A set of three benzophenoxazine dyes, two completely soluble and one partially soluble in aqueous media, has been prepared and their spectroscopic properties examined. These dyes can be used as either donor or acceptor in synthesis of through-bond energy transfer cassettes. Structural modifications prevented aggregation in water and improved their fluorescence properties in water. Their absorption and emission were studied in both organic and aqueous media. Two of the three dyes have superior quantum yields in aqueous media as compared to other reported dyes. Improved quantum yield makes these dyes attractive candidates for biological studies in aqueous media. We have also prepared alkynes and iodo derivatives of benzophenoxazines, which can be used for synthesis of water-soluble, through-bond, energy transfer cassettes. Alkynes were prepared via Sonogashira coupling.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

In this work, novel Gd(III) complexes endowed with non-steroidal anti-inflammatory drugs (NSAIDs) were synthesised and their targeting properties towards sites of inflammation were studied in U87 xenograft and rheumatoid arthritis animal models. The Tb(III) analogues were also synthesised and their photophysical properties were studied. Six new Gd(III) DO3A-amide complexes bearing different linkers, ethylenediamine (GdL1), hexamethylenediamine (GdL2), 2,2’-oxydiethylamine (GdL3), 4,7,10-trioxa-1,13-tridecanediamine (GdL4), trans-1,4-cyclohexanediamine (GdL5), and 1,4-phenylenediamine (GdL6) were incorporated to mefenamic acid (MA) moiety, a common NSAID. The syntheses, relaxometric properties by NMR techniques, hydration number determinations by luminescence lifetime measurements, lipophilicities by UV-Vis spectrometry, serum albumin binding properties by tryptophan emission-quenching experiments, cytotoxicities by MTT assay, cellular uptake properties; MRI scans on U87 sxenograft and rheumatoid arthritis animal models, and biodistributions of these new complexes were discussed. GdL1-L6 possess one bound water molecule and GdL2-L5 show higher relaxivities than Gd-DOTA (4.21 mM?1s?1, 300 MHz, 25oC), a clinically used MRI contrast agent (CA). The relaxivities at 300 and 400 MHz respectively at 25oC are in the descending order of GdL4 (5.70 and 4.87 mM?1?1) > GdL3 (4.94 and 4.07 mM?1s?1) > GdL2 (4.60 and 4.07 mM?1s?1) > GdL5 (4.41 and 4.12 mM?1s?1) > GdL6 (3.98 and 3.31 mM?1s?1) > GdL1 (3.96 and 3.56 mM?1s?1). GdL1-L5 show low cytotoxicities towards HeLa cells at 1000 μM. The MRI scans of GdL1-L6 on U87 xenograft show strong intensity boost immediately after administration. The intensity enhancements persist for more than 90 mins and complete clearances are found after 24 h post-administration. Their MRI scans on arthritis model also show prolonged retention. It is concluded that the retention is related to the targeting on inflammatory mediators of the complexes. All complexes show superior retention and intensity enhancements in kidney, liver, tumour and arthritis joint than Gd-DOTA. GdL1-L6 are therefore potential candidates as universal MRI CAs. Three new Gd(III) DO3A-amide complexes bearing respectively benzoic acid (GdL7), salicylic acid (GdL8), and methylated salicylic acid (GdL9), one known Gd(III) DTPA-bissalicylic acid (GdL10) complex and one new Gd(III) DTPA-bismethylated salicylic acid (GdL11) were synthesised and investigated. Their syntheses, relaxivities, hydration numbers, pH dependent photophysical properties, cytotoxicities, cellular uptake properties and MRI scans on arthritis rat model were discussed. All GaL7-L11 possess one bound water molecule and show lower relaxivities than Gd-DOTA. The relaxivities at 300 MHz at 25oC are in the descending order of GdL10 (3.64 mM?1s?1) > GdL9 (3.53 mM?1s?1) > GdL11 (2.69 mM?1s?1) > GdL8 (2.10 mM?1s?1) > GdL7 (1.99 mM?1s?1). Their Tb(III) analogue (TbL7-L11) show pH dependent UV-Vis and photoluminescence spectra which are consequences of protonation or deprotonation of the carboxylic acid, hydroxyl and amide groups. It is concluded that the pH change alters energy transfer efficiency and the ligand triplet energy level. GdL7-L11 show low cytotoxicities in MTT assay. Specifically, GdL8 is examined on arthritis rat model to give a comparable intensity at the arthritis joint to Gd-DOTA but having a longer retention time. LnL8 has therefore demonstrated its potential as both a MRI CA to target inflammation sites and a pH dependent luminescence probe. / published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

Light bulbs play an indispensable role in our lives as they provide unhindered ability to see the world even during the night. Efficiency of light bulbs is becoming increasingly important, and through this experiment, light bulb efficiencies are analyzed from measurements of relative light intensity and power input of various bulbs. Furthermore, this report is aimed to increase awareness of the efficiency advantage in fluorescent bulbs and to encourage their usage in the interest of conserving energy.

No description available.

The objective of this project is to design a facility that will characterize the electrical and optical properties of both tubular and the more recent compact fluorescent tubes. The first stage of this project, which is the subject of this dissertation, was to design, build, test, and model a cylindrical light integrating chamber. An integrating chamber capable of measuring 2-metre long fluorescent tubes was built at the University of KwaZulu-Natal, South Africa. To approximate an infinitely long tube, precisely mounted planar mirrors were placed at opposite ends of the cylinder. The reflectance of diffusive reflective paint and mirrors enter into calculations and were investigated experimentally using a Jarrel-Ash optical spectrometer. The light flux was finally measured for various chamber lengths and compared with a mathematical model. Total light power output from the lamp was calculated and compared with the electrical power input, and the lamp efficiency deduced. Accurate calculations required that the light field surrounding a cylindrical diffuse source be modeled mathematically. The reflection coefficients of the mirrors were not unity and the equations had to be modified to include this effect. The mathematical model was solved using a combination of analytical and numerical techniques. The model results were compared with measurements. The final result includes a mathematical description of the integrating chamber, and a flux-density plot of the space surrounding the fluorescent tube. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2008.

No description available.

A simple and feasible method of computer colour matching involving fluorescent dyes was developed. An ordinary abridged-spectroreflectometer with polychomatic illumination and a simulated D65 xenon light source was employed for all measurements. In addition to the normal K/S constants for non-fluorescent dyes and the non-fluorescent portion of the fluorescent dye'.. constants responsible for the fluorescent portion were necessary. Two sets of equations to relate the total radiance factors of dyeings with a fluorescent dye and its concentration were developed respectively for self and compound shades where a non-fluorescent dye is admixed. Finding constants responsible for the compound shades required a number of calibration mixture dyeings. Negative K/S constants were found useful when the total radiance factor was above that for the substrate but below one hundred. Three computer programs? s were developed to deal with calibration constants for self and compound shade and also for match prediction. Optimization was used in all cases to minimize errors in total radiance factors or colour differences. Half of the actual dyeingq formulations from the predicted were visually passed by a panel of five dyers. In this study, disperse dyes on polyester were used. Moreover, a commercial matching package was studied using non-fluorescent dyes. The dyeing system affected its accuracy. The polyester/disperse dye system was better than the cotton/reactive dye system. The sample size and luminancefactor of target colours; were also studied. The accuracy was affected slightly by the latter but not the former.

The development of new drug therapies traditionally requires mass screening of thousands if not millions of substances to identify lead compounds. They are then further optimised to increase potency. The screening of the large pharmaceutical compound libraries can be incredibly expensive, with the industry responding by miniaturising the assays to smaller formats, enabling the compound screening to be automated and, importantly, eliminating assay reagents that are a major contributing cost for running large screens. A potential target for such an approach is the genetic recoding site of viruses like HIV-1 and SARS. They use programmed recoding of the genetic code to regulate the translation of necessary proteins required for viable virus production. For example HIV-1 uses a -1 frameshift mechanism to regulate the ratio of the Gag to the Pol proteins, crucial for viable virus formation. The study of recoding, including readthrough of premature termination codons have most recently used bicistronic reporters with different combinations of enzymes. The most widely used plasmid bicistronic reporter utilises a dual luciferase arrangement comprised of firefly luciferase and Renilla luciferase reporters flanking the DNA being studied. Both of the luciferase enzymatic reporters emit light in response to their respective substrates. The cost of these substrates is the major issue to using luciferase reporters for high throughput screening. My study aimed at designing and developing a bicistronic assay suitable for genetic recoding that was amenable to high throughput screening. The luciferase reporters were replaced with Green Fluorescent Protein (GFP) reporters that do not require the addition of substrates. The development of a dual GFP assay required the appropriate selection of GFP fluorophores, the best arrangement of the GFPs to maximise the ratio of relative fluorescence intensity signal to background, the optimisation of the cells and growth conditions, DNA transfection, plate reader selection, and optical filter sets. Cassettes encoding protein linkers were also incorporated into the design of the constructs to separate the fluorescent proteins spatially to facilitate unimpaired folding into their functional units within the fusion protein. The assay was further improved by moving from transient transfection to stably expressing cell lines. A viable assay was almost achieved for 96 (and 384) well plates with a Z� factor compatible with the assay being suitable for high throughput screening. The assay was used to test a small collection of compounds known to interact with the ribosome and compounds known in the literature to affect frameshifting. This proof of concept was important, since it showed that the assay, with the various modifications, optimisations and miniaturisation steps, still retained the capability of correctly measuring the -1 frameshifting efficiency at the HIV-1 recoding site, and recording compound-induced modulations to the frameshifting efficiency. The compounds cycloheximide and anisomycin, for example, were shown to decrease -1 frameshifting albeit at some expense to overall protein synthesis. The dual GFP assay was also shown to be able to measure accurately changes in the frameshift efficiency brought about by mutations to the frameshift element, and additionally, it would be suitable for the detection and study of compounds, like the recently reported PTC-124 (currently undergoing phase II clinical trial for Duchenne Muscular Dystrophy and cystic fibrosis) that increases readthrough of a UGA premature stop codon mutation. The dual GFP assay developed in this study is at most only 1/10th of the cost of a comparable dual luciferase assay, largely due to removal of assay substrates and transfection reagents. The assay has a robust Z� factor comparable to that of the dual luciferase assay, and would substantially decrease the costs of high throughput screening in situations where a bicistronic reporter is required. The HIV-1 frameshift element is such a site.

Coral reefs are a critical resource to developing and developed nations world wide. Providing shelter, food, monetary value, and a vast resource of ecological wealth, the corals of the reefs underpin an entire ecosystem. Climate change, driven by increased greenhouse gases, is raising the temperature of Earth’s waters and atmosphere, while making the planet’s oceans increasingly acidic. Brightly lit and increasingly warm tropical waters present a potentially challenging environment in which scleractinian corals grow. In attempting to cope with the competing stresses of intense photon flux density (PFD) and anomalously high sea surface temperatures, corals and dinoflagellates exhibit myriad biochemical and physiological adaptations. Pocilloporins, a diverse group of non-fluorescent green fluorescent protein (GFP) homologs found across Cnidaria and beyond, are one such adaptation within the tissues of heavily pigmented scleractinian corals. Chemically unique amongst pigments, GFP-like pigments exist as pure protein chromophores and exhibit little to no cytotoxicity when naturally occurring. This non-fluorescent class of GFP-like pigments has found popularity in biochemical and biotechnological applications, though an ecological and evolutionary explanation for the heavy conservation of pocilloporins across a broad range of scleractinian corals and related cnidaria is still a subject of scientific research and debate. This thesis supports the hypothesis that pocilloporins act as a naturally occurring photoprotective pigment in reef-building corals, specifically acting to filter and regulate the light environment within coral polyps. In examining the role of pocilloporins in Scleractinia, the need to examine environmental sources of pigment production induction and suppression, the localization of pigments within coral tissues and cells, and the ability of coral colonies to direct resource allocation with regards to pocilloporin production were identified as lines of inquiry. Briefly, for experiments examining either pocilloporin induction or suppression, the following aspects were studied: holobiont responses in the form of mRNA signal expression, host pigment isolation and analysis, dinoflagellate density and pigmentation sampling, and chlorophyll fluorescence of live corals. Blue morph Acropora aspera, common to the reef flat of Heron Island (Great Barrier Reef, Australia), were subjected to 99% shade and thermal bleaching threshold temperatures in separate attempts to suppress pocilloporin expression, while red morph Montipora monasteriata was transplanted at equivalent depth from their natural cave environments to exposed portions of the spur and groove formations of the northern face of Wistari Reef (Great Barrier Reef, Australia). Both ambient temperature and heat-stressed A. aspera were concurrently collected during the thermal stress experiment and placed in preservatives for immuno-histochemical localization of pocilloporins with their tissues. Finally, radio-labelled glycine, a very common amino acid in the primary sequence of pocilloporin, was injected into artificially injured tan morph Montipora monasteriata, also on the northern face of Wistrai Reef to study the uptake of dissolved organic materials (DOM) and incorporation of metabolic resources into newly generated pigments. Pocilloporins proved easier to induce in this work than suppress, and the location of these pigments in A. aspera tissues suggests a potential mechanism. The data demonstrated the presence of pocilloporins in the most directly exposed epidermal and gastrodermal tissues of the coral polyp, specifically the outermost layers of epidermis and gastrodermal layers bordering directly upon the gastrovascular cavity. Closer inspection through anti-pocilloporin-gold stained TEM images was highly suggestive of pocilloporin secretion in coral mucus, a theory separately supported by observations of coral mucus in collected live corals. Neither suppression experiment induced heavy mucus sloughing in A. aspera, so despite multi-fold reductions in pocilloporin mRNA as a result of applied stimuli, the continued presence of pocilloporin aaCP592 in blue morph A. aspera is not surprising. Conversely, pocilloporin msCP576 in plating Montipora monasteriata was induced in response to both general increases in PFD and specific increases of PFD at the sites of physical injury. Additionally, tan morph Montipora monasteriata demonstrated the capacity to collect and allocate DOM from the environment to assist in the production of new pigments and tissues, an energetically expensive process. The reduction of the orange-red spectrum in favour of the blue light ranges is generally beneficial to the photosynthetic systems of both higher plants and the resident dinoflagellates of corals. msCP576 and aa592, both positively identified as pocilloporins within this work, absorb within the orange-red region and apparently act as a photoprotective filter in all exposed surfaces of heavily pigmented corals, enhancing the blue spectrum of incident and reflected PFD and generally regulating the internal light environment.