20 research outputs found

    Asymmetric Hydrogenation in Water by a Rhodium Complex of Sulfonated 2,2'-Bis(diphenylphosphino)-1,1'-binaphthyl (binap)

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    The synthesis of sulfonated 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl (binap) is reported; a rhodium complex of this ligand is the first to perform asymmetric hydrogenation in neat water with optical yields as high as those obtained in nonaqueous solvent

    An Epstein-Barr virus–encoded microRNA targets PUMA to promote host cell survival

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    Epstein-Barr virus (EBV) is a herpesvirus associated with nasopharyngeal carcinoma (NPC), gastric carcinoma (GC), and other malignancies. EBV is the first human virus found to express microRNAs (miRNAs), the functions of which remain largely unknown. We report on the regulation of a cellular protein named p53 up-regulated modulator of apoptosis (PUMA) by an EBV miRNA known as miR-BART5, which is abundantly expressed in NPC and EBV-GC cells. Modulation of PUMA expression by miR-BART5 and anti–miR-BART5 oligonucleotide was demonstrated in EBV-positive cells. In addition, PUMA was found to be significantly underexpressed in ∼60% of human NPC tissues. Although expression of miR-BART5 rendered NPC and EBV-GC cells less sensitive to proapoptotic agents, apoptosis can be triggered by depleting miR-BART5 or inducing the expression of PUMA. Collectively, our findings suggest that EBV encodes an miRNA to facilitate the establishment of latent infection by promoting host cell survival

    Immunoregulatory Protein Profiles of Necrotizing Enterocolitis versus Spontaneous Intestinal Perforation in Preterm Infants

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    Necrotizing enterocolitis (NEC) and spontaneous intestinal perforation (SIP) are the most common acute surgical emergencies associated with high morbidity and mortality in preterm infants. We aimed to compare the profiles of immunoregulatory proteins and identify novel mediators in plasma of NEC and SIP infants. We also investigated the expression of target genes in resected intestinal tissues and an enterocyte cell line. Using Cytokine Antibody Array assay, we reported the first comparative profiles of immunoregulatory proteins in plasma of NEC and SIP infants, and showed that dysregulated proteins belonged to functionally diversified categories, including pro- and anti-inflammation, angiogenesis, cell growth, wound healing, anti-apoptosis, cell adhesion and extracellular matrix reorganization. Validation by ELISA confirmed significantly higher concentrations of interleukin (IL)-6, angiopoietin (Ang)-2, soluble type II interleukin-1 receptor (sIL-1RII), and soluble urokinase-type plasminogen activator receptor (suPAR) in NEC infants compared with gestational age-matched control, and a lower level of an epidermal growth factor receptor, secreted form of receptor tyrosine-protein kinase ErbB3 (sErbB3), compared with SIP infants. mRNA expressions of IL1-RII and uPAR were up-regulated in resected bowel tissues from NEC infants, indicating that immunoregulation also occurred at the cellular level. In FHs-74 Int cells, Ang-2, IL1-RII and uPAR mRNA expressions were significantly induced by the combined treatment with lipopolysaccharide (LPS) and platelet activating factor (PAF). Our study provided plasmatic signatures of immunoregulatory proteins in NEC and SIP infants, and demonstrated involvement of multiple functional pathways. The magnitude of changes in these proteins was significantly more extensive in NEC infants, reflecting the different nature of injury and/or severity of inflammation. We speculate that dysregulation of IL-6, Ang-2, IL-1RII and uPAR occurred at both systemic and cellular levels, and probably mediated via LPS and endogeneous PAF signals. Such exaggerated immunologic responses may account for the high morbidity and mortality in NEC compared with SIP patients

    The Design and Synthesis of a True, Heterogeneous, Asymmetric Catalyst

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    This work describes the design and synthesis of a true, heterogeneous, asymmetric catalyst. The catalyst consists of a thin film that resides on a high-surface- area hydrophilic solid and is composed of a chiral, hydrophilic organometallic complex dissolved in ethylene glycol. Reactions of prochiral organic reactants take place predominantly at the ethylene glycol-bulk organic interface. The synthesis of this new heterogeneous catalyst is accomplished in a series of designed steps. A novel, water-soluble, tetrasulfonated 2,2'-bis (diphenylphosphino)-1,1'-binaphthyl (BINAP-4S0_3Na) is synthesized by direct sulfonation of 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (BINAP). The rhodium (I) complex of BINAP-4SO_3Na is prepared and is shown to be the first homogeneous catalyst to perform asymmetric reductions of prochiral 2-acetamidoacrylic acids in neat water with enantioselectivities as high as those obtained in non-aqueous solvents. The ruthenium (II) complex, [Ru(BINAP-4SO_3Na)(benzene)Cl]Cl is also synthesized and exhibits a broader substrate specificity as well as higher enantioselectivities for the homogeneous asymmetric reduction of prochiral 2-acylamino acid precursors in water. Aquation of the ruthenium-chloro bond in water is found to be detrimental to the enantioselectivity with some substrates. Replacement of water by ethylene glycol results in the same high e.e's as those found in neat methanol. The ruthenium complex is impregnated onto a controlled pore-size glass CPG-240 by the incipient wetness technique. Anhydrous ethylene glycol is used as the immobilizing agent in this heterogeneous catalyst, and a non-polar 1:1 mixture of chloroform and cyclohexane is employed as the organic phase. Asymmetric reduction of 2-(6'-methoxy-2'-naphthyl)acrylic acid to the non-steroidal anti-inflammatory agent, naproxen, is accomplished with this heterogeneous catalyst at a third of the rate observed in homogeneous solution with an e.e. of 96% at a reaction temperature of 3°C and 1,400 psig of hydrogen. No leaching of the ruthenium complex into the bulk organic phase is found at a detection limit of 32 ppb. Recycling of the catalyst is possible without any loss in enantioselectivity. Long-term stability of this new heterogeneous catalyst is proven by a self-assembly test. That is, under the reaction conditions, the individual components of the present catalytic system self-assemble into the supported-catalyst configuration. The strategies outlined here for the design and synthesis of this new heterogeneous catalyst are general, and can hopefully be applied to the development of other heterogeneous, asymmetric catalysts. </p

    Syntheses and photochemistry of monomeric platinum (II) complexes

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    published_or_final_versionChemistryMasterMaster of Philosoph

    Reactions of meta-xylene on zeolites with intersecting medium and large pores I. Basic studies

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    The reactions of m-xylene are conducted over all known zeolites with intersecting medium and large pores (MCM-22, NU-87, CIT-1, SSZ-33, SSZ-26) and the results compared to those from large (SSZ-24, ZSM-12, zeolite beta, zeolite L) and medium (ZSM-5, EU-1) pore zeolites. Each of the materials MCM-22, NU-87 and CIT-1/SSZ-33/SSZ-26 reveals a unique reaction behavior in terms of the p-xyleneo-xylene and isomerization/disproportionation ratios, the distribution of formed trimethylbenzenes and the rate of deactivation. The reaction activities and selectivities of MCM-22 and CIT-1/SSZ-33/SSZ-26 are somewhat like medium and large pore zeolites, respectively, as is expected from their crystal structures. NU-87 displays a lower p-xyleneo-xylene ratio and a higher turnover frequency than predicted from the crystal structure
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