Master Degree / Yüksek Lisans Tezleri

Permanent URI for this collectionhttps://hdl.handle.net/11147/3008

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Department: search.filters.department.Thesis (Master)--İzmir Institute of Technology, Molecular Biology and GeneticsSubject: search.filters.subject.Oxidation

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  • Master Thesis
    The Rational Design of a Novel Biocatalyst Using the Heme-Nitric Oxide/Oxygen Binding Protein
    (Izmir Institute of Technology, 2017) Meşe Özçivici, Gülistan; Meşe Özçivici, Gülistan; 04.03. Department of Molecular Biology and Genetics; 04. Faculty of Science; 01. Izmir Institute of Technology
    Recent advances in recombinant DNA technology and protein design have led to the application of biocatalysis as an alternative to chemical catalysis in the synthesis of enantiopure products due to high regio- and enantioselectivity. Hemeproteins are proteins with a heme prosthetic group that play diverse roles in biological systems, making them good candidates for biocatalysis. The Heme-nitric oxide/oxygen binding (H-NOX) protein was identified by homology to the soluble guanylate cyclases. Here, the H-NOX domain from the methyl-accepting chemotaxis protein, Thermoanaerobacter tencogenesis (TtH-NOX), was tuned into a biocatalyst using rational design. Four variants of TtH-NOX were cloned, purified and characterized. Each variant was then tested for their catalase and peroxidase activities. The wild type TtH-NOX inefficiently catalyzed the hydrogen peroxide decomposition (catalase activity) and 2,2’-azino-bis(3- ethylbenzthiazoline-6-sulfonic acid (ABTS) oxidation (peroxidase activity). However, the Y140H mutant exhibited an efficient five-fold increase in catalase and peroxidase activities as compared to the wild type. The other mutants, H102Y, H102C and Y140A TtH-NOX, were not good catalysts for both reactions. Therefore, the mutations resulted in changes in reaction rates and electronic properties of the heme group. The mutations affected the molecular mechanism of the hemeprotein, showing that both the proximal and distal pocket residues are vital for catalysis. However, the mutation of the distal tyrosine to histidine of TtH-NOX has significantly improved its catalytic activities. These observations contribute to the understanding of the physiological roles of hemeproteins. This project could also lead to discovery of novel biocatalysts and aid in the design of future biocatalysts.
  • Master Thesis
    Physiological and Biochemical Characterization of Drought Tolerance in Chickpea
    (Izmir Institute of Technology, 2012) Keskin, Hilal; Frary, Anne; Frary, Anne; 04.03. Department of Molecular Biology and Genetics; 04. Faculty of Science; 01. Izmir Institute of Technology
    Chickpea (Cicer arietinum cv. Gokce.) is an agronomically and economically significant plant for Turkey. It is successfully grown under severe drought conditions which limit the growth of other plants. It is generally affected by terminal drought which causes retardation of flowering and decreases yield in Mediterranean and subtropical climates. The aim of this study was to determine significant factors which can be used to identify chickpea plant tolerance to drought stress. With this objective we assessed physiological (fresh and dry weight, relative and real water content) and biochemical (enzymatic and non-enzymatic antioxidants, malondialdehyde, total protein and phytohormone contents) parameters which were used to measure the impact of drought on chickpea. To determine drought's effects, we collected stressed (drought treated) and control (non drought treated) samples from the chickpea cultivar Gokce. Results showed that both fresh and dry weights of plants increased while real and relative water contents of plants decreased under drought stress. There was an increase in both malondialdehyde (MDA) and total protein contents under drought stress. Furthermore, glutathione reductase (GR) and catalese (CAT) enzyme activity increased in drought treated plants whereas guaiacol peroxidase (POD) and superoxide dismutase (SOD) enzyme activity decreased. Moreover, contents of indole acetic acid (IAA) and abscisic acid (ABA) increased in all tissue parts while contents of salicylic acid (SA), gibberellic acid (GA) and jasmonic acid (JA) increased in specific plant tissue parts during drought treatment. In conclusion it is obvious that all of these characters play essential roles in the drought tolerance of plants.