http://hdl.handle.net/10397/9 Research materials by staff and student in this subject area. Search the Channel search http://repository.lib.polyu.edu.hk/jspui/simple-search http://hdl.handle.net/10397/5668 Title: Transition metal-catalyzed cyanation and isocyanation of aryl halides and sulfonates<br/><br/>Authors: Yeung, Pui-yee<br/><br/>Abstract: The mildest cyanation has been developed for aryl halides and sulfonates with environmental friendly cyanating source: K₄[Fe(CN)₆]3H₂O. In the presence of highly effective Pd/CMPhos catalyst, cyanation of aryl chlorides proceeds at 70 °C in general, which is the mildest reaction temperature achieved so far for this process. Moreover, sterically hindered non-activated ortho-ortho-disubstituted electrophile was also a feasible coupling partner in cyanation. In addition, palladium-catalyzed cyanation of aryl bromides was also achieved general application of aryl halides in cyanation. The reactions were completed at 50°C under mixed solvents (water/MeCN = 1:1). This result is the mildest temperature published so far for palladium-catalyzed aryl bromides cyanation. In order to further explore cyanation, the coupling of aryl mesylates was investigated. Interestingly, the use of water as the solvent or a co-solvent was found to be essential. Moreover, this system was also applicable to the cyanation of other aryl and alkenyl tosylates. The one-pot cyanationamination sequence demonstrated the suitability of the cyanation of aryl chlorides and tosylates for the introduction of a nitrile group and manipulation of a further functional group in a synthetic pathway without isolation of the initial nitrile-substituted intermediates. These palladium catalyst systems tolerated common functional-groups: nitriles, esters, ketos, aldehydes, free amines, and heterocyclic groups are found compatible. Lastly, a palladium-catalyzed decarboxylative coupling of potassium cyanoacetate with aryl bromides and chlorides was also described. The reaction conditions featured the absence of additional strong inorganic bases and provided ester functional group tolerance. With Pd(dba)₂ and XPhos ligand as the catalyst system, α-diaryl nitriles could be obtained in good yields.<br/><br/>Description: xviii, 368 p. : ill. ; 30 cm.; PolyU Library Call No.: [THS] LG51 .H577M ABCT 2012 Yeung http://hdl.handle.net/10397/5667 Title: Characterization of the estrogenic effects of ginsenoside Rg1 : mechanism involved in achieving tissue selectivity<br/><br/>Authors: Gao, Quangui<br/><br/>Abstract: Our previous study demonstrated that ginsenoside Rg1 was a unique class of phytoestrogens which activated estrogen-like activities without direct interaction with the estrogen receptor (ER). It could initiate activation of the estrogen response element (ERE) via phosphorylation of MEK1/2 and ERα in MCF-7 cells. The present study aims to investigate if Rg1 could exert tissue-selective estrogenic effects in ER-positive target tissues and the molecular mechanism involved in its tissue-selective estrogenic effects. The short-term and long-term estrogenic effects of Rg1 were investigated in 21-day-old immature female CD-1 mice and 6-month-old ovariectomized C57BL/6J mice, respectively. The signal transduction pathways that mediate the estrogenic actions of Rg1 were investigated in MCF-7 cells and rat osteoblastic UMR106 cells in comparison to that of 17β-estradiol and estren which was a novel pathway-selective ER ligand. Additionally, MCF-7 cells and SKBR-3 cells were used to evaluate the role of GPR30 in mediating the estrogenic actions of Rg1.; Our results demonstrated that the estrogenic actions of Rg1 were distinct from those of 17β-estradiol and its effects were tissue selective. The potent estrogenic effect of Rg1 was only observed in mammary gland in immature female CD-1 mice. Chronic administration of Rg1 did not result in bone protective effects and unwanted simulation of reproductive tissues in OVX mice model in a way that was distinct from 17β-estradiol which exerted bone protective effects and also the stimulatory effects in uterus. However, Rg1 exerted potential anti-apoptotic effects on cardiovascular tissues and estrogenic effects on brain tissues. In addition, we demonstrated that Rg1, but not estren, failed to exert stimulatory effects in UMR106 cells with expressed lower level of ER, suggesting that the estrogenic effects of Rg1 in bone may require higher abundance of ER. For the molecular mechanisms study, differential signaling pathways were involved in mediating the estrogenic actions of Rg1 in MCF-7 cells in comparison to 17β-estradiol and estren. 17β-estradiol decreased ERα protein expression in MCF-7 cells, but not Rg1 and estren. 17β-estradiol increased ERα Ser 118 phosphorylation both in the cytoplasm and nucleus, especially in the nucleus. Rg1 increased ERα Ser 118 phosphorylation pricipally in the cytoplasm. Estren increased ERα Ser 118 phosphorylation pricipally in the nucleus. For the estrogen-realted pS2 gene expression, both 17β-estradiol and Rg1 increased pS2 mRNA expression in MCF-7 cells, while estren decreased pS2 mRNA expression. Additionally, both 17β-estradiol and Rg1 induced the recruitment of co-activator SRC-1 to ERE-containing pS2 promoter, but not estren. Furthermore, we are the first to report the possible involvement of GPR30 pathway on the activation of MEK1/2 by Rg1 in MCF-7 cells. In conclusion, the estrogenic effects of Rg1 might be tissue selective. The rapid ER-dependent signaling pathway was involved in the tissue-selective estrogenic effects of Rg1. Differential ER-dependent signaling pathways were involved in the estrogenic effects of 17β-estradiol, Rg1 and estren in MCF-7 cells. Additionally, GPR30 pathway was involved in mediating the estrogenic actions of Rg1. The present study provides new insights to understand the molecular action of ginsenoside Rg1 and its potential application for management of postmenopausal symptoms.<br/><br/>Description: xxxi, 288 p. : ill. (some col.) ; 30 cm.; PolyU Library Call No.: [THS] LG51 .H577P ABCT 2012 Gao http://hdl.handle.net/10397/5645 Title: Polyethylenimine-based amphiphilic core-shell nanoparticles: study of gene delivery and intracellular trafficking<br/><br/>Authors: Siu, Yuen Shan; Li, Lijun; Leung, Man-fai; Lee, K. L. Daniel; Li, Pei Pauline<br/><br/>Abstract: Amphiphilic core-shell nanoparticle, which is composed of a hydrophobic core and a branched polyethylenimine (PEI) shell, has been designed and synthesized as a novel gene delivery nanocarrier. In our previous study, we demonstrated that the core-shell nanoparticle was not only able to efficiently complex with plasmid DNA (pDNA) and protect it against enzymatic degradation, but also three times less cytotoxic, and threefold more efficient in gene transfection than branched 25 kDa PEI. This paper reports our further studies in the following three aspects: (1) the ability of the PEI-based nanoparticles to deliver gene in various mammalian cell lines; (2) intracellular distributions of the nanoparticles and their pDNA complexes in HeLa cells; and (3) incorporation of nuclear targeting agent into the nanoparticle/pDNA complexes to enhance the nuclear targeting ability. The PEI-based nanoparticles were able to transfect both human and non-human cell lines and their transfection efficiencies were cell-dependent. Within our four tested cell lines (MCF-7, BEL 7404, C6 and CHO-K1), gene transfer using PEI-based core-shell nanoparticles displayed gene expression levels comparable to, or even better than, the commercial Lipofectamine™ 2000. Confocal laser scanning microscopy showed that the nanoparticles and their pDNA complexes were effectively internalized into the HeLa cells. The in vitro time series experiments illustrated that both the nanoparticle/pDNA complexes and PEI-based nanoparticles were distributed in the cytoplasmic region after transfection for 10 and 60 min, respectively. Nuclear localization was also observed in both samples after transfection for 20 and 60 min, respectively. Incorporation of the high mobility group box 1 (HMGB1) protein for nuclear targeting has also been demonstrated with a simple approach: electrostatic complexation between the PEI-based nanoparticles and HMGB1. In the in vitro transfection study in MCF-7 cells, the expression level of the firefly luciferase gene encoded by the pDNA increased remarkably by up to eightfold when the HMGB1 protein was incorporated into the nanoparticle/pDNA complexes. Our results demonstrate that the PEI-based core-shell nanoparticles are promising nanocarriers for gene delivery.<br/><br/>Description: DOI: 10.1007/s13758-011-0016-4 http://hdl.handle.net/10397/5618 Title: Conditional inactivation of Pten with EGFR overexpression in Schwann cells models sporadic MPNST<br/><br/>Authors: Keng, Wee-Keong Vincent; Watson, Adrienne L.; Rahrmann, Eric P.; Li, Hua; Tschida, Barbara R.; Moriarity, Branden S.; Choi, Kwangmin; Rizvi, Tilat A.; Collins, Margaret H.; Wallace, Margaret R.; Ratner, Nancy; Largaespada, David A.<br/><br/>Abstract: The genetic mechanisms involved in the transformation from a benign neurofibroma to a malignant sarcoma in patients with neurofibromatosis-type-1- (NF1-)associated or sporadic malignant peripheral nerve sheath tumors (MPNSTs) remain unclear. It is hypothesized that many genetic changes are involved in transformation. Recently, it has been shown that both phosphatase and tensin homolog (PTEN) and epidermal growth factor receptor (EGFR) play important roles in the initiation of peripheral nerve sheath tumors (PNSTs). In human MPNSTs, PTEN expression is often reduced, while EGFR expression is often induced. We tested if these two genes cooperate in the evolution of PNSTs. Transgenic mice were generated carrying conditional floxed alleles of Pten, and EGFR was expressed under the control of the 2′,3′-cyclic nucleotide 3′phosphodiesterase (Cnp) promoter and a desert hedgehog (Dhh) regulatory element driving Cre recombinase transgenic mice (Dhh-Cre). Complete loss of Pten and EGFR overexpression in Schwann cells led to the development of high-grade PNSTs. In vitro experiments using immortalized human Schwann cells demonstrated that loss of PTEN and overexpression of EGFR cooperate to increase cellular proliferation and anchorage-independent colony formation. This mouse model can rapidly recapitulate PNST onset and progression to high-grade PNSTs, as seen in sporadic MPNST patients.<br/><br/>Description: DOI: 10.1155/2012/620834