The kinetic mechanism of the cAMP-dependent protein kinase has been determined to be random in the direction of MgADP phosphorylation by using initial velocity studies in the absence and presence of the product, phospho-Serpeptide (Leu-Arg-Arg-Ala-Ser[P]-Leu-Gly) , and dead-end inhibitors. In contrast to the kinetic parameters obtained in the direction of Serpeptide phosphorylation, the only kinetic parameters affected by Mg^2+ are the dissociation constants for E:phospho-Serpeptide and E:MgADP, which are decreased by about 4-fold. The dead-end analog MgAMPCP binds with an affinity equal to that of MgADP in contrast to MgAMPPCP, which binds weaker than MgATP. The ratio of the maximum velocities in the forward and reverse reactions is about 200, and the Haldane relationship gives a K-eq of (7.2 ± 2) x 10^2. The latter can be compared to the K-eq obtained by direct measurement of reactant concentrations (2.2 ± 0.4) x 10^3 and 31-P NMR (1 ± 0.5) x 10^3. Data for the pH dependence of kinetic parameters and inhibitor dissociation constants for the cAMP dependent protein kinase are consistent with a mechanism in which reactants selectively bind to an enzyme with the catalytic base unprotonated and an enzyme group required protonated for Ser-peptide binding. Preferentially MgATP binds fully ionized and requires an enzyme residue (probably lysine) to be protonated. The maximum velocity and V/K-MgATP are pH independent. The V/K for Serpeptide is bell-shaped with estimated pK values of 6.2 and 8.5. The dependence of 1/K-i for Leu-Arg-Arg-Ala-Ala-Leu-Gly is also bell-shaped, giving pK values identical with those obtained for V/K-Serpeptide, while the K-i for MgAMPPCP increases from a constant value of 650 μM above pH 8 to a constant value of 4 mM below pH 5.5. The K-i for uncomplexed Mg^2+ obtained from the Mg^2+ dependence of V and V/K-MgATP is apparently pH independent.

Nanoparticles (NPs) are the basis of nanotechnology and finding numerous applications in various fields such as health, electronics, environment, personal care products, transportation, and catalysis. To fulfill these functions, the nanoparticles must be synthesized, passivated to control their chemical reactivity, stabilized against aggregation and functionalized to achieve specific performances. The chemistry of metal nanoparticles especially that of noble metals (Gold, Platinum…) is a growing field. The nanoparticles have indeed different properties from those of the corresponding bulk material. These properties are largely influenced by several parameters; the most important are the size, shape, and the local environment of the nanoparticles. One of the most common synthetic methods for the preparation of gold nanoparticles (AuNPs) is based on stabilization by citrate. Since it was reported first by Turkevich et al. in 1951, this synthetic scheme has been widely used, studied and a substantial amount of important information regarding this system has been reported in the literature. The most popular method developed by Frens for controlling the size of the noble gold nanoparticles based on citrate was achieved by varying the concentration of sodium citrate. Despite a large number of investigations focused on utilizing Cit-AuNPs, the structural details of citrate anions adsorbed on the AuNP surface are still unknown. It is known only that citrate anions “coordinate” to the metal surface by inner sphere complexation of the carboxylate groups and there are trace amounts of AuCl4−, Cl−, and OH− on the metal surface. Moreover, it is generally accepted that the ligand shell morphology of Au nanoparticles can be partly responsible for important properties such as oxidation of carbon monoxide. The use of Au-NPs in heterogeneous catalysis started mostly with Haruta who discovered the effect of particle size on the activity for carbon monoxide oxidation at low temperature. The structure of the citrate layer on the AuNP surface may be a key factor in gaining a more detailed understanding of nanoparticle formation and stabilization. This can be affecting the catalytic activity. These thoughts invited us to systematically examine the role of sodium citrate as a stabilizer of gold nanoparticles, which is the main theme of this thesis. This research is focused on three main objectives, controlling the size of the gold nanoparticles based on citrate (and other carboxylate ligands Trisodium citrate dihydrate, Isocitric Acid, Citric acid, Trimesic acid, Succinic Acid, Phthalic acid, Disodium glutarate, Tartaric Acid, Sodium acetate, Acetic Acid and Formic Acid by varying the concentration of Gold/sodium citrate, investigating the interaction of the citrate layer on the AuNP surface, and testing the activity of the Au/TiO2 catalysts for the oxidation of carbon monoxide. This thesis will be divided into five chapters. In Chapter 1, a general literature study on the various applications and methods of synthesis of Au nanoparticles is described. Then we present the main synthetic pathways of Au nanoparticles we selected. A part of the bibliographic study was given to the use of Au nanoparticles in catalysis. In Chapter 2, we give a brief description of the different experimental procedures and characterization techniques utilized over the course of the present work. The study of the size control and the interaction between gold nanoparticles and the stabilizer (carboxylate groups) was achieved by using various characterization techniques such as UV-visible spectroscopy, Transmission Electron Microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Nuclear Magnetic resonance spectroscopy (NMR) and Fourier transform infrared spectroscopy (FTIR). In Chapter 3, we discuss the synthesis and size control of Au nanoparticles by following the growth of these nanoparticles by UV-Visible spectroscopy and TEM. We then describe the effect of the concentrations and of various type of the stabilizer, and the post-synthesis treatment on gold nanoparticles size. In Chapter 4, we focus on determining the nature of the interactions at molecular level between citrate (and other carboxylate-containing ligands) and AuNP in terms of the mode of coordination at the surface, and the formal oxidation state of Au when interacting with these negatively charged carboxylate ligands (i.e., LX- in the Green formalism). We achieve this by combining very advanced 13C CP/MAS, 23Na MAS and low-temperature SSNMR, high-resolution transmission electron microscopy (HRTEM) and density functional theory (DFT) calculations. A particular emphasis will be based on SS-NMR. In Chapter 5, we study the influence of pretreatment of 1% Au/TiO2 catalysts on the resulting activity in the oxidation of carbon monoxide, the effect of the concentration and the type of the ligands on the catalytic activity. The catalysts were characterized by TPO, XRD, and TEM spectroscopy.

PrnB is a heme-containing enzyme, which catalyzes the ring rearrangement reaction of 7-chlorotryptophan to produce 3-(3-Chloro-2-nitrophenyl)pyrrole. This thesis describes the initial isolation and characterization of PrnB, the second enzyme associated with the pyrrolnitrin biosynthetic pathway in Burkholderia ambifaria. Additionally, alternative peroxidase reactivity was used to study how amino-acids bind to the substrate binding pocket of PrnB. The peroxidase activity of PrnB was measured using three different peroxidase activity assays at various pH values. The peroxidase data was compared to similar studies with the classic peroxidase, Horseradish peroxidase (HRP). Generally, PrnB showed weak peroxidase reactivity. However this weak reactivity was an experimental handhold, where tryptophan and other substrate binding events can be explored using classic inhibition steady-state kinetics. The rate of 2-aminophenol oxidation by PrnB was used as a model assay to monitor how molecules such as L-tryptophan, L-alanine, indole, L-phenylalanine, and L-tyrosine interact with the PrnB active site.

Pollution from hydrofluorocarbons (HFC) poses a serious challenge to the environmental community. Released from industrial operations, they have contaminated both the atmosphere and groundwater and are considered persistent in both media.1 For over the past 20 years, the practice of synthesizing hydrofluorocarbons as alternatives to chlorofluorocarbons (CFC) has been conducted in an effort to reverse the effects of stratospheric ozone layer depletion. 2,3 However, in doing so these new fluorinated compounds exhibited an unexpected property as a potent global warming greenhouse gas (GHG) with radiative forcing potentials in the range of 100 to 10,000 equivalents greater than carbon dioxide.4 Conversely, HFCs exhibit desirable properties as precision cleaning solvents due to their low surface energy but that use has lead to releases contaminating groundwater resulting in recalcitrant pollution in the form of dense nonaqueous phase liquids (DNAPL).5 The Environmental Protection Agency (EPA) has recently requested studies on the environmental impact of HFCs with respect to a number of petitions received from various environmental action groups imploring the use of the Montreal Protocol as the vehicle by which to achieve elimination of the compounds from industrial operations.6,7 Additionally, results from studies requested by the international community have shown HFCs to exhibit developmental and neurological damage in animal life along with their impact to humans remaining not completely understood.8,9,10 Therefore, the potential hazards of HFCs to human health and the environment necessitates the development of an effective and environmentally responsible technology for their remediation from groundwater. The National Aeronautics and Space Administration (NASA) has employed the use of various halogenated solvents in its spacecraft cleaning operations at its facilities for many years iv and in that time experienced accidental releases which eventually resulted in environmental contamination.11,12,13 Many of the organic solvents employed in these operations consisted of halogenated compounds with most being partially chlorinated and fluorinated hydrocarbons. Through normal use and operation, releases of these materials found their way into the environs of atmosphere, soil and groundwater. Remediation of fluorinated compounds has not followed the successful path laid by clean-up technologies developed for their chlorinated counterparts.14,15,16,17 Fluorinated compounds are resistant however to those methods due to their unreactive nature stemming from the properties of the strong carbon-fluorine bond. 18 This unique bonding property also ensures that their environmental persistence endures. 19 One particular fluorinated groundwater contaminant, the HFC 1,1,1,2,2,3,4,5,5,5-decafluoropentane (DFP), which serves as an excellent cleaning agent and has been used by NASA since the late 1990’s and still remains in use today, was selected as the focus of this study. 20 For this study, various reductive metal systems were evaluated for their capability towards effective degradation of DFP. These included the metals: iron, magnesium, aluminum and zinc and several bimetallic alloys as well as attempts employing some on carbon support. Variations in protic solvent reaction media and acidic metal activation were also explored. The bimetallic reductive catalytic alloy, magnesium with palladium on carbon support Mg(Pd/C) in aqueous media, proved to be the successful candidate with 100% conversion to simple hydrocarbons. Mechanistic evaluation for degradation is proposed via a series of stepwise catalytic reduction reactions. Kinetic studies revealed degradation to obey second order reaction kinetics. Further study should be conducted optimizing an in situ groundwater delivery method for field application. Additionally, the developed technology should be assessed against other v groundwater fluorocarbon pollutants; either as a method for remediating multiple fluorinated polluted sites or as a polishing agent where all other non-fluorinated halogen pollutants have been abated.

<p> The catalytic asymmetric transformation of carbonyl compounds via iminium and enamine intermediates using chiral amines as organocatalyst has grown remarkably over last decade. Various "metal-free" reactions including aldol, Mannich, Michael, alkylation and Knoevenagel types have now been reported efficiently using simple amino acids as the sole organocatalysts. Amongst these, proline has proven to be particularly useful as a general catalyst in such catalytic asymmetric syntheses due to its unique properties. Nonetheless, proline suffers inherent fundamental disadvantages as an organocatalyst in terms of its solubility in organic media, limiting reactions to polar aprotic solvents such as DMF or DMSO. We have been interested in the synthesis of derivatives of proline incorporating functional groups that would render the chiral secondary amine fully soluble in organic solvents such as THF or dichloromethane and others that could be employed in aqueous media. The synthesis of these catalysts and their application towards the asymmetric synthesis will be presented.</p> <p> The thesis also describes isolation and identification of natural products and synthesis of their semi-stabilised derivatives. Sakuranetin and dihydrowagonine were isolated from Prunus avium plant parts, menisadurilide was isolated from Dicentra spectabilis extracts while narciclasine was isolated from Narcissus pseudonarcissus plant parts. Semi-synthetic derivative, trans-dihydronarciclasine was prepared from natural product narciclasine. Both the derivatives were subjected to antifungal and human cytochrome inhibition activity and their correlation is explained. The Amaryllidaceae family alkaloids and their semi-synthetic derivatives were subjected to biological testing and an important structural property is correlated to their activities.</p> / Thesis / Master of Science (MSc)

<p> The optimal temperature policy with time is sought which maximizes the total amount of reaction in a fixed time in a tubular reactor with uniform temperature and decaying catalyst for a single reversible reaction.</p> <p> A numerical procedure together with theoretical developments is used to solve this problem for two kinetic models. The problem is treated in the format of Pontryagin's Maximum Principle.</p> <p> Computer listings are given in the Appendix for the following cases A) Optimal policy for irreversible reactions 8) Optimal policy for isothermal irreversible reactions C) Optimal policy for reversible reactions.</p> / Thesis / Master of Engineering (MEngr)

Biodiesel is one of the most widely used biofuels in the world, due in part to its simplicity of production, compatibility with existing engines, and reduction of green house gas emissions. However, technical difficulties with biodiesel include: (1) the need of highly refined oil for ASTM compliance, (2) incompatibility with the petroleum-diesel pipeline distribution system, and (3) a relatively small inventory of expensive feedstocks. Issues (1) and (2) could be overcome by the production of biofuels using chemical processes associated with petroleum refining. Catalytic lipid cracking could result in green diesel, a fuel chemically similar to conventional diesel but derived from a clean renewable feedstock. The impact of phosphorus poisoning on catalytic cracking of lipids has been studied in this work using both homogeneous and heterogeneous catalysts. Catalytic cracking of model lipids was shown to occur in a homogeneous liquid phase with triflic acid, a superacid 100 times more acidic than sulfuric acid. Products obtained from the reaction were heavily oxygenated and generally unsuitable for fuel use, suggesting the need for heterogeneous catalytic cracking. Reaction kinetics show a high linear dependence on Brönsted system acidity, with an overall reaction order of 3. The affect of phosphorus on heterogeneous acid cracking was then studied. Since lipid feedstocks contain small amounts of phospholipids knowledge of the interactions between phospholipids and zeolites is crucial to a system-wide understanding of the lipid cracking process. Phosphorus-containing compounds were used to poison ZSM-5 (a solid zeolite catalyst) in order to simulate the cracking of phospholipids. Model compounds were then cracked over the poisoned zeolite, with differences in product distribution and kinetics based on phosphorus loading recorded. It was shown that phosphorous has a dramatic effect on both conversion and product distribution of cracking reactions. It is believed that phosphorous binds irreversibly to heterogeneous active sites, causing the majority of deactivation. To address the issue of limited feedstock availability, research was also undertaken to find new lipids sources for biofuel use. It was determined that lipids extracted from microorganisms grown in a municipal wastewater treatment system could be suitable. However, any phosphorous must be removed before catalytic cracking of the extracted lipids.

No description available.

<p> The two carboxyvinyl transferases MurA and AroA are essential for bacterial survival, and are proven or potential antibiotic targets. The reactions they catalyze are chemically challenging, involving protonation of an ethylene group in the first step, and deprotonation of a methyl in the second step. In order to probe how the enzymes promote these reactions, the reverse reactions from enolpyruvyl compounds (EP-OR) plus phosphate to phosphoenolpyruvate (PEP) plus R-OH were investigated, and compared with EP-OR hydrolysis reactions catalyzed by phosphate analogues. </p> <p> Thirteen phosphate analogues were used to study EP-OR hydrolysis. Among these phosphate analogues, many could bind to the free enzymes, but only three could promote hydrolysis. The products were pyruvate and the corresponding alcohol (S3P in AroA/EPSP reaction and UDP-GicNAc in MurA/EP-UDP-GicNAc reaction). The most effective analogue was arsenate. The mechanism of the arsenate-promoted reaction was examined in detail. The hydrolysis reaction proceeded though an arseno-tetrahedral intermediate with AroA, a similar reaction pathway to the natural reaction. This arseno-tetrahedral intermediate was converted to arsenoenolpyruvate and hydrolyzed spontaneously. MurA also likely catalyzed arseno-tetrahedral intermediate formation, and appeared to catalyze arsenoenolpyruvate breakdown, though it is possible that it was a bystander in the reaction, with the tetrahedral intermediate being formed by water attack on C2 of EP-UDP-GicNAc. There was a fast solvent exchange step before EP OR was converted to arseno-THI by AroA or MurA. This strongly indicated an oxacarbenium ion like intermediate before the arseno-tetrahedral intermediate. </p> <p> The catalytic machinery for stabilizing such an unstable oxacarbenium ion like intermediate was investigated by studying ligand binding. Based on information from all the phosphate analogues, there were evidence that the enzyme undergoes an conformational change upon binding with phosphate, by which EPSP was distorted into an oxacarbenium ion like intermediate. </p> / Thesis / Master of Science (MSc)

Since careful consideration must be given to the catalyst used in catalytic cracking operation in the petroleum industry to assure economic operation, laboratory catalyst activity test units have been developed. These units approximate the conditions in large scale commercial cracking units. It was the purpose of this investigation to determine the amount of cracking that was obtained from catalytic effects in cracking a standard light East Texas gas oil over a Houdry pellet catalyst when compared to the cracking over silica at temperatures from 500 to 1200 °F in a catalyst activity test unit. A catalyst activity test unit was used to determine the percentage conversion of the feed oil to lower molecular weight hydro-carbons using a Houdry pellet catalyst in one series of tests and silica, which is regarded to be noncatalytic, in another series. Fifteen determinations were made at various temperatures from 580 to 1190 °F and a space velocity of 1.0 volume of feed per volume of catalyst per hour. Ten determinations were made at a space velocity of 2.0 volumes of feed per volume of catalyst per hour at temperatures from 595 to 1160 °F. Data were collected on the quantity of liquid and gaseous products produced, as well as the operating conditions employed. After each cracking determination, the packing was regenerated by heating in the presence of air to burn off any carbonaceous deposits. At a space velocity of 1.0. and various temperatures ranging from 580 to 1190 °F the use of Houdry pellet catalyst produced more cracking than silica at like temperatures. The use of the catalyst effectively reduced the temperatures of the cracking reactions approximately 300 °F at a space velocity of 1.0. The effect of the catalyst was lessened by the effect of temperature at approximately 1200 °F and a space velocity of 1.0. When cracking over silica changing the space velocity from 1.0 to 2.0 raised the temperature required 50 °F for a given amount of cracking. / Master of Science