Structural Influences on the Photochemistry and Photophysical Properties of p-Phenylene Ethynylenes: Aggregation Effects and Solvent Interactions

Compounds based on the p-phenylene ethynylene backbone with pendant charged groups, known as conjugated polyelectrolytes, have been of particular interest in recent years due to their solubility in water, sensing properties, and biocidal activity against bacteria, viruses, and fungi. A series of oligomers based on these polymers were synthesized (OPEs), and several interesting questions about their photophysical and biocidal properties were raised by earlier experimental observations, which are addressed by this dissertation. The study initially focuses on the influence of the backbone length and presence of carboxyester substituents on the photophysical properties of the OPEs. Next, the photochemistry of the OPEs is explored as the products and mechanisms are elucidated through isotopic studies with mass spectrometry, revealing that photo-protonation by water and addition of oxygen across the triple bond are the two dominant initial mechanisms of all major pathways in aqueous solution. Finally, the aggregation of OPEs with is studied in two systems: surfactants and model bacterial membranes. The placement of the ionic alkyl substituents played a dominant role in determining the outcome of molecular interactions and type of aggregates which resulted between OPEs and both systems. Biophysical simulations of the interactions between OPEs and these two systems provided mechanistic insight into the mechanism of bacterial membrane disruption and the attenuation of photodegradation observed with OPE-surfactant complexes. In addition to determining the OPEs could be protected from photolysis and the structural basis for aggregate type, surfactant complexation was used to form a biocidal complex from a non-biocidal anionic OPE. The work presented will be of great use for future developments in sensors, biocides, photo-resistant materials, and drug delivery applications

Polarised secretion of leukaemia inhibitory factor

Leukaemia inhibitory factor (LIF) is a cytokine that is active on a wide variety of cells. Multiple LIF transcripts have been described. The transcripts LIF-D and LIF-M encode different signal peptides, which in mouse have been associated with differential localisation of the mature protein. LIF-D is associated with a freely diffusible protein, whereas the LIF-M is associated with the extracellular matrix. The polarity of LIF secretion has yet to be described and could illuminate the mechanisms of LIF localisation. Here the polarised endogenous secretion of human LIF and IL-6 in Caco-2 cells was characterised under normal culture conditions and following induction with IL-1b. Whether the apical or basolateral membrane was stimulated influenced the pattern of secretion (LIF: Unstimulated, 59% basolateral. Dual stimulation, 68% basolateral. Basolateral stimulation, 79% basolateral. Apical stimulation, 53% basolateral). IL-6 displayed a similar dependence on the site of stimulation but was predominantly secreted at the membrane that was stimulated. To determine the effect of the alternate signal peptides on the polarity of LIF secretion, LIF was epitope tagged with FLAG. Epitope-tagging with FLAG was used to separate endogenous from exogenous protein expression. However, despite the normal biological activity of LIF-FLAG and detection of the FLAG in a western blot, detection of the LIF-FLAG under non-reducing conditions was not observed, and therefore it was unsuitable for secretion studies. Untagged LIF was expressed exogenously in Madin-Darby canine kidney (MDCK) cells under the control of a tetracycline response promoter that allowed a variety of LIF expression levels to be tested. Exogenous murine LIF was secreted predominantly from the apical (60%) membrane of MDCK cells irrespective of the signal peptide expressed

Characterization of site-specific GPS errors using a short-baseline network of braced monuments at Yucca Mountain, southern Nevada

We use a short-baseline network of braced monuments to investigate site-specific GPS effects. The network has baseline lengths of ∼10, 100, and 1000 m. Baseline time series have root mean square (RMS) residuals, about a model for the seasonal cycle, of 0.05–0.24 mm for the horizontal components and 0.20–0.72 mm for the radial. Seasonal cycles occur, with amplitudes of 0.04–0.60 mm, even for the horizontal components and even for the shortest baselines. For many time series these lag seasonal cycles in local temperature measurements by 23–43 days. This could suggest that they are related to bedrock thermal expansion. Both shorter-period signals and seasonal cycles for shorter baselines to REP2, the one short-braced monument in our network, are correlated with temperature, with no lag time. Differences between REP2 and the other stations, which are deep-braced, should reflect processes occurring in the upper few meters of the ground. These correlations may be related to thermal expansion of these upper ground layers, and/or thermal expansion of the monuments themselves. Even over these short distances we see a systematic increase in RMS values with increasing baseline length. This, and the low RMS levels, suggests that site-specific effects are unlikely to be the limiting factor in the use of similar GPS sites for geophysical investigations

Characterization of Longitudinal Splitting and Fiber Breakage in Gr/Ep using Acoustic Emission Data

A composite tensile test specimen was designed such that fiber breakage and longitudinal splitting occurred at a known position in the specimen. By studying the acoustic signature of each failure mechanism distinct characteristics in the data were identified that uniquely related the acoustic emission parameters with either fiber breakage or longitudinal splitting

Draft Genome Sequences of Macrococcus caseolyticus, Macrococcus canis, Macrococcus bohemicus, and Macrococcus goetzii

peer-reviewedHere, we present the draft genome sequences of 14 strains of 4 species of the genus Macrococcus. These strains were isolated from bovine milk and tongue samples obtained during a screening program

Draft Genome Sequences of the Type Strains of Six Macrococcus Species

peer-reviewedWe report here the draft genome sequences of Macrococcus bovicus ATCC 51825T, Macrococcus carouselicus ATCC 51828T, Macrococcus equipercicus ATCC 51831T, Macrococcus brunensis CCM4811T, Macrococcus hajekii CCM4809T, and Macrococcus lamae CCM4815T. The availability of the genome sequences of these species will enable cross-species comparison, which could lead to a more comprehensive understanding of organisms of the Macrococcus genus

Toxic structures: Speculation and lead exposure in Detroit\u27s single-family rental market

Foreclosure sales permitted investors to purchase large volumes of low-cost residential properties after the last financial crisis, reshaping patterns of property ownership in low-income housing markets across the US. This study links post-foreclosure property acquisitions by investor-landlords to subsequent lead poisoning cases among children under age six living in Detroit, Michigan. We find that the odds of exhibiting elevated blood lead levels (≥ 5 μg/dL) are higher for children living in investor-owned homes purchased through tax foreclosure sale. These findings highlight the potential for property speculation in post-foreclosure housing markets to exacerbate severe and racialized burdens of excess lead toxicity in low-income communities