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Coming dissertations at Uppsala university

  • Computational Ecotoxicology Author: Sergio Manzetti Link: Publication date: 2022-05-18 16:06

    Human society has progressed by polluting ecosystems since at least the early industrialrevolution. Large amounts of harmful chemical compounds have been dispersed in soils, seas,ground waters and wildlife habitats by industrial and anthropomorphic activities over the lasttwo centuries, leading to a persistent toxicological load on the environment. Pollution is athreat to biodiversity, to the health of ecosystems, and to all living organisms. Advancesin environmental sciences are needed so that pollutants can be distinguished from harmlesscompounds. New methods could ease the enormous task of sorting out hazardous chemicals,and also facilitate the study of existing problems in ecotoxicology, which are often hampered byinsufficient data. In our research, we apply the methods of computational chemistry to predictthe interactions of various toxins, carcinogens, nanoparticles and xenobiotics with proteins,DNA, and cell membranes. Methods such as molecular dynamics simulations, docking, andquantum chemistry are at the core of these studies, each having its role in facilitating theenormous task of transforming in vitro ecotoxicology to in silico ecotoxicology. We performdetailed studies of a few compounds and receptors, as well as larger, more comprehensive groupsof compounds. We also outline approaches for drawing computational conclusions about themolecular behaviour of various potential environmental toxins by modelling their interactionswith DNA and proteins, and we use partition coefficients to describe their ability to permeate thecell membrane. Methods for studying the purification of pollutants from essential sources, suchas water, are proposed. We also investigate the emerging problem of nanoparticle pollution andpropose computational approaches to model the formation of nanoparticles from combustionemissions and the interactions of such particles with atmospheric components.

  • An exploration of freshwater microbial ecology : from streamlined genera to global networks Author: Rhiannon Mondav Link: Publication date: 2022-05-18 14:25

    Microbes are the main drivers of biogeochemical cycles on Earth and even though freshwaters cover only a small area of terrestrial surfaces their contribution to global cycles is important. Global cycles are measured by exchanges between systems e.g. water to atmosphere or lithosphere and are mediated by microbial communities. Cyanobacteria and other photosynthetic microbes can be highly abundant going through cyclic blooms. These blooms are attributed to their ability to harness sunlight and CO2 to outgrow competitors by using their complex and expensive to produce photosystems. In contrast there are microbial lineages termed ‘streamlined’, that are just as abundant as cyanobacteria at times, but who have much smaller cells, small genomes, and grow and replicate slowly. It is not immediately apparent how microbes with such different lifestyles can have similar ‘success’. By investigating individual streamlined lineages and their interactions we see that they appear to have co-evolved dependencies with each other and are highly successful as consortia. By comparing consortia from different lakes we see that streamlined microbes can sit either adjacent or in the middle of carbon cycling end-points and may be more directly involved than thought in mediating methane and CO2 ratios. An analysis of global inland water microbiomes finds that around one third of the core microbial lineages in inland waters are streamlined.

  • Discovery of Secondary Metabolites from Rwandese Medicinal Plants : Isolation, Characterization and Biological Activity Author: Daniel Umereweneza Link: Publication date: 2022-05-18 14:01

    Plants have served as the principal source of medicines in different parts of the world through the ages. Herb-derived medicines have been used as decoctions, infusions, tinctures or single substance drugs. Due to their impressive possibility of diversification, plants have also provided an immense universe of creativity for synthetic chemists, who constantly make useful new molecules inspired by the natural molecular architecture.

    The goal of this thesis work was to investigate secondary metabolites isolated from selected Rwandese medicinal plants. It focused specifically on the isolation, the characterization and the determination of the biological activity of natural products. The investigated plants belong to the families of Myrtaceae (Eucalyptus melliodora and Eucalyptus anceps), Fabaceae (Eriosema montanum), Lamiaceae (Clerodendrum myricoides) and Asteraceae (Senecio mannii). These were selected from the Rwandese flora based on information collected from traditional healers, and from the literature. The study made use of chromatographic, spectroscopic and spectrometric methods for separation, purification and structure elucidation of the plant constituents.

    In paper I, the chemical composition and antifungal activity of essential oils of E. melliodora and E. anceps were discussed. The essential oils were composed of mono- and diterpenes, and their alcohol derivatives. The essential oil mixtures exhibited antifungal activity against food spoilage fungi.

    In paper II, E. montanum was investigated and a total of 20 compounds were isolated including two new prenylated dihydrochalcones and eighteen known secondary metabolites. Their antibacterial activities and cytotoxicity were determined. 

    In paper III, the isolation of three new and two known iridoid glycosides from C. myricoides was reported along with the antiviral activities of the crude extract and of the isolates. 

    In paper IV, the phytochemical investigation of S. mannii was reported. It afforded one new silphiperfolanol angelate ester, two new macrocyclic pyrrolizidine alkaloids, and five known secondary metabolites. Two new synthetic derivatives were obtained by structural modification of 2-angeloyloxy-5,8-dihydroxypresilphiperfolane. The relative stereochemistry of senaetnine was investigated by NAMFIS and confirmed to be 7R, 12R, and 13R.

    The new compounds isolated in this study have shown biological activities, and may provide lead compounds for drug discovery and technological applications.