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A novel type of white light emitting semiconductor quantum dot was characterized at the ensemble and single-molecule level. This kind of semiconductor nanocrystal can be made into white light emitting diodes, which have the potential to replace conventional lighting sources. The quantum dots used in this thesis consisted of a cadmium selenide (CdSe) core, capped with ZnS, and have a surface polymer coating of poly(acrylic acid) (PAA). We have characterized the quantum dot size distribution by using dynamic light scattering (DLS), transmission electron microscopy (TEM), atomic force microscopy (AFM) and UV-Vis spectroscopy. Based on these measurements, it is clear that the white quantum dots are polydisperse, with a core size of 2.4 ± 0.5 nm, though the polymer coating swells considerably in aqueous solution. In order to explore the optical properties, the absorption and emission spectra of the ensemble quantum dots solution were measured and compared to “standard” commercial quantum dots. The emission spectrum of the white quantum dots showed two peaks, a strong blue emission peak and a weaker red emission peak. The fluorescence quantum yield of the white quantum dots was found to be less than that of commercial quantum dots. To explore the behavior of individual quantum dots, spatially-resolved single-molecule images were obtained by a dual-view single molecule fluorescence microscopy with a beam splitter which can separate the emission into red and blue components. It was found that individual white CdSe nanocrystals have a broad emission spectrum and the samples did not consist of a mixed population of red emitters and blue emitters. These results suggest that these white light emitting quantum dots can be used for pure white light LEDs and are a good candidate for the replacement for conventional lighting sources.

This thesis examines the use of anionic nitrogen chelate ligands in coordination-driven self-assembly and small molecule activation. The two classes of anionic nitrogen chelate ligands that were explored are β-diiminate and 4,5-diazafluorenide derivatives. Chapter 2 deals with Pd β-diiminate chemistry. Chloro-bridged dimers served as versatile starting materials, and their reactivity toward pyridine and arylboronic acids was explored. An unusual transmetallation reaction with arylboronic acids triggered the self-assembly of tetrapallada-macrocycles. The formation of the self-assembled tetrapallada-macrocycles is through the generation of new Pd-C bonds. Chapter 3 deals with 4,5-diazafluorenide as an actor ligand in CO2 activation. A reversible formal insertion of CO2 into a remote ligand C-H bond was discovered. A variety of spectator metal centres were used to tune the reactivity of the actor ligand toward CO2. The spectator metal centre could even be replaced entirely with an organic group allowing for the first metal-free reversible tandem CO2 and C-H activation. Chapter 4 deals with the reactivity of dinuclear Rh 4,5-diazafluorenide-9-carboxylate complexes with dihydrogen in an attempt to reduce the trapped CO2 moiety. A series of stepwise stoichiometric reactions with H2, NMR experiments at low temperatures with added PPh3 or CO2, along with 13C-labelling experiments were conducted in an attempt to identify the products of this reaction and gain some mechanistic insight. Chapter 5 deals with using ambidentate 4,5-diazafluorene derivatives to synthesize linkage isomers, heterobimetallic complexes, and self-assembled macrocycles. The synthesis a new ligand family, 3,6-substituted 4,5-diazafluorene ligands is presented, along with coordination chemistry towards a {RuCp*}+ fragment. Finally in Chapter 6 the coordination chemistry of 3,6-diaryl substituted 4,5-diazafluorene derivatives was explored with the goal of generating low-coordinate species for the activation of small molecules, especially N2. The synthesis of the first trialkylborohydride complex of vanadium is presented.

Adenoviruses are common pathogens all over the world. The majority of the population has at some point been infected with an adenovirus. Although severe disease can occur in otherwise healthy individuals an adenovirus infection is most commonly self limited in these cases. For immunocompromised individuals however, adenoviruses can be life-threatening pathogens capable of causing disseminated disease and multiple organ failure. Still there is no approved drug specific for treatment of adenovirus infections. We have addressed this using a unique whole cell viral replication reporter gene assay to screen small organic molecules for anti-adenoviral effect. This RCAd11pGFP-vector based assay allowed screening without any preconceived idea of the mechanism for adenovirus inhibition. As a result of the screening campaign 2-[[2-(benzoylamino)benzoyl]amino]-benzoic acid turned out to be a potent inhibitor of adenoviral replication. To establish a structure-activity relationship a number of analogs were synthesized and evaluated for their anti-adenoviral effect. The carboxylic acid moiety of the molecule was important for efficient inhibition of adenovirus replication. There are 54 adenovirus types characterized today and these are divided into seven species, A-G. The receptors used by species B and other adenoviruses are not fully characterized. CD46 is a complement regulatory molecule suggested to be used by all species B types and some species D types but this is not established. We have designed a new bioassay for assessment of the interaction between adenoviruses and CD46 and investigated the CD46-binding capacity of adenovirus types indicated to interact with CD46. We concluded that Ad11p, Ad34, Ad35, and Ad50 clearly bind CD46 specifically, whereas Ad3p, Ad7p, Ad14, and Ad37 do not. CD46 is expressed on all human nucleated cells and serves as a receptor for a number of different bacteria and viruses. Downregulation of CD46 on the cell surface occurs upon binding by some of these pathogens. We show that early in infection Ad11p virions downregulate CD46 upon binding to a much higher extent than the complement regulatory molecules CD55 and CD59. These findings may lead to a better understanding of the pathogenesis of adenoviruses in general and species B adenoviruses in particular and hopefully we have discovered a molecule that can be the basis for development of new anti-adenoviral drugs.

A series of small molecules was synthesized to probe three protein targets in order to elucidate the key small molecule-protein interactions required for potency. Triclosan is an antibacterial compound that has surfaced as a potential environmental hazard and is hypothesized to cause perturbations in the thyroid hormone response of frogs. Using a C-fin assay and a GH3 cell line, our work suggests that triclosan itself may not in fact be the cause of the observed endocrine disruptions. Instead, methyl triclosan (a result of biological methylation during waste water treatment) was shown to disrupt the thyroid hormone response in tadpoles. Secondly, a set of probes was designed based on a cyclopentane scaffold derived from the known neuraminidase inhibitor peramivir. Kinetic assays using both a recombinant neuraminidase protein and an inactivated sample of influenza virus showed that the guanidine group contributes a 10 fold increase in potency while the α-hydroxyl group was observed to have little to no effect. This result suggests that future neuraminidase drug design based on a cyclopentane scaffold may forgo the use of both the guanidinium group and the hydroxyl group to potentially increase the oral availability of these drugs while sacrificing little in the way of potency. Finally, a series of truncated analogues related to the western half of the natural product didemnaketal A was synthesized. These compounds will be used as probes to better understand the mechanism of didemnaketal-mediated protease inhibition. It is hypothesized that a more rigid structure (due to molecular gearing enforced by the presence of additional methyl groups, relative to previously examined analogues) will increase the potency of these molecules toward HIV-1 protease and may lead to new information for designing next-generation dissociative inhibitors. Work was also begun toward the total synthesis of the natural product itself. / Graduate

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No description available.

Single-molecule fluorescence spectroscopy techniques such as Fluorescence Correlation Spectroscopy (FCS) and single-molecule Förster Resonance Energy Transfer (smFRET) not only possess an unprecedented high sensitivity but also have high temporal and spatial resolution. Therefore, they have an immense potential both in investigation of fundamental biological principles and in clinical applications. FCS analyses are based on both theoretical approximations of the beam geometry and assumptions of the underlying molecular processes. To address the accuracy of analysis, firstly the experimental conditions that should be fulfilled in order to obtain reliable physical parameters are discussed and the input parameters are carefully controlled accordingly to demonstrate the performance of FCS measurements on our home-built confocal multiparameter photon-counting microscope in several in vitro and in-vivo applications. Secondly, we performed a comprehensive FCS analysis of rhodamine family of dyes to evaluate the validity of assigning the correlation relaxation times to the time constant of conformational dynamics of biomolecules. While it is the common approach in literature our data suggests that conformational dynamics mainly appear in the correlation curve via modulation of the dark states of the fluorophores. The size and shape of the folded, unfolded and chemically-denatured states of the N-terminal Src-homology-3 of downstream of receptor kinases (DrkN SH3) were investigated by FCS and smFRET burst experiments. Based on the data, we conclude that a considerable sub-population of the denatured protein is in a closed loop state which is most likely formed by cooperative hydrogen bonds, salt bridges and nonpolar contacts. As a clinical application, we developed and characterized an ultrasensitive capillary electrophoresis method on our multiparameter confocal microscope. This allowed us to perform Direct Quantitative Analysis of Multiple microRNAs (DQAMmiR) with about 500 times better sensivity than a commercial instrument. Quite remarkably, we were able to analyze samples of cell lysate down to the contents of a single cell.

The oncogenic transcription factor STAT3 is aberrantly activated in over 70% of human tumours, including Multiple myeloma (MM). The present studies use both genetic and chemical tools to validate STAT3 as a therapeutic target, and demonstrate the anti-MM activity of a novel small molecule STAT3 inhibitor, BP-4-018. We show that shRNA-mediated STAT3 knockdown induces apoptosis in human myeloma cell lines (HMCLs). We translate these findings to a therapeutically relevant setting by demonstrating the broad anti-MM activity of BP-4-018 against HCMLs and primary patient samples, and demonstrate that BP-4-018 remains active against HMCLs co-cultured with bone marrow stroma. Inhibiting STAT3 via shRNA knockdown and BP-4-018 suppresses STAT3 transcriptional activity and down-regulates anti-apoptotic and proliferative STAT3 target genes. Finally, we show that BP-4-018 has activity in vivo, both alone and combined with subtherapeutic doses of bortezomib, without significant toxicities. Taken together, these data support the utility of STAT3 inhibitors for MM treatment.