The filamentous cyanobacteria Nostoc punctiforme ATCC 29133 is a model species fordevelopment of sustainable production methods of numerous compounds. One of its uniquefeatures is the anaerobic environment of the strains nitrogen fixing heterocyst cells. To be ableto properly utilize this environment, more knowledge regarding what regulates cell specificexpression is required. In this study, three motifs of the NsiR I promoter of Anabaena sp.PCC 7120 was studied in this system utilizing YFP-fluorescence as a reporter to determinetheir impact on spatial expression pattern. Investigations were performed on immobilizedcells with the use of confocal microscopy and results point towards sigma factor regulation.

This dissertation describes the characterization of layer-by-layer silica and titania coatings deposited using a protamine-induced method. It was found that silica coatings were thinner and more porous than titania coatings. These coatings were functionalized by immobilizing modified Glucose oxidase during the layer-by-layer buildup. The enzyme was found to retain higher activity in silica versus titania, with full retention of activity observed in one configuration. Immobilization in both materials resulted in enhanced thermal stability and proteolytic protection. The enzyme-functionalized coatings were then modified by the immobilization of silver nanoparticles to the exterior, and this biological/inorganic composite was tested for its antimicrobial activity against E. coli and S. aureus. Against E. coli the composite worked in a synergistic fashion, showing more potent antimicrobial activity when compared to either agent used alone. The enzyme modification method was then extended to Laccase, which was immobilized to carbon nanotubes and characterized as a biocathode. Modified laccase returned a nearly two-fold higher current density versus the native enzyme. Finally, synthetic peptides were tested for their ability to adsorb to silica and titanium-oxide surfaces and subsequently deposit titanium-oxide coatings, in an effort to better understand the structure-function relationships of mineralizing peptides.

A key challenge in tissue engineering is overcoming cell death in the scaffold interior due to the limited diffusion of oxygen and nutrients therein. We hypothesized here that immobilizing a gradient of vascular endothelial growth factor (VEGF-165) would guide endothelial cells into the interior of the scaffold thereby enhancing angiogenesis. The protein was immobilized onto a collagen scaffold through carbodiimide chemistry by one of the three methods experimented: placing 5 µl of the solution at the center of the scaffold to create a ~2 ng/ml/mm gradient in a radial direction. D4T endothelial cells were observed to be guided by this VEGF-165 gradient deep into the center of the scaffold compared to both uniformly immobilized VEGF-165 and VEGF-free controls. We concluded that the VEGF-165 gradient scaffolds promoted the migration, and not proliferation, of cells deep into the scaffold. These gradient scaffolds provide the foundation for future in vivo tissue engineering studies.

A key challenge in tissue engineering is overcoming cell death in the scaffold interior due to the limited diffusion of oxygen and nutrients therein. We hypothesized here that immobilizing a gradient of vascular endothelial growth factor (VEGF-165) would guide endothelial cells into the interior of the scaffold thereby enhancing angiogenesis. The protein was immobilized onto a collagen scaffold through carbodiimide chemistry by one of the three methods experimented: placing 5 µl of the solution at the center of the scaffold to create a ~2 ng/ml/mm gradient in a radial direction. D4T endothelial cells were observed to be guided by this VEGF-165 gradient deep into the center of the scaffold compared to both uniformly immobilized VEGF-165 and VEGF-free controls. We concluded that the VEGF-165 gradient scaffolds promoted the migration, and not proliferation, of cells deep into the scaffold. These gradient scaffolds provide the foundation for future in vivo tissue engineering studies.

Immobilization and detoxification of chromium in the vadose zone is made possible by the existence of an effective reductant, SO2, that exists in a gaseous form at room temperature. Experimental studies were designed to characterize stoichiometry and kinetics of chromium reduction both in aqueous solutions at pH values near neutrality and in soil. First, batch experiments and elemental analyses were conducted to characterize the stoichiometry and kinetics of Cr(VI) reduction in water. The stoichiometric ratio of S(IV) removed to Cr(VI) removed ranged between 1.6 and 1.8. The overall reaction is believed to be the result of a linear combination of two reactions in which dithionate is an intermediate and sulfate is the stable oxidized product. The reaction was also rapid, with the half-time of about 45 minutes at pH 6 and about 16 hours at pH 7. A two-step kinetic model was developed to describe changes in concentrations of Cr(VI), S(IV), and S(V). Nonlinear regression was applied to obtain the kinetic parameters. The rate of reaction was assumed to be second-order with respect to [Cr(VI)] and first-order with respect to [S(IV)], and [S(V)]. The values for the rate coefficient for the first reaction (k1) were found to be 4.5 (?10%), 0.25 (?9.4%) (mM-2h-1) at pH 6 and 7, respectively. The values of the rate coefficient for the second reaction (k2) were 25 (?29%), 1.1 (? 30%) (mM-2h-1) at pH 6 and 7, respectively. The reaction rate decreased as pH increased. Experiments showed that the rate at pH 7 was lower than that at pH 6 by one order of magnitude. Second, batch experiments and elemental analyses were conducted to characterize the stoichiometry and kinetics of Cr(VI) reduction in soil. The stoichiometric ratio of S(IV) removed to Cr(VI) removed was almost 2, which is slightly higher than that for the reaction in water. This higher value may be due to S(IV) oxidation by soil-derived Fe(III). The reaction was rapid, with the half-time less than 2 minutes, which is faster than in water. The rate coefficients, k1 and k2, were 22 (?41%) and 13 (?77%) (M-2h-1), respectively.

No description available.

The unique optical properties of quantum dots (QDs) have been widely used to develop bioassays based on Fluorescence Resonance Energy Transfer (FRET). The solid-phase assays using QDs as FRET donors have numerous practical advantages, including at least 10-fold enhancement in FRET efficiency, which is not immediately explained by theoretical predictions that model energy transfer processes of QDs in two-dimensional layers. Donor-acceptor separation distance, acceptor and donor concentrations were found to influence FRET efficiency in solid-phase assays. A novel immobilization strategy was implemented which made use of the high affinity of imidazole moieties to QD shells to build solid-phase QD bioassays. A 96-well polystyrene plate is presented as a platform suitable for rapid and convenient multiplexed detection. A typical microtiter plate reader was shown to be capable of discriminating different FRET pairs to picomol detection levels of target oligonucleotides. Furthermore, the QD-FRET bioassays provided for mismatch discrimination, and multiple cycles of regeneration were also demonstrated.

The unique optical properties of quantum dots (QDs) have been widely used to develop bioassays based on Fluorescence Resonance Energy Transfer (FRET). The solid-phase assays using QDs as FRET donors have numerous practical advantages, including at least 10-fold enhancement in FRET efficiency, which is not immediately explained by theoretical predictions that model energy transfer processes of QDs in two-dimensional layers. Donor-acceptor separation distance, acceptor and donor concentrations were found to influence FRET efficiency in solid-phase assays. A novel immobilization strategy was implemented which made use of the high affinity of imidazole moieties to QD shells to build solid-phase QD bioassays. A 96-well polystyrene plate is presented as a platform suitable for rapid and convenient multiplexed detection. A typical microtiter plate reader was shown to be capable of discriminating different FRET pairs to picomol detection levels of target oligonucleotides. Furthermore, the QD-FRET bioassays provided for mismatch discrimination, and multiple cycles of regeneration were also demonstrated.

Thesis (M.Phil) - University of Queensland, 2004. / Includes bibliography.

abstract: Bacteriophage provide high specificity to bacteria; receiving interest in various applications and have been used as target recognition tools in designing bioactive surfaces. Several current immobilization strategies to detect and capture bacteriophage require non-deliverable bioactive substrates or modifying the chemistry of the phage, procedures that are labor intensive and can damage the integrity of the virus. The aim of this research was to develop the framework to physisorb and chemisorb T4 coliphage on varied sized functionalized silica particles while retaining its infectivity. First, silica surface modification, silanization, altered pristine silica colloids to positively, amine coated silica. The phages remain infective to their host bacteria while adsorbed on the surface of the silica particles. It is reported that the number of infective phage bound to the silica is enhanced by the immobilization method. It was determined that covalent attachment yielded 106 PFU/ml while electrostatic attachment resulted in 105 PFU/ml. / Dissertation/Thesis / Masters Thesis Civil and Environmental Engineering 2017