Dimethylacetamide (DMA) solvent is oxidized catalytically to CH₃CON(CH₃)CH₂OOH and CH₃CON(CH₃)CHO under H₂/0₂ mixtures at 50°C in the presence of the dimethylsulfoxide complex RhCl₃(DMSO)₃ (I) at a rate which is much faster than peroxide-initiated autoxidation of DMA under O₂ alone. The hydroperoxide is thought to be the initial product, and the N-formyl derivative its decomposition product. An accompanying metal-catalyzed hydrogenolysis of 0₂ leads to H₂0₂ and H₂0. Hydrogen peroxide and CH₃CON(CH₃)CH₂OOH are the only products formed in the early stages of the catalytic reaction. The maximum rate of gas uptake in this initial region is independent of the partial pressure of 0₂, but shows linear dependences on Rh and H₂. Stoichiometry, rate and spectral data are consistent with an initiation reaction between complex I and H₂, and then 0₂ to give a catalytically active RhIII (0₂=) (DMA) species (II) (eq. 1) [formula omitted] The autoxidation of DMA and the hydrogenolysis of 0₂ are postulated to occur via independent pathways involving II (eqs. 2 and 3). [formula omitted] In the absence of H2, II degenerates to catalytically inactive species. The role of H₂ in the DMA autoxidation is thought to be the regeneration of Rh I species and hence II, from deactivated forms of II. Eventual slow, irreversible deactivation of the catalyst and the probable participation of the H₂0₂ product in peroxide initiated free-radical autoxidations complicate the interpretation of later stages of reaction. Diphenylsulfide (DPS) is catalytically oxidized to the sulfoxide by complex I under H₂/O₂ in DMA at 50°C, but accompanying oxidation of the solvent persists even in the presence of a 100-fold excess of DPS over Rh. Oxidation of the sulfide is thought to involve H₂0₂ liberated in the catalytic hydrogenolysis of 0₂. Complex I in CH₂C1₂ or C₂H₄CL₂ reacts with CO to give the dimethylsulfide complex RhCL₃(DMS)₃ via a facile reduction of DMSO ligands. Dimethylsulfoxide is reduced also by RhI species in CH₂CL₂ in the presence of two equivalents of acid to yield DMS, RhIII and H₂0. However, Rh I /2H⁺/DMS0 systems are relatively stable in DMA, because of the proton affinity of the solvent. Complex I reacts also with the strongly basic tertiary amine NEt₃ via a redox process in which the RhIII is reduced to Rh I with an accompanying dehydrogenation of the amine (eq. 4). RhCl₃ + 3NEt₃ → RhCl + 2NEt₃ HCl + CH₂=CHNEt₂ (4) The resulting ethenamine then reacts with I to give the ƞ¹-ylidic complex, RhCl₃(DMS̠O)₂(⁻CH₂CH=⁺NEt₂). Data from an earlier thesis, on a reaction between complex I and 1,8-bis(dimethylamino)naphthalene (or Proton Sponge), are reinterpreted in terms of a similar redox reaction that gives an N-carbene fragment (eq. 5),which is stabilized within the RhIII complex, RhCl₃(DMS̠O)₂(=CH-N(Me)-C₁₀H₆NMe₂•HCl). [formula omitted] / Science, Faculty of / Chemistry, Department of / Graduate

A spectroscopic and enzymatic investigation of the cytochromes of B. megaterium and B. subtilis was conducted. Attempts were made to isolate and characterize the individual cytochromes as well as to determine the locale of such activities as cytochrome c oxidase, DPNH oxidase, succinic dehydrogenase, cytochrome c reductase and diaphorse. Only two methods proved effective in liberating the cytochromes; disruption of the cells with sonic osillations and grinding tlhe cells with alumina. These procedures caused a fragmentation of the cell membrane. It was found that the entire cytochrome complement of these two bacteria was bound intimately to particles which most likely arise from the cell membrane. The spectrum of these cytochrome containing particles displayed the typical four banded spectrum found in mammalian tissues and yeast. From the various studies made, the presence of cytochromes of the a, b, and c type was confirmed. A concentration of the cytochrome bearing particles could be brought about by either an ammonium sulfate fractionation or by centrifugation at 144,000 x g. for three hours. When the particles were centrifuged, a concentration of these particles in an intense color layer at the bottom of the centrifuge tube resulted. The spectrum of this concentrate showed peaks which were several times more intense than were those shown by the original sonic extract. With these sharpened peaks it was easier to note changes in cytochrome composition of different batches of cells. A few batches of cells contained a high content of cytochrome c, while most batches of cells had only a low content of this particular cytochrome. The content of the a type cytochrome also varied markedly in the different batches of cells. The content of cytochrome b was more resistant to change, but even the amount of this cytochrome showed some variation. A procedure for obtaining a partially purified cytochrome c from the cytochrome concentrate is presented. Extraction was brought about by pre-treating the fraction with Triton X-100 before performing a digestion with the hydrolytic enzyme lipase. This treatment liberates a soluble cytochrome c which can be precipitated from a concentrated ammonium sulfate solution with trichloroacetic acid in the usual manner. The absorption maxima of the reduced spectrum of the partially purified cytochrome were at 550, 520, and 415 mμ. The Soret peak shifted to 408 mμ. when the pigment was oxidized. A short discussion of the similarities between this bacterial cytochrome c and a lipid soluble cytochrome c obtained from mammalian tissues is included. The enzymatic studies showed that cytochrome c oxidase, DPHN oxidase, and succinic dehydrogenase are associated witht he particle described above, while the diaphorase and cytochrome c reductase were found in the more soluble fractions. Inhibition studies with cytochrome c oxidase, using cyanide, carbon monoxide and azide revealed a similar inhibition pattern to that shown by mammalian cytochrom oxidase.

Dissertation (Ph.D.)--Auburn University, 2006. / Abstract. Vita. Includes bibliographic references.

Ph.D. / The aim of this study was the development of a new technology for the manufacturing of amorphous silicon (a-Si:H) solar cells on flexible substrates. Kapton R , a commercially available polymer, was used as a substrate to this end. The use of such a polymer, as opposed to glass, results in dramatic savings and also affords the possibility for technological innovation. From the start the project was planned to develop and commission a medium-scale pilot plant manufacturing process. The project thus consisted of two sections: the design, fabrication and implementation of a large-area deposition system, as well as research and development of the materials and cells. A pilot plant was developed and successfully implemented. The optimization of the reactor resulted in very homogeneous materials with good electrical- and optical characteristics. The individual materials were optimized and incorporated into the standard cell configuration (on glass). This process was then transferred to kapton and the configuration was optimized. The use of kapton, as opposed to glass, implies the growth of silicon on a metal film on the kapton. This process leads to a number of phenomena occurring in cells on kapton which do not occur in standard cells on glass. The phenomena include the crystallization of a-Si:H at low temperatures, degradation of the material properties and unwanted microstructure. The origin of these phenomena can be linked to the high occurence of metal/Si-interdiffusion. It was found that this inter-diffusion can be decreased by the insert i on of a thin ZnO buffer layer between the back metal contact and the a-Si:H. The flexible cells were successfully developed and optimized for large areas. An operational manufacturing process was thus developed and the product of this study can now be applied successfully in practical applications.

Serine proteases are a family of enzymes with a wide array of functions across both eukaryotes and prokaryotes. Here we have attempted to produce the serine proteases rat mast cell protease 2 and mouse mast cell protease 5 in a culture of HEK 293 cells; and mouse mast cell protease 4, platypus granzyme B-like protease and platypus hypothetical protease in a baculovirus expression system. Following production we wanted to analyse these serine proteases using a phage display assay and a battery of chromogenic substrates.

Thesis (Ph.D. (Biochemistry, Microbiology & Biotechnology)) - Rhodes University, 2008.

>Magister Scientiae - MSc / Unavailability and contamination of available water resources are major factors contributing to adverse health conditions worldwide. AgNPs present a potential strategy for water purification; however, their ability to accumulate in organs such as the kidneys, lungs and spleen is a possible source of toxicity. This study investigates the toxicity of AgNPs to Saccharomyces cerevisiae (S. cerevisiae). S. cerevisiae is an excellent model organism for assessing toxic compounds that affect eukaryotic organisms due to their ease of cultivation. AgNPs were prepared by photo-reduction of silver nitrate with OSRAM Vitalux lamp (300 W and 230 V) in the presence of stabilizing agents such as polyvinylpyrrolidone and citric acid, yielding AgNPs. The effects of varying the concentration of the stabilizing agent, time of exposure to the light source, and pH were investigated. The formation of AgNPs was analysed by ultra-violet spectroscopy (UV-Vis) and transmission electron microscope techniques. The results showed that the AgNPs absorbed ultra-violet radiation between 400 and 500 nm and TEM images showed the particles to be both spherical and needle-like in shape. The shapes of the AgNPs were largely dependent on the synthesis method applied. The toxicity of AgNPs was assessed using metabolic activity of yeast cells as biomarker andmonitored with of the chromogenic assay, XTT. S. cerevisiae was introduced into different concentrations of AgNPs and incubated at 37oC for 72 h. After the incubation, XTT assay was performed to assess the cell viability. The XTT results showed that high concentration of AgNPs (100 µg/mL) inhibited the growth of S. cerevisiae. The synthesis of AgNPs and theassessment of their toxicity on S. cerevisiae was thus undertaken and established in this work.

A disponibilidade de hemoderivados é um parâmetro importante para medir a qualidade da saúde em um país. Dentre os produtos hemoderivados, imunoglobulinas tem alto valor agregado. O Instituto Butantan tem por objetivo o estabelecimento de uma planta industrial para fracionamento de plasma, com um processo produtivo baseado principalmente em cromatografias. Eventos tromboembólicos a partir de infusões de imunoglobulinas por via intravenosa (IgIV) foram relacionados com presença de Fator XI de coagulação (FXI) como contaminantes nas preparações de IgIVs. Com objetivo de detectar o FXI nas frações, o processo cromatográfico foi testado em escala piloto, bancada, e em cromatografia direta e o FXI foi dosado nas frações iniciais e no produto final IgIV. Foram estabelecidos os métodos de dosagem de atividade de FXI por tempo de coagulação e ensaio cromogênico. Concluímos que o FXI acompanha a IgG nas etapas iniciais dos processos cromatográficos e verificamos que ocorre a presença de FXI nos produtos finais. Este trabalho contribui para o desenvolvimento do conjunto de testes de controle de qualidade de biofármacos derivados de plasma humano. / The availability of hemoderivatives is an important parameter to measure a countrys health quality. Among hemoderivatives products, immunoglobulin have high value.. Instituto Butantan, aims the establishment of an industrial plant for plasma fractionation with a process drawn, based mainly in chromatographies. Thromboembolic events from infusions of intravenous immunoglobulins (IVIg) have been related with the presence of coagulation Factor XI (FXI) as contaminant in the IVIG preparations. With an objective of tracking FXI in the chromatographic fractions, the process was tested in pilot and bench scales and in direct chromatography and the FXI was measured in the initial fractions and in the final product IVIg. The methods of measurement of FXI activity thru coagulation time and chromogenic assay were established. We have concluded that FXI accompanies IgG in the early stages of the chromatographic processes and verified that the presence occurs in the final products, This work contributes to the development of the set of quality control tests of biopharmaceuticals derivatives from human plasma.

This thesis presents thermodynamic studies performed by electrochemical methods (cyclic voltammetry, electrochemical impedance and chronopotenciometry) in three of the most important electrochromic materials: a-WO3, conducting polymers and viologens. Electrochromic materials are very promising as a low-consuming technology. By incorporating these materials in windows of buildings or vehicles, approximately a 30% of the consumed energy in these systems can be saved.Regarding the a-WO3, apart from other contributions, a new model based on lattice distortions, able to explain the intercalation thermodynamic in this material, is proposed. In the conducting polymers field, a Gaussian energy distribution is proved to account for the initial part of the so broad oxidation peaks observed in cyclic voltammetry. Finally, the coloration kinetics of the viologen modified n-TiO2 electrode is explained.

The chromogenic properties of tungsten trioxide (WO3) have been studied by photoluminescence spectroscopy at 4.2 K in order to characterize the electronic structure of this material and see how this relates to optical responses during chromogenic coloration. Transition processes between electron energy states are often the cause of optical phenomena and it is important to identify such processes in order to understand the chromogenic coloration of tungsten oxide films. Much research work has been devoted to characterize the physical and chemical mechanisms that are responsible for this coloration and this is of fundamental importance to understand the chromogenic behavior. The latest research shows that oxygen vacancies could play an important role in certain coloration processes, but it is still a matter of debate whether these are important for the overall response. This work aims to identify specific transitions that are related to oxygen vacancies by measuring photoluminescence from films with controlled vacancy content. The main goal of the project was to set up an experiment that could measure photoluminescence at liquid helium temperature. This was done by installing and integrating the components included in this experimental set-up. The films had been prepared prior to this work and were deposited on a nanocrystalline CaF2 substrate, which is a material that has a very large band gap and was therefore expected to fully transparent in the UV range. However it was found that the substrate inelastically scattered the UV excitation light, which produced strong signals that overshadowed the photoluminescence and prevented an effective characterization of the electronic structure in the films. Instead, suggestions were given on how to minimize uncertainty factors and overcome the difficulties met in this work. It was also found that the films attain a lasting blue coloration by exposure to UV light in vacuum, and that this might be due to oxygen being desorbed from the film during experiments in vacuum.