Local DNA structures are alternative DNA conformations which can be formed aside from typical B-DNA conformation. These structures often play pivotal roles in regulation of basic biological processes, such as DNA replication, transcription or binding of specific ligands. This biological significance makes alternative DNA secondary structures a potential drug target. In this diploma thesis, local structures in genomes of viruses from Flaviviridae and Retroviridae families are analysed using bioinformatics tools. Furthermore, these structures are visualised using atomic force microscopy.

This master's thesis focuses on search for sequences potentially forming quadruplexes in DNA sequences, their visualization and filtration. For this purpose a web application was created in cooperation with the Institute of biophysics of Academy of science of Czech republic. This application uses a newly created algorithm able to find all possible formations of quadruplex within given input sequence. Design and implementation of this algorithm are also part of this thesis.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18101号 / 理博第3979号 / 新制||理||1574(附属図書館) / 30959 / 京都大学大学院理学研究科化学専攻 / (主査)教授 杉山 弘, 教授 三木 邦夫, 教授 藤井 紀子 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

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Molecular recognition, particularly as it applies to strong binding interactions between complementary ligand/receptor molecules in solution, is important in such varied areas as molecular biology, pharmacology, synthetic chemistry, and chemical detection. Strong binding is the additive result of a number of specific, weak, non-covalent interactions occurring between complementary molecules. This dissertation reports on the energetics of forming complexes between small molecules and model DNA constructs. Ligands included cationic and metallated cationic porphyrins and polyheterocyclic ruthenium compounds. DNA receptors included double stranded B-DNAs (hairpin and short linear sequences) as well G-quadruplex DNAs. Thermodynamic data were collected using isothermal titration calorimetry, circular dichroism spectropolarimetry, ultraviolet-visible spectroscopy, and mass spectrometry. The measured thermodynamic parameters included the changes in free energy, enthalpy and entropy for ligand/receptor complex formation as well as the stoichiometry of the stable complexes. The first section of this dissertation reports that the binding of cationic porphyrins to model G-quadruplex DNA may proceed through two pathways, end stacking and intercalation. Modulating the number of pyridinium groups on a pyridinium substituted porphyrin yielded differing binding thermodynamics leading to the understanding that a balance of surface area, charge, and geometry affect the ability of a porphyrin to bind to G-quadruplex DNA. Further investigations into the binding of metallated porphyrins developed the understanding that the geometry of the central metal ion affected not only the thermodynamics but could also inhibit the intercalative mode. It was previously shown that the high affinity binding for binuclear polyheterocyclic ruthenium compounds proceeds through an intercalative mode. To further understand the binding process and the structureunction relationship of the ligand components, the binding of smaller mononuclear complexes that were representative of portions of the binuclear complex was examined in this dissertation. While limiting the intercalative ability lowered the binding affinity, the mononuclear complex with the full intercalating bridge was able bind to DNA with a higher affinity than the binuclear complex. These studies have been successful in part in determining the contributions of numerous weak interactions including: charge (Coulombic interactions), H-bonding, hydrophobic interactions, and solvent structure (solvation changes), to the overall energetics of this molecular recognition process. The first section of this dissertation reports that the binding of cationic porphyrins to model G-quadruplex DNA may proceed through two pathways, end stacking and intercalation. Modulating the number of pyridinium groups on a pyridinium substituted porphyrin yielded differing binding thermodynamics leading to the understanding that a balance of surface area, charge, and geometry affect the ability of a porphyrin to bind to G-quadruplex DNA. Further investigations into the binding of metallated porphyrins developed the understanding that the geometry of the central metal ion affected not only the thermodynamics but could also inhibit the intercalative mode. It was previously shown that the high affinity binding for binuclear polyheterocyclic ruthenium compounds proceeds through intercalation. To further understand the binding process and the structureunction relationship of the ligand components, the binding of smaller mononuclear complexes that were representative of portions of the binuclear complex was examined in this dissertation. While limiting the intercalative ability lowered the binding affinity, the mononuclear complex with the full intercalating bridge was able bind to DNA with a higher affinity than the binuclear complex. These studies have been successful in part in determining the contributions of numerous weak interactions including: charge (Coulombic interactions), H-bonding, hydrophobic interactions, and solvent structure (solvation changes), to the overall energetics of this molecular recognition process.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第24125号 / 理博第4853号 / 新制||理||1694(附属図書館) / 京都大学大学院理学研究科化学専攻 / (主査)准教授 板東 俊和, 教授 深井 周也, 教授 秋山 芳展 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

京都大学 / 新制・課程博士 / 博士(エネルギー科学) / 甲第24326号 / エネ博第454号 / 新制||エネ||85(附属図書館) / 京都大学大学院エネルギー科学研究科エネルギー基礎科学専攻 / (主査)教授 片平 正人, 教授 森井 孝, 教授 杤尾 豪人 / 学位規則第4条第1項該当 / Doctor of Energy Science / Kyoto University / DGAM

Peptide hormones are important biomolecules that transduce downstream effects such as cell proliferation, regulation, and gene expression. Their levels have been upregulated in various disorders such as cancer, yet detection methods are lacking. We designed two split aptamer-based assays for the detection of a peptide hormone – Somatostatin (SST) – with different signal readouts: fluorescent readout based on light-up aptamers and the colorimetric readout of ABTS peroxidation from a G-quadruplex. We used an already selected split-aptamer –SSTA5–for SST for our designs and we had expected the developed detection systems to exhibit detection and quantification capabilities that would hopefully allow their use for SST monitoring in clinical samples. However, our experiments did not support the hypothesis of this project and SST was not able to be detected using either of our fluorescent or colorimetric methods. To determine if the SSTA5 aptamer could bind SST appropriately, Förster resonance energy transfer (FRET) was used. We verified that there was no energy transfer between two covalently-attached light-sensitive molecules (one attached to each part of the split SSTA5 aptamer); thus, we theorize that the aptamer does not hybridize in the presence of the tetra decapeptide SST. Therefore selection of another, more appropriate, aptamer for SST will be needed for further aptameric-based detection methods. Once this is accomplished, our methodologies could be re-applied for detection of SST which could lead to real-time detection of essential hormonal levels in patients.

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