Thesis advisor: James P. Morken / Described herein are three distinct projects centered on the formation and use of carbon-boron bonds. In the first, the enantioselective platinum-catalyzed 1,4-diboration of trans-1,3-dienes is advanced in both selectivity and scope through the development of a novel class of electron rich chiral monodentate phosphines. Under the action of the new ligands, highly selective diboration is maintained at reduced loadings of catalyst. Secondly, enantioenriched 1,2-bis(pinacol boronates) are engaged in regioselective Suzuki-Miyaura cross-coupling with aryl and vinyl electrophiles. A tandem diboration cross-coupling sequence is successfully implemented to afford homobenzylic and homoallylic pinacol boronates directly from terminal olefins, which subsequently undergo oxidation, amination or homologation of the remaining carbon-boron bond to arrive at a range of enantioenriched products. Lastly, aryl electrophiles containing tethered allylboronate units undergo efficient intramolecular coupling in the presence of a chiral palladium catalyst to give enantioenriched carbocyclic products. / Thesis (PhD) — Boston College, 2014. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

A dissertation submitted in fulfilment of the requirements for the degree of Master of Science at the University of the Witwatersrand. Johannesburg February 1994 / Glutathione S-transferases are multifunctional intracellular proteins. They catalyse the conjugation of glutathione to endogenous'or foreign electrophiles, and also bind non-substrate ligands. Class Pi glutathione S-transferase (pGSTPl~l) was purified from porcine lung to a specific. activity of 6.63p.ffiol/min/mg. The homodimeric protein has a molecular weight of about 4~.7kD and an isoelectric point of 8.6. Anionic ligand-binding properties of this isoenzyme were investigated. Steady-state fluorescence methods were used to determine ~ values for 8-anilino··l~naphtha1enesulphonic acid (K, == 17.1p.M and 11.1J.tM using fluorescence enhancement techniques and quenching techniques respectively), bromosulphophtbalein (Kcl=1.1p.M at pH 6.5 and 2.4/jM at pH 7.5) and glutathione {~=1201I.M). The affinity of bromosulphophthalein for the enzyme, in the presence of 10mM glutathione was slightly enhanced (~=O.7.uM at pH 6.5). The energy transfer betwecz the protein's tryptophan residues and 8-anUino-l-naphthalene sulphonic acid was observed and found to be about 56% efficient. The impact of ligand binding on both protein structure and catalytic activity were assessed. Kinetic studies show that the active site of the enzyme is not the primary binding site for the non-substrate ligands, but that the binding of bromosulphophthalein and to a lesser extent 8~ani1ino-l-!.~phtha1ene sulphonic acid, does affect the active site of the enzyme, especially aner saturating concentrations of the ligand. This may be the result of a small ligand-induced conformational change. Fluorescence studies also indicate that the primary site for anionic ligand binding is not in close proximity to either Trp28 or Trp38 in domain I, Competition studies indicated that the two anionic ligands bind the Same site, < Prorein fluorescence, chemical modification « and size-exclusion HPLC data indicate that ligand binding does 110t induce gross conformational changes in the protein.

Thesis advisor: Kian L. Tan / General and efficient methods for the selective hydroformylation of allylic alcohols and amines utilizing a directing group approach. / Thesis (MS) — Boston College, 2009. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

L'introduction d'atomes d'azote sur des squelettes organiques reste une étape clé pour la synthèse de molécules bioactives alcaloïdes. Depuis quelques années, l'insertion catalytique de nitrène sur les alcènes ou pour la fonctionnalisation des liaisons C-H est devenue un outil indéniable pour une telle introduction. Cependant, les systèmes catalytiques homogènes habituellement utilisés pour cette transformation présentent des inconvénients tels que la stabilité ou la séparation après réaction. Des catalyseurs supportés recyclables sont alors apparus comme une alternative intéressante pour surmonter ces problèmes. Dans le cadre de notre intérêt continu pour le développement de méthodologies durables, nous avons conçu de nouveaux catalyseurs valorisables efficaces, conformes aux principes de la chimie verte. Ici, la première insertion de nitrène pour l'aziridination en utilisant une nanoferrite chargée de cuivre réutilisable comme catalyseur sera présentée. Les propriétés magnétiques des nanoparticules permettent une récupération facile de ces catalyseurs avec un simple aimant externe. Nous montrerons que les catalyseurs peuvent être réutilisés 5 fois avec une conversion totale du styrène et de bons rendements, même après 5 essais. Les investigations après caractérisation complète ont montré une réduction de la charge de cuivre au fur et à mesure des cycles, ce qui peut être dû à un ancrage faible. Ce résultat nous incite à explorer différents linkers entre les nanoparticules magnétiques et le cuivre afin de diminuer cette lixiviation. Plusieurs lieurs présentant des fonctions différentes d'ancrage MNP et de chélation de Cu seront présentés. En outre, l'extrapolation réussie de cette méthodologie à des dérivés de styrène substitués pauvres en électrons ou riches en électrons sera démontrée, ainsi que l'aziridination d'oléfines à longue chaîne qui seront exposées / Introduction of nitrogen atoms onto organic skeletons remains a key step for the synthesis of alkaloid bioactive molecules. Since a few years, catalytic nitrene insertion on alkenes or for C-H bond functionalization has emerged as an undeniable tool for such introduction. However, homogeneous catalytic systems usually used for this transformation present some drawbacks such as stability, or separation after reaction. Recyclable supported catalysts have then arisen as a valuable alternative to overcome these issues.As part of our continued interest for the development of sustainable methodologies, we designed new and efficient recoverable catalysts fitting by the way the green chemistry principles. Here, the first nitrene insertion for aziridination using a reusable copper-loaded nanoferrite as catalyst will be presented. Magnetic properties of the nanoparticles allow an easy retrieval of those catalysts with a simple external magnet. We will show that the catalysts could be reused for 5 times with total conversion of styrene and good yields, even after 5 runs.Investigations after full characterization showed a reduction of copper loading as the runs, which can be due to a weak anchoring. This result prompts us to explore different linkers between magnetic nanoparticles and copper in order to decrease this leaching. Several linkers exhibiting different MNP-anchoring and Cu-chelating functions will be presented. Also, the successful extrapolation of this methodology to electron-poor or electron-rich substituted styrene derivatives will be demonstrated as well as the aziridination of long chain olefins which will be exhibited.

No description available.

Cytotoxic T lymphocytes (CTL) are differentiated CD8+ T cells that eliminate virally infected cells and tumor cells. CTL lyse target cells by at least two distinct mechanisms: degranulation of cytolytic molecules and cell surface expression of Fas ligand (FasL), which induces apoptosis of Fas-expressing target cells. In addition to their defense function, these two cytolytic mechanisms also play crucial roles in homeostatic regulation and contribute to pathogenesis in many different model systems. To fully exploit killer cells in tumor and virus elimination, or dampen the immune response in, for example, autoimmune diseases, it is essential to understand the mechanisms that CTL employ to destroy target cells. In contrast to the well-characterized degranulation mechanism, the regulation of FasL expression on the CTL cell surface remains elusive and even controversial. The prevailing model at the time I initiated my studies was that FasL is stored in cytolytic granules and that FasL cell surface expression would be subject to the same controls as degranulation. In this thesis, I revealed for the first time that there are two waves of FasL cell surface expression upon target cell engagement, which are differentially regulated by TCR signaling and perform distinct roles in CTL mediated responses. I demonstrated that CTL degranulation and FasL lytic mechanisms are fully independent with respect to stored component localization and regulation. Finally, based on cell fractionation and imaging studies, I suggested that FasL is stored in a recycling endosome associated compartment, which is located in a special niche between the ER and mitochondria and uses a novel microtubule-independent secretory mechanism to translocate to the cell surface. Together, these findings provide important insight into the regulation and role of FasL in CTL mediated responses. / Immunology

A series of compounds, 7-8 and 20-25, were tested as competitive inhibitors of 2,5-dihydroxyacetanilide epoxidase I (DHAE I) and DHAE II. A Hammett plot was constructed for each enzyme to determine the effect of electron density on inhibition. DHAE I gave a linear, highly correlated plot (r²=0.91) that signifies the importance of the amide oxygen in 1 on substrate binding. The plot for DHAE 11 is curved showing the greatest degree of inhibition with 7 suggesting steric factors within the active site control substrate binding. From these data, we conclude that each enzyme binds substrate in an opposite fashion and that this alone controls the stereochemistry of epoxide formation in 2 and 3. Alternative substrates, 26-29 and 33, were also synthesized and tested for product formation. All compounds, except 29, were accepted as alternative substrates, although the rates varied significantly. Surprisingly, 33 was accepted as an alternative substrate of DHAE II suggesting that the conformation of the amide bond in 33 is similar to the conformation required for catalytic activity in this enzyme. This information was then used to design ligands for affinity column separation of DHAE I and DHAE II from their protein mixtures. 35 and 36 were synthesized and attached to carbonyl di-imidazole activated agarose. Column I was tested three times with DHAE I enzyme preparations. The first attempt did not result in active enzyme being eluted from the column. The second attempt maintained the resin in the oxidized state. Protein was found to elute very quickly: no protein was found after fraction 4. The third attempt resulted in active enzyme in fractions 4-23. Column 2 was used twice for the attempted isolation of DHAE II from its protein mixture. The second attempt for column 2 mirrored the results for the third attempt with column 1. Neither column resulted in homogeneous enzyme by SDS-PAGE. / Graduation date: 2003

Graduation date: 1994

Objectives: Periodontal disease is a chronic inflammation resulting in periodontal attachment loss. Keratinocyte Growth Factor-1 (KGF-1) is upregulated in chronic inflammation and specifically stimulates epithelial cell proliferation by signaling through the epithelial-specific Keratinocyte Growth Factor Receptor (KGFR). First, we examined KGF-1 and KGFR expression and localization in human periodontal tissues. Second, we extended these studies by developing an in vitro mechanical wound model to mimic trauma to the periodontal pocket epithelium and examined ligand independent KGFR activation and cell migration. Methods: In our study of human gingival tissues, we used immunohistochemistry and laser capture microdissection with RT-PCR to analyze KGF-1 and KGFR expression and localization. To study ligand independent KGFR phosphorylation, KGFR internalization along the wound edge was imaged using immunohistochemical staining and KGFR phosphorylation confirmed using immunoprecipitation with western blotting. Wounding induced oxidative stress was detected using DCFH-DA (2',7'-dichlorofluorescin diacetate) and modulated by pretreatment with an antioxidant. Changes in migration were examined in the presence or absence of pathway specific inhibitors. Results: KGF-1 protein localized to areas of junctional and basal oral epithelial cells was significantly increased in periodontal pocket epithelium (p<0.01) and oral epithelium (p<0.05) of disease-associated tissues. KGFR localized to the junctional and the parabasal cells of oral epithelium, and was increased in disease-associated pocket epithelium (p<0.05). Laser capture microdissection with RT-PCR confirmedKGF-1 and KGFR were specifically expressed by connective tissue and epithelium, respectively. In our cell culture model, mechanical wounding induced ligand independent KGFR activation. ROS (Reactive Oxygen Species) generation along the wound edge was associated with KGFR activation and scavenging of ROS reduced KGFR phosphorylation. The c-Src family inhibitor, PP1, significantly inhibited KGFR phosphorylation. Functionally cell migration was reduced by PP1 (82.7%), SU5402(70%) and PD98059 (57%). Conclusions: KGF-1 and KGFR proteins are expressed in health but significantly induced in human diseased periodontal tissues. Microwounding associated generation of ROS mediates KGFR phosphorylation via c-Src kinase signaling and induced wound edge cell migration. Therefore, regulation of epithelial cell behavior associated with the onset and progression of periodontal disease may possibly be mediated by two related but distinct mechanisms. (1) Ligand-dependent activation of KGFR due to upregulation of KGF-1. (2) Ligand-independent activation of KGFR due to chronic microwounding.

none