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Hydroxymethylglutaryl-CoA synthase (HMG-CoA synthase) catalyzes the formation of HMG-CoA from acetyl-CoA and acetoacetyl-CoA. F-244 (1), a naturally occurring J3-lactone isolated from Fusarium sp. ATCC 20788 and other species, is known to be a potent and specific inhibitor ofHMG-CoA synthase isolated from rat liver. 1Ji,, HO,.,._.. .. , '• .. ,....13_.,., ;=( 0 14 0 0 (1) (2) This thesis describes the 48 fold purification of HMG-CoA synthase from bakers yeast in a three step procedure involving ethanol fractionation followed by ammonium sulfate precipitation and then hydroxylapatite chromatography. This procedure was found to be reproducible and yields a preparation of specific activity 0.14 units (j...tmolfmin)/mg in an overall yield of 8%. In our study, F-244 was found to be a potent irreversible inhibitor of HMGCoA synthase isolated from bakers yeast, with an IC50 value of 0.009 j...tM. This value is almost identical to the inhibitory activity of F-244 on rat liver HMG-CoA synthase that has been reported in the literature. Tritium labeled F-244 was prepared, for the first time, by feeding methyl-[3H]methionine to cultures of Fusarium sp. The [15, 16, 17, 18-3H] F-244 isolated had a specific activity of 1.3 x 106 DPM/mg. This tritiated F-244 was then used as an affinity.label for HMG-CoA synthase. Attempts to isolate the enzyme-inhibitor complex were unsuccessful due to the low level of radioactivity associated with the tritiated F-244. HMG-CoA synthase was also shown to be inhibited in a time-dependent irreversible manner by {±)-(3-butyrolactone (2). The rate of inactivation (~) was found to be 0.4697 s-1 and the inhibition constant (K1) was found to be 9 mM. The inactivation was found to be irreversible over several hours. / Thesis / Master of Science (MS)

A study of methods for determining the relative abundances of the chlorine isotopes, and the results of mass spectrometric analyses of several chlorine-containing substances. Small variations are shown to exist in nature between the relative abundances of the chlorine isotopes in halite samples from at least two different localities. Other studies involving chlorine isotopes and their possible fractionation are included. / Thesis / Master of Science (MSc)

Call number: LD2668 .T4 1967 S52 / Master of Science

I have studied the effects of polydispersity in systems of hard-sphere, colloidal PMMA particles with and without short-range attraction. In hard-sphere, colloidal systems, the parameter controlling phase behaviour is Ø , the volume fraction of colloids in the solvent. As Ø increases in polydisperse systems, theory predicts a transition from a single phase fluid to a fluid coexisting with a solid (crystal), to a fluid coexisting with multiple solid phases. By considering a volume fraction series of particles with 12% polydispersity and comparing the results with previous experimental results and predictions of the volume fractions within the coexistence regions, we concluded that this system may be exhibiting both fluid-solid and fluid-solid-solid behaviour within the experimental coexistence region. Theory also predicts that coexisting phases in polydisperse hard-sphere systems will fractionate: they will contain different particle size distributions (psds). This was investigated by directly measuring psds for one sample within the coexistence region at different time points. The results show that no statistically significant size fractionation was present after 28 days but by 120 days the solid phase contained a slightly narrower distribution of larger particles than the coexisting fluid phase. At higher than the coexistence region in this polydisperse system, the expected coexisting solids are not observed. Instead, a novel, non-equilibrium phase is present. The dynamics were probed using 3-dimensional dynamic light scattering, which confirmed the non-equilibrium nature of the phase: significant dynamical heterogeneities and anomalous ageing behaviour were present. These experimental dynamics are compared with dynamics obtained from simulations of different hard-sphere psds, including the experimental particle size distribution. The effect of adding a short-range, depletion attraction to a polydisperse colloidal system was systematically explored. Phase boundaries and the position of the metastable gas-liquid binodal were determined experimentally. The resultant phase diagram topology is qualitatively different to a system of monodisperse particles with the same attraction range. Furthermore, within the metastable binodal region, three-phase gas-liquid-solid samples were observed, which is neither an equilibrium or metastable state in monodisperse systems. The coexisting samples were again characterised using electron microscopy and also small-angle x-ray scattering, which revealed significant size fractionation in the gas-liquid separated samples but not in the samples which eventually crystallised.

No description available.

Distributions of water transit times (TTDs), and related storage-selection (SAS) distributions, are spatially integrated metrics of hydrological transport within landscapes. Recent works confirm that the form of TTDs and SAS distributions should be considered time variant-possibly depending, in predictable ways, on the dynamic storage of water within the landscape. We report on a 28 day periodic-steady-state-tracer experiment performed on a model hillslope contained within a 1 m3 sloping lysimeter. Using experimental data, we calibrate physically based, spatially distributed flow and transport models, and use the calibrated models to generate time-variable SAS distributions, which are subsequently compared to those directly observed from the actual experiment. The objective is to use the spatially distributed estimates of storage and flux from the model to characterize how temporal variation in water storage influences temporal variation in flow path configurations, and resulting SAS distributions. The simulated SAS distributions mimicked well the shape of observed distributions, once the model domain reflected the spatial heterogeneity of the lysimeter soil. The spatially distributed flux vectors illustrate how the magnitude and directionality of water flux changes as the water table surface rises and falls, yielding greater contributions of younger water when the water table surface rises nearer to the soil surface. The illustrated mechanism is compliant with conclusions drawn from other recent studies and supports the notion of an inverse-storage effect, whereby the probability of younger water exiting the system increases with storage. This mechanism may be prevalent in hillslopes and headwater catchments where discharge dynamics are controlled by vertical fluctuations in the water table surface of an unconfined aquifer. Plain Language Summary Volumes of water reside within landscapes for varying amounts of time before they are discharged to a stream. That length of time determines how long the water has to interact chemically with soil and rock, and therefore influences the chemistry of water that ends up in stream channels. Quantifying the full range and variability of those travel times remains a challenge. We built an experimental hillslope, which allows us to keep track of all the water that enters and exits the soilsomething that is difficult to accomplish in open environmental systems. We introduced chemically distinct water into the hillslope at specific points in time and followed the movement of that water within, and upon exit from the soil. We discovered that the water being discharged from the hillslope tends to have resided in the landscape for shorter lengths of time when the hillslope is very wet (like a wetted sponge) than when it is very dry (like a dry sponge). This insight helps us understand how different rainfall regimes, and the associated wetness of the landscape, can potentially influence water transit times through the landscape, and their relationship with stream chemistry.

The evolution of plant genomes is notable for manifesting a cycle of whole genome doubling, fractionation (gradual loss of redundant genes) and speciation. The thesis is based on a branching process model of the doubling and fractionation process, integrated with a standard model of sequence divergence. The immediate application of this work is to account for the distribution of sequence similarity for duplicate gene pairs, both within plant genomes and between two related plant genomes in terms of a cycle of polyploidization, fractionation and speciation. We derive a mixture distribution for duplicate gene pair similarities generated by speciation and/or repeated episodes of polyploidization. We account not only for the timing of these events in terms of local modes or peaks of the component distributions, but also their volume, or amplitude, and variance. We outline how to infer the parameters of the model. We illustrate with analyses of the distribution of homolog similarities in a number of plant families: Brassicaceae, Solanaceae and Malvaceae. To our knowledge, this is the first method to account for the volume of the component normals of a distribution of similarities, preliminary to an evolutionarily meaningful inference procedure. In addition, we solve the problem of identifying the ploidy level of a series of two or three polyploidizations by invoking the observed and predicted gene triple profiles for each model, i.e., by calculating the probability of the four types of triple with origins in one or the other event, or both.

Surface water reservoirs in rural areas of the Canadian prairies often have poor water quality due to contamination by dissolved organic carbon (DOC). DOC can activate growth of microorganisms in water distribution systems and form disinfection by-products (DBPs) in water treatment. The presence of microbiological contaminants and DBPs are potentially harmful to human health. Therefore, rapid and simple methods for DOC characterization are needed to evaluate potential water sources and to assist in understanding how best to remove DOC. The first objective of this project was to develop a sample preparation and analysis procedure utilizing Fourier Transform Infrared Spectroscopy (FTIR) to characterize the DOC content of water samples. The second objective was to compare FTIR analysis results for fractionated and un-fractionated water samples to more convention DOC characterization methods (such as UV, SUVA and specific THMFP). The third objective was to demonstrate the application of the procedure to source water assessment and water treatment process evaluation by characterizing the DOC content of several typical treated and un-treated prairie water samples at several locations in Saskatchewan.<p> In the first phase of the study prepared samples of known DOC concentration were separated into six fractions (hydrophobic acid (HPOA), hydrophobic neutral (HPON) and hydrophobic base (HPOB); and hydrophilic acid (HPIA), hydrophilic neutral (HPIN) and hydrophilic base (HPIB)) using resin fractionation techniques. FTIR and conventional UV spectroscopic measurements, DOC concentration, and trihalomethane formation potential (THMFP) measurements were taken on the un-fractionated samples and their fractions. A water matrix interference problem in the FTIR measurements was overcome by depositing a residue of dry solids from the aqueous solution containing the DOC on a flat, organic compound free and non-infrared absorptive gold plated slide before analysis. This simple evaporation procedure developed for concentrating water samples successfully deposited a solid residue for FTIR scanning. Scanning of the solid residue of each sample at multiple locations successfully produced a spectrum of average results suitable for interpretation.<p> Each organic fraction separated from the prepared samples of known DOC was then assessed using FTIR analysis. Comparison of the spectra from the resin adsorption fractions gave an indication of the relationship between functional groups and the hydrophobic/hydrophilic nature of the DOC. The results suggest that the hydrophobic fractions contain more aromatic functional groups. This demonstrates that the FTIR spectra can provide information regarding the hydrophobic/hydrophilic nature of the DOC as an alternative to the resin separation procedure. The sample preparation and FTIR analysis procedure was then used to characterize the DOC content of source and treated waters at several locations within Saskatchewan. The results of these initial investigations indicate the method can effectively identify the major organic functional groups present in source waters and the changes in the major functional groups that occur as the water is subjected to water treatment unit operations and processes. Further, the presence of several key functional groups is related to an increase in THMFP.