Zugl.: Hohenheim, Univ., Diss., 2008

Zugl.: Hamburg, Univ., Diss., 2008

Universiẗat, Diss., 2000--Kaiserslautern.

Universiẗat, Diss., 2006--Würzburg.

Marburg, Universiẗat, Diss. : 1994.

Techn. Universiẗat, Diss., 2001--Berlin.

Techn. Universiẗat, Diss., 2003--Berlin.

Universiẗat, Diss., 2004--Kiel.

The chemical industry is an essential part of modern society and therefore has a responsibility to develop solutions for the problems facing it. A major problem is continuing to match the material demands of a growing global population whilst simultaneously decreasing the consumption of finite natural resources and limiting the emissions of greenhouse gasses. An optimised catalytic system that shortens, or intensifies, the process chain for the production of chemicals can be an effective solution to this challenge. Auto-tandem catalysis is where a single metal-ligand complex facilitates two or more sequential transformations. For example: alkenes are hydroformylated into aldehydes which are then hydrogenated into alcohols. The alcohols have use as plasticisers or surfactants for metal extraction. A previously reported auto-tandem catalysis system was shown to be capable of sequential hydroformylation-hydrogenation of 1-octene to nonanol. It consisted of the neutral rhodium precursor [Rh(acac)(CO)2] and the bidentate ligand xantphos in 10% iPrOH/H2O co-solvent at temperatures of 160°C. Investigations, reported in this thesis, revealed that xantphos type ligands, with their large bite-angle, and high temperatures are required to generate the hydrogenation activity. However, in contrast to the previous system, water is not necessary; with the same results produced in toluene:iPrOH solutions and water:iPrOH solutions. It is proposed that the iPrOH or H2O has a direct influence in the catalytic cycle, either as a hydrogen-shuttle or generates a cationic rhodium species, known to be active in hydrogenation. High temperature NMR studies show the standard resting state of the hydroformylation catalyst is still predominant at high temperatures therefore the proposed catalytic cycle starts from this step. A recurring problem in the industrial process chain is the separation of the catalyst from the final products. Combing a TiO2 ceramic membrane with a POSS (polyhedral oligomeric silsesquioxane) modified tin catalyst and phosphonium iodide co-catalyst, for the coupling of epoxides and CO2 to make cyclic carbonates, was investigated. The catalyst system showed good substrate compatibility for a range of epoxides. In a prototype membrane set-up the system demonstrated a long catalyst life time, however significant leaching was also observed.

Mycoplasma hyopneumoniae é uma bactéria de tamanho diminuto, caracterizada por um genoma pequeno, com baixo conteúdo GC. Está associada com doenças respiratórias de suínos, resultando em prejuízos produtivos e econômicos na indústria animal. A presença de sequências de DNA repetitivas, que ocorrem em grandes quantidades em células eucarióticas, vem sendo cada vez mais identificadas em genomas de procariotos, sendo também associadas a um potencial papel regulador. Uma vez que a regulação da transcrição nesses organismos ainda é pouco entendida, o objetivo do presente estudo foi realizar uma busca in silico por elementos repetitivos nas regiões intergênicas do genoma de M. hyopneumoniae linhagem 7448. Dois tipos de repetições foram selecionados para a busca inicial: tandem e palindromes. Regiões intergênicas de até 500 pb a montante do sítio de início da tradução de todas as CDSs do genoma de M. hyopneumoniae linhagem 7448 foram utilizadas para a predição. Para cada tipo de elemento dois programas computacionais independentes foram utilizados. As predições in silico resultaram em 144 repetições em tandem e 1.171 palindromes. O DNA repetitivo se encontra distribuído a montante de 86% das unidades transcricionais de M. hyopneumoniae linhagem 7448. Análises comparativas entre genomas de micoplasmas demonstraram diferentes níveis de conservação dos elementos repetitivos entre linhagens patogênicas e não-patogênicas. Linhagens patogênicas revelaram uma conservação de 59%, enquanto que a não patogênica, somente de 46%. Através de ensaios de amplificação quantitativa de DNA, foi observado diferentes níveis de expressão em genes codificantes para importantes proteínas, como glicina hidroximetiltransferase, lipoproteína, adesinas e proteína ligadora de GTP. Os genes codificantes para essas proteínas divergiam no número de repetições palindromes e tandens na sua respectiva região intergênica. Além disso, repetições encontradas em 206 genes já descritos como regulados em diferentes condições em M. hyopneumoniae linhagem 232 mostraram aproximadamente 80% de conservação em relação à linhagem M. hyopneumoniae linhagem 7448. Todos esses resultados sugerem um potencial papel regulador das repetições de DNA em tandem e palindromes em Mycoplasma. / Mycoplasma hyopneumoniae is a diminutive bacterium, characterized by a small genome with a low GC content. It is commonly associated with swine respiratory diseases, resulting in productivity and economic losses in the animal industry. Repetitive DNA, which occurs in large quantities in eukaryotic cells, has been increasingly identified in prokaryotic genomes, and has been associated with a potential regulatory function. Once transcription regulation in these organisms is still poorly understood, the aim of the current study was to perform an in silico search of repeat elements in the genomic intergenic regions of M. hyopneumoniae strain 7448. Two types of repeats were selected for initial search: Tandem and Palindromic. Intergenic regions up to 500 bp upstream from start codon of M. hyopneumoniae strain 7448 CDSs were used as input for the software’s prediction. For each type of repeat sequence, two independent software packages were used. Computational analysis results in 144 tandem repeats and 1,171 palindrome elements. The repeats were distributed in the upstream region of 86% of transcriptional units of M. hyopneumoniae strain 7448. Comparative analysis between distinct mycoplasmas, demonstrate different indices of repeat conservation among pathogenic and non-pathogenic strains. Pathogenic strains revealed 59% conservation, while non-pathogenic only 46%. Through assays of quantitative amplification of DNA, different levels of expression in genes coding important proteins have been demonstrated, as glycine hydroxymethyltransferase, lipoprotein, adhesins and GTP-binding protein. These protein coding genes differ in number of palindromes or tandem repeats in respective upstream regions. In addition, repeats found in 206 genes already described to be regulated in different grow conditions in M. hyopneumoniae strain 232 showed almost 80% of conservation in relation to M. hyopneumoniae strain 7448. All these findings, suggests a potential regulatory role of tandem and palindrome DNA repeats.