishi B. Patel Muzzammil M. Sayyid Thomas Hagele Sainath R. Kotha Ulysses J. Magalang Krishna R. Maddipati Narasimham L. Parinandi 《Cell biochemistry and biophysics》2013,67(2):317-329
Mercury, especially methylmercury (MeHg), is implicated in the etiology of cardiovascular diseases. Earlier, we have reported that MeHg induces phospholipase D (PLD) activation through oxidative stress and thiol-redox alteration. Hence, we investigated the mechanism of the MeHg-induced PLD activation through the upstream regulation by phospholipase A2 (PLA2) and lipid oxygenases such as cyclooxygenase (COX) and lipoxygenase (LOX) in the bovine pulmonary artery endothelial cells (BPAECs). Our results showed that MeHg significantly activated both PLA2 (release of [3H]arachidonic acid, AA) and PLD (formation of [32P]phosphatidylbutanol) in BPAECs in dose- (0–10 μM) and time-dependent (0–60 min) fashion. The cPLA2-specific inhibitor, arachidonyl trifluoromethyl ketone (AACOCF3), significantly attenuated the MeHg-induced [3H]AA release in ECs. MeHg-induced PLD activation was also inhibited by AACOCF3 and the COX- and LOX-specific inhibitors. MeHg also induced the formation of COX- and LOX-catalyzed eicosanoids in ECs. MeHg-induced cytotoxicity (based on lactate dehydrogenase release) was protected by PLA2-, COX-, and LOX-specific inhibitors and 1-butanol, the PLD-generated PA quencher. For the first time, our studies showed that MeHg activated PLD in vascular ECs through the upstream action of cPLA2 and the COX- and LOX-generated eicosanoids. These results offered insights into the mechanism(s) of the MeHg-mediated vascular endothelial cell lipid signaling as an underlying cause of mercury-induced cardiovascular diseases. 相似文献
38.
Kotha S Sreenivasachary N Mohanraja K Durani S 《Bioorganic & medicinal chemistry letters》2001,11(11):1421-1423
Ring-closing metathesis (RCM) with alpha,alpha-diallylglycyl peptides is shown to furnish alpha,alpha-cyclopentenylglycyl peptides as conformationally restrained analogues in the form of post-translational type peptide modification suitable for both peptidomimetic and combinatorial chemistry applications. 相似文献
39.
Michael J. Herr Celia M. Longhurst Benjamin Baker Ramin Homayouni Henry E. Speich Jayaprakash Kotha Lisa K. Jennings 《Biochemical and biophysical research communications》2014
Non-Hodgkin Lymphoma (NHL) is a type of hematological malignancy that affects two percent of the overall population in the United States. Tetraspanin CD9 is a cell surface protein that has been thoroughly demonstrated to be a molecular facilitator of cellular phenotype. CD9 expression varies in two human lymphoma cell lines, Raji and BJAB. In this report, we investigated the functional relationship between CD9 and cell proliferation regulated by histone deacetylase (HDAC) activity in these two cell lines. Introduction of CD9 expression in Raji cells resulted in significantly increased cell proliferation and HDAC activity compared to Mock transfected Raji cells. The increase in CD9–Raji cell proliferation was significantly inhibited by HDAC inhibitor (HDACi) treatment. Pretreatment of BJAB cells with HDAC inhibitors resulted in a significant decrease in endogenous CD9 mRNA and cell surface expression. BJAB cells also displayed decreased cell proliferation after HDACi treatment. These results suggest a significant relationship between CD9 expression and cell proliferation in human lymphoma cells that may be modulated by HDAC activity. 相似文献
40.