Thesis (Ph. D.)--Oregon State University, 2007. / Printout. Includes bibliographical references. Also available on the World Wide Web.

Thesis (M.S.) University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (May 18, 2007) Includes bibliographical references.

Made available in DSpace on 2014-12-02T11:16:39Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-02-24Bitstream added on 2014-12-02T11:21:04Z : No. of bitstreams: 1 000774036_20150224.pdf: 478460 bytes, checksum: 5c3bcdef535ae0c31c4b7881e50abd76 (MD5) Bitstreams deleted on 2015-02-27T13:20:34Z: 000774036_20150224.pdf,Bitstream added on 2015-02-27T13:21:10Z : No. of bitstreams: 1 000774036.pdf: 3030358 bytes, checksum: 222bd63dbd7f35d80957befc6fb96c7e (MD5) / Fungos endofíticos são microrganismos que colonizam assintomaticamente o interior de plantas, sendo encontrados em órgãos vegetais como as folhas, caule, frutos, sementes e raízes, podendo habitar a planta por toda vida, e são transmitidos, em alguns casos, para futuras gerações através da semente do hospedeiro. Estes exibem interações ecológicas especificas em seu habitat que tem sido pouco exploradas como estratégia para a descoberta de novos produtos naturais bioativos. Entre as varias modificações de meios de cultivo para estimular rotas biossintéticas silenciosas e aumentar a produção metabólica, a técnica OSMAC (One Strain Many Compounds) foi empregada neste trabalho. Colletotrichum gloeosporioides isolado de Eugenia jambolana foi cultivado em dois meios de cultivo sólidos (arroz e milho) e cinco líquidos (Czapek, Malte, Nutrient, PDB e YM), na presença e ausência de rede de polietileno como suporte sólido, objetivando avaliar a variação na produção de metabólitos secundários. Com a variação dos meios de cultivo, foi possível observar grande variação metabólica em todos os meios, o que foi constatado pelas analises por RMN de 1H e CLAE/DAD. Para o cultivo em extrato de malte na presença do suporte sólido (rede de polietileno) foi observado um aumento de massa de aproximadamente 275% no cultivo. Os extratos EjC(05)Arroz, EjC(05)YmSR, EjC(05)MaltSR e EjC(05)MaltCR, mostraram potencial antitumoral contra as linhagens OVCAR (carcinoma de ovário), HCT-116 (cólon humano) e SF-295 (glioblastoma humano). Avaliação de todos os extratos brutos permitiu selecionar o extrato EjC(05)MaltCR para a desreplicação das substâncias produzida, sendo possível identificar as dicetopiperazinas Ciclo Prolina-Valina e Ciclo Prolina-Leucina/Isoleucina. / Endophytic fungi are microorganisms that asymptomatically colonize the interior of plants, being found in plant organs such as leaves, stems, fruits, seeds and roots, the plant may dwell for a lifetime, and are transmitted in some cases, for future generations through seed host. These exhibit specific ecological interactions in its habitat that has been little explored as a strategy for the discovery of new bioactive natural products. Among the various modifications of culture media to stimulate and increase silent biosynthetic pathways and metabolic production, OSMAC (One Strain Many Compounds) technique was used in this work. Colletotrichum gloeosporioides isolated from Eugenia jambolana was grown in two different kind of media: two nutrient solids (rice and maize) and five nutrient liquids (Czapek, Malte, Nutrient, PDB and YM) in the presence and absence of polyethylene as a solid support network, to evaluate the variation in the production of secondery metabolites. With the change of the culture media, we observed high metabolic variation in all media, which was corroborated by analysis by 1H NMR and HPLC-DAD. For cultivation in malt extract in the presence of the solid support network (polyethylene) was observed a mass increase of approximately 275% in cultivation. The extracts EjC(05)Arroz, EjC(05)YmSR, EjC(05)MaltSR and EjC(05)MaltCR showed antitumor potential against OVCAR (ovarian carcinoma), HCT -116 (human colon) strains and SF- 295 (human glioblastoma). Evaluation of all crude extracts allowed select the EjC(05)MaltCR for dereplication of substances produced, making it possible to identify the diketopiperazines Cycle Proline-Valine and Cycle Proline-Leucine/Isoleucine.

Bioassays of Flaveria linearis leaf extracts against bacterial phyllosphere isolates, E. coli and B. cereus demonstrated that the isolates were just as susceptible to thiophene phototoxicity as the other bioassay microorganisms. The isolates' lack of resistance suggested that phyllosphere thiophene concentrations were insufficient to generate a phototoxic microenvironment. Bacterial cell wall composition and detoxification mechanisms were important factors in resistance to phototoxicity. Additional pre- and post-infectional defense metabolites with selective phototoxic and antimicrobial properties were also detected in leaf extracts. Furthermore, HPLC analyses identified novel, water-soluble polyacetylenes which were also detected in other Flaveria species. UV spectroscopy and enzyme hydrolysis data permitted partial characterization of two species: i) a galactolipid derivative containing a diene-triyne acetylene and ii) a glucose-containing oligo/polysaccharide with a diene-triyne acetylene. These acetylenes may function as intermediates in thiophene biosynthesis or alternatively may be involved in storage and transportation.

Orientador: Angela Regina Araujo / Banca: Sandra Imaculada Maintinguer / Banca: Ana Helena Januário / Resumo: Fungos endofíticos são microrganismos que colonizam assintomaticamente o interior de plantas, sendo encontrados em órgãos vegetais como as folhas, caule, frutos, sementes e raízes, podendo habitar a planta por toda vida, e são transmitidos, em alguns casos, para futuras gerações através da semente do hospedeiro. Estes exibem interações ecológicas especificas em seu habitat que tem sido pouco exploradas como estratégia para a descoberta de novos produtos naturais bioativos. Entre as varias modificações de meios de cultivo para estimular rotas biossintéticas silenciosas e aumentar a produção metabólica, a técnica OSMAC (One Strain Many Compounds) foi empregada neste trabalho. Colletotrichum gloeosporioides isolado de Eugenia jambolana foi cultivado em dois meios de cultivo sólidos (arroz e milho) e cinco líquidos (Czapek, Malte, Nutrient, PDB e YM), na presença e ausência de rede de polietileno como suporte sólido, objetivando avaliar a variação na produção de metabólitos secundários. Com a variação dos meios de cultivo, foi possível observar grande variação metabólica em todos os meios, o que foi constatado pelas analises por RMN de 1H e CLAE/DAD. Para o cultivo em extrato de malte na presença do suporte sólido (rede de polietileno) foi observado um aumento de massa de aproximadamente 275% no cultivo. Os extratos EjC(05)Arroz, EjC(05)YmSR, EjC(05)MaltSR e EjC(05)MaltCR, mostraram potencial antitumoral contra as linhagens OVCAR (carcinoma de ovário), HCT-116 (cólon humano) e SF-295 (glioblastoma humano). Avaliação de todos os extratos brutos permitiu selecionar o extrato EjC(05)MaltCR para a desreplicação das substâncias produzida, sendo possível identificar as dicetopiperazinas Ciclo Prolina-Valina e Ciclo Prolina-Leucina/Isoleucina. / Abstract: Endophytic fungi are microorganisms that asymptomatically colonize the interior of plants, being found in plant organs such as leaves, stems, fruits, seeds and roots, the plant may dwell for a lifetime, and are transmitted in some cases, for future generations through seed host. These exhibit specific ecological interactions in its habitat that has been little explored as a strategy for the discovery of new bioactive natural products. Among the various modifications of culture media to stimulate and increase silent biosynthetic pathways and metabolic production, OSMAC (One Strain Many Compounds) technique was used in this work. Colletotrichum gloeosporioides isolated from Eugenia jambolana was grown in two different kind of media: two nutrient solids (rice and maize) and five nutrient liquids (Czapek, Malte, Nutrient, PDB and YM) in the presence and absence of polyethylene as a solid support network, to evaluate the variation in the production of secondery metabolites. With the change of the culture media, we observed high metabolic variation in all media, which was corroborated by analysis by 1H NMR and HPLC-DAD. For cultivation in malt extract in the presence of the solid support network (polyethylene) was observed a mass increase of approximately 275% in cultivation. The extracts EjC(05)Arroz, EjC(05)YmSR, EjC(05)MaltSR and EjC(05)MaltCR showed antitumor potential against OVCAR (ovarian carcinoma), HCT -116 (human colon) strains and SF- 295 (human glioblastoma). Evaluation of all crude extracts allowed select the EjC(05)MaltCR for dereplication of substances produced, making it possible to identify the diketopiperazines Cycle Proline-Valine and Cycle Proline-Leucine/Isoleucine. / Mestre

Bacterial type I modular polyketide synthases (PKS) are large multifunctional enzyme systems responsible for the biosynthesis of complex polyketide natural products such as erythromycin, pikromycin, and borrelidin. Type I systems are comprised of a loading module which generally selects an appropriate acyl group starter unit, and multiple discrete extension modules, responsible for each single round of acyl group incorporation into the final polyketide core structure. These modules can exist naturally as either single discrete polypeptides, such as modules 5 and 6 from the pikromycin PKS (PikA3 and PikA4 respectively), or as multimodular polypeptides fused together by short intrapolypeptide linkers such as the loading module and the first and second extension modules of the erythromycin and pikromycin PKSs (DEBS1 and PikAI respectively). While short peptide linkers between modules on the same polypeptide facilitate the transfer of polyketide intermediates from one module to the next via their close proximity to one another, docking domains found at the C-terminus of one module and the N-terminus of the next subsequent module facilitate the needed protein-protein interactions for the passage of biosynthetic intermediates between modules on separate polypeptides. The ability to utilize docking domains in place of intrapolypeptide linkers was explored in the pikromycin and erythromycin PKSs by dissecting the tri-modular PikAI and DEBS1 polypeptides with matched docking domains. It has been shown that PikAI can be separated into two proteins at either of these linkers, only when matched pairs of docking domains from a heterologous modular phoslactomycin PKS are used in place of the intrapolypeptide linker. In both cases the yields of pikromycin produced by the S. venezuelae host mutant, which is a PikAI deletion strain were 50% of that of an S. venezuelae strain expressing the native trimodular PikAI. Additionally, expression of module 2 as a monomodular protein fused to a heterologous N-terminal docking domain was also observed to give almost a 10-fold improvement in the in vivo generation of pikromycin from a synthetic diketide intermediate. The utilization of docking domains to separate linked modules was also demonstrated in the erythromycin PKS. Expression of the first protein involved in erythromycin biosynthesis (DEBS1) with the DEBS thioesterase fused to the C-terminal (DEBS1-TE) in S. venezuelae results in the production of triketide lactone products. Separation of DEBS1-TE resulted in 50% triketide lactone production, consistent with the observations in the pikromycin system. Published work has shown that the DEBS loading module has relaxed substrate specificity, and is capable of incorporating acetate, butyrate and isobutyrate in addition to the normally observed propionate starter unit, which typically predominates. However, in the current study when the DEBS loading module is separated from module 1 with matched docking domains, a dramatic shift in the starter unit, favoring the isobutyrate derived tri-ketide lactone is observed. This apparent shift in starter unit preference for a dissected PKS system has resulted in insights into the kinetics of acyl group loading, off loading, as well as the hydrolysis and transfer from the AT to ACP domains. In addition to the separation of multimodular PKS polypeptides with docking domains, it has also been shown that the individual catalytic domains of single discrete module, BorA5 from the borrelidin PKS can be expressed as stand alone proteins while retaining catalytic functionality in vitro. This work has provided a basis for future studies of this module, which has been proposed to function iteratively, catalyzing three rounds of chain elongation.

A Masters dissertation submitted to the Faculty of Science, University of the Witwatersrand in fulfillment of the requirements of the degree of Master of Science, January 2018 / Modern developments on nanoparticles (NPs) has led to new innovation in nanoparticles that can be used for the treatment of polluted water. Magnetic NPs are of great interest because of their unique properties and promising applications. Their stability is essential to prevent them from agglomeration, hence, modification with a specific coating layer can assist in the selectivity function and stability of the magnetic NPs. In this work, a magnetic organic nano-adsorbent was synthesized and investigated for the application in the extraction of nitroaromatic explosive compounds from aqueous solutions. The approach was to find a possible synergy between the adsorptive properties of Moringa oleifera and the high surface area of the NPs. The magnetic NPs were utilized for their ferromagnetic properties which assist in the extraction procedure. M. oleifera was used as a natural coating agent to functionalize the magnetic NPs and also to provide stability. There are numerous chemical procedures to synthesize magnetite and one of the simplest and convenient procedures, co-precipitation, was used in this study. Magnetite can be easily oxidized under ambient conditions, hence, in order to prevent oxidation, M. oleifera extracts were used as a coating agent. The synthesized uncoated magnetite NPs and M. oleifera coated magnetite NPs were characterized by powder X-ray diffraction (PXRD), Fourier transform infrared (FTIR), Brunauer, Emmett and Teller (BET) and thermogravimetric analysis (TGA). The M. oleifera leaf extract was obtained using pressurized hot water extraction (PHWE) at 80°C and the seed extract was purchased as a pure oil. Both the M. oleifera leaf and seed extracts were characterized by FTIR and gas chromatography–mass spectrometry (GC-MS) for possible organic compounds assisting in the stability of the magnetite. From the BET results of the coated magnetic NPs at different times, it was observed that with increasing coating time, the surface area decreased while the pore size increased. To optimize the extraction of nitroaromatic explosive compounds (NAECs), the parameters that were investigated were sample pH, contact time, mass of adsorbent and initial concentration. The optimum value for pH of the sample was found at pH8 and for the contact time an optimum of 120 min was found. The mass of M. oleifera coated magnetic NPs for the maximum removal of explosives were found to be 100 mg. The adsorption capacity of the NAECs was obtained in the range of 0.45 and 0.76 mg g-1 at optimum conditions. During kinetic studies it was observed that the pseudo second order model explained the extent of the adsorption mechanism. It was observed that the Langmuir model was favourable as compared to the Freundlich model. The order of selectivity for the NAECs studied was observed as follows: 2-NT ≈ 3-NT > 4NT > NB > 2,6-DNT > 1,3-DNB. The limit of detection (LOD) found was 0.37 – 4.47 and 0.45 – 5.66 ng.mL-1 for extraction using magnetic NPs coated with M. oleifera leaf and seed extract, respectively. The percentage recovery for the extraction of NAECs at optimum conditions was obtained in the range 14 – 46%. / XL2018

Although environmental monitoring of polycyclic aromatic hydrocarbons (PAH) is an essential step to prevent human exposure to contaminated sites, it provides little information on the actual human uptake and subsequent risks. To this end, urine analysis of short-term biomarkers such as PAH metabolites fill an important niche. The general approach follows the sequence of urine hydrolysis, sample clean-up and pre-concentration, chromatographic separation and determination. Whereas chromatographic methods are based on well established laboratory techniques, the development of easy-to-use, cost-effective and large sample throughput techniques is becoming increasingly relevant to investigate adverse PAH effects on large human populations. This thesis compares the room-temperature, 77K and 4.2K fluorescence properties of 1-naphthol, 2-naphthol, 1-hydroxypyrene, 2-hydroxyfluorene, 3-hydroxybenzopyrene and 9-hydroxyphenanthrene. These metabolites are used as model biomarkers to investigate the analytical potential of a simple method of analysis based on Solid-Phase Extraction and Room-Temperature Fluorimetry. Metabolites are directly determined in the eluting solvent (methanol) without the need of previous separation via multidimensional formats. Metabolite recoveries varied between 87 ± 1.51% (9-hydroxyphenanthrene) and 99 ± 1.05% (3-hydroxybenzopyrene). For 10mL of urine samples, limits of detection varied between 0.01ng.mL-1 (3-hydroxybenzopyrene) and 0.6ng.mL-1 (2-hydroxynaphthalene). These figures of merit demonstrate the potential of this approach for screening purposes

No / Grammicin 1 from Xylaria grammica is identified as 4-hydroxy-4H-furo[2,3-b]pyran-2(7aH)-one by chemical and physical methods. 4-Oxo-4H-pyran-3-acetic acid (¿-pyrone-3-acetic acid) 2 is a co-metabolite and the conversion of 1 into 2 is discussed.

Thesis (Ph.D.)--Victoria University of Wellington, 2008. / Includes bibliographical references.