Inspirados em reações catalisadas por enzimas a partir de micro-organismos encontrados em ambientes marinhos severos (psicrofílicos), em que a quantidade de oxigênio é restrita, observou-se que a Arthrobacter sp. CCT 7749 realizou diferentes transformações químicas mudando de condições reacionais anaeróbias para aeróbias. Dependendo da presença ou ausência de oxigênio, ambas desracemização de alcoóis ou redução de cetonas com seletividades enantiocomplementares foram realizadas pelo mesmo microorganismo. Estes conceitos foram aplicados tanto para desracemização quanto para redução enantiosseletiva de compostos contendo heteroátomos (silício, fósforo, estanho e boro). Visando a identificação molecular das enzimas responsáveis pelas reações de oxido-redução, buscou-se desenvolver uma metodologia de purificação enzimática usando diferentes técnicas. Inicialmente a lise celular da Arthrobacter sp. CCT 7749 empregando a liticase na presença de β-mercaptoetanol e usando ondas ultrassônicas produziu 28 mg/mL de proteínas. A purificação da oxidorredutase ocorreu através de colunas cromatográficas de troca iônica DEAE FF, seguida por ANX FF. O extrato protéico contendo a enzima parcialmente pura apresentou atividade específica de 4,23 U/mg na oxidação do (R,S)-1-(4-metilfenil)etanol à cetona correspondente. Através do uso das técnicas native-PAGE e zimografia detectou-se uma massa molecular da enzima de ≈240 kDa e que provavelmente se encontrava na forma hetero-hexamérica apresentando três subunidades em ~35 kDa e três em ~45 kDa. Observou-se que, surpreendentemente, a fração protéica parcialmente pura também foi capaz de reduzir a 4-metilacetofenona obtendo-se 17% do (S)-1-(4-metilfenil)etanol com excelente excesso enantiomérico >99%. / Inspired by enzyme-catalyzed reactions with microorganisms found in harsh marine environments (psychrophilic), in which the amount of oxygen is restrict, we have shown that Arthrobacter sp. CCT 7749 can perform different chemical transformations by switching from anaerobic to aerobic reaction conditions. Depending on the presence or absence of oxygen, either alcohol deracemization or ketone reduction with enantiocomplementary selectivities can be performed by the same microorganism. These concepts were applied for both deracemization and enantioselective reduction of heteroatom-containing molecules (silicon, phosphorus, tin and boron). Aiming Enzyme purification, different techniques were employed. Cell lysate of Arthrobacter sp. CCT 7749. Was prepared using lyticase and β-mercaptoethanol bu ultrasonication. Purification of this enzyme occurred through chromatographic columns of DEAE FF ion exchange, followed by ANX FF. The partially pure oxidoreductase presented specific activity of 4.23/mg in the oxidation (RS)-1-(4- methylphenyl)ethanol to the corresponding ketone. Native-PAGE and zymography have shown that the enzyme had ≈240 kDa molecular mass, probably in the form hetero-hexameric with 3 subunits ~35 kDa and three ~45 kDa. Surprisingly, the partially pure protein fraction was able to reduce the 4- methylacetophenone giving 17% of (S)-1-(4-methylphenyl)ethanol with excellent enantiomeric excess >99%.

This thesis describes the efforts towards the synthesis of the guaiane-6,12-olide skeleton, which characterises the guaianolide family of bioactive natural compounds. Two approaches have been investigated: the intramolecular hetero Diels Alder (IMHDA) reaction and the intramolecular carbonyl ene reaction. This thesis has been divided in three sections: the first part gives a general background about the guaianolides, the second section describes the synthetic approaches we investigated and, finally, the third section reports the experimental details. The first section gives a brief overview about the biosynthesis, the biological activities of the guaianolides, and the most interesting synthetic approaches to obtain them. The second section describes the two different approaches we investigated and gives a theoretical background about the main chemical transformations used. At first, the IMHDA reaction approach is described: a brief overview of palladium catalysis and Diels Alder reaction is given, and it is followed by the results and discussion of our study. Similarly, a theoretical background of the Alder ene reaction is given, before the results and discussion of the intramolecular carbonyl ene reaction approach are described: particular importance is given to the reasoning that led to the assignment of the relative configuration of the cycloadducts obtained, and to the rationalisation of this stereochemical outcome. Finally, the third section gives a complete description of the experimental procedures followed, and of the experimental data for the synthetic studies performed in the previous chapter.

No description available.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19725号 / 工博第4180号 / 新制||工||1645(附属図書館) / 32761 / 京都大学大学院工学研究科材料化学専攻 / (主査)教授 松原 誠二郎, 教授 中尾 佳亮, 教授 杉野目 道紀 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

The accumulation of microplastics (MPs) are a growing concern for the environment, the maximum contributor to the MP pollution is tyre wear particles or TWPs. TWPs can accumulate in the environment and remain there for long periods of time and hence have the ability to disrupt ecosystems. With nearly 6,000,000 tons of TWPs being emitted each year globally there is a need to study theiroccurrence and fate in terms of why and how these particles get created and where they end up in the environment. The occurrence and fate of tyre wear particles (TWPs) were investigated, and a model was created in Python to simulate the flow of TWPs in a stormwater system at a test site on Highway E18 in Sweden. In the literature review it was found that the generation of TWPs is highly dependent on annual average daily traffic and the type of the road; it is also dependent on the driving behaviour such as acceleration, making unnecessary turns and the use of studded tyres in the winter. The TWPs are generally transported via stormwater but wind also plays a crucial role in transporting TWPs which are of a smaller size than 10 µm. Although the common notion is that the TWPs get washed into rivers,the literature review also suggests that most TWPs get trapped in soil that is covered with vegetation. Three processes were simulated in the developed model, namely transport, hetero-aggregation and settling. The results clearly show that a rainfall with an intensity of 40 mm during 15 min providesminimum settling in the stormwater system, and a 10 mm rainfall with a duration of more than 30 hasmaximum settling. Hetero-aggregation and settling is directly dependent on particle size and hence larger particle sizes have a higher probability of attaching to another particle or to settle in the pipes or wells of the stormwater system. It was also observed that the flow patterns such as depth, discharge and velocity of flow largely affect the settling and hetero-aggregation in the stormwater system. Most particles remain unaffected in short duration and high intensity rainfalls; the opposite is true for the longer duration and lower intensity rainfalls. Using the model, a stormwater system can be designed to trap or to flush out TWPs from the system. Also, the concentration of TWPs in the sinks can be known using the model that is created in this study

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Motivation: Understanding how nucleic acids interact is essential for understanding their function. Controlling these interactions, for example, can allow us to detect diseases and create new therapeutics. During quantitative reverse-transcription polymerase chain reaction (qRT-PCR) testing, having nucleic acids interact as designed is essential for ensuring accurate test results. Accurate testing is an important consideration during the detection of COVID-19, the disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Results: I introduced the program DinoKnot (Duplex Interaction of Nucleic acids with pseudoKnots) that follows the hierarchical folding hypothesis to predict the secondary structure of two interacting nucleic acid strands (DNA/RNA) of similar or different type. DinoKnot is the first program that utilizes stable stems in both strands as a guide to find the structure of their interaction. Using DinoKnot, I predicted the interaction structure between the SARS-CoV-2 genome and nine reverse primers from qRT-PCR primer-probe sets. I compared these results to an existing tool RNAcofold and highlighted an example to showcase DinoKnot’s ability to predict pseudoknotted structures. I investigated how mutations to the SARS-CoV-2 genome may affect the primer interaction and predicted three mutations that may prevent primer binding, reducing the ability for SARS-CoV-2 detection. Interaction structure results pre- dicted by DinoKnot that showed disruption of primer binding were consistent with a clinical example showing detection issues due to mutations. DinoKnot has the potential to screen new SARS-CoV-2 variants for possible detection issues and support existing applications involving DNA/RNA interactions, such as microRNA (miRNA) target site prediction, by adding structural considerations to the interaction to elicit functional information. / Graduate

Yes / Metal nanocrystals offer new concepts for the design of nanodevices with a range of potential applications. Currently the formation of metal nanocrystals cannot be controlled at the level of individual atoms. Here we describe a new general method for the fabrication of multi-heteroatom-doped graphitic matrices decorated with very small, ångström-sized, three-dimensional (3D)-metal crystals of defined size. We irradiate boron-rich precious-metal-encapsulated self-spreading polymer micelles with electrons and produce, in real time, a doped graphitic support on which individual osmium atoms hop and migrate to form 3D-nanocrystals, as small as 15 Å in diameter, within 1 h. Crystal growth can be observed, quantified and controlled in real time. We also synthesize the first examples of mixed ruthenium–osmium 3D-nanocrystals. This technology not only allows the production of ångström-sized homo- and hetero-crystals, but also provides new experimental insight into the dynamics of nanocrystals and pathways for their assembly from single atoms. / We thank the Leverhulme Trust (Early Career Fellowship No. ECF-2013-414 to NPEB), the University of Warwick (Grant No. RDF 2013-14 to NPEB), the Swiss National Science Foundation (Grant No. PA00P2_145308 to NPEB and PBNEP2_142949 to APB), the ERC (Grant No. 247450 to PJS), EPSRC (EP/G004897/1 to RKOR, and EP/F034210/1 to PJS) and Science City (AWM/ERDF) for support. We thank the Wellcome Trust (Grant No. 055663/Z/98/Z) for funding the Electron Microscopy Facility, School of Life Sciences, University of Warwick. We also thank COST Action CM1105 for stimulating discussions, Thomas Wilks for supplying the micelle image for Figure 1, and the Australian Synchrotron and the University of Monash for allocation of time on the SAXS/ WAXS beamline and funding. The 2000FX Gatan Orius digital TEM camera used in this research was funded by Science City: Creating and Characterizing Next Generation Advanced Materials, with support from Advantage West Midlands and part funded by the European Regional Development Fund.

The tree and shrub species belonging to the Myrtaceae family are rich in structurally diverse meroterpenoids which possess anti-cancer, anti-malarial, anti-bacterial, anti-viral, and anti-inflammatory biological activities. Many of the natural products belonging to this family are derived from two common precursors: syncarpic acid and formyl phloroglucinol. The dissertation research described herein is focused on the total synthesis of two subclasses of natural products: syncarpic acid-derived meroterpenoids and formyl phloroglucinol meroterpenoids. The synthetic methodologies disclosed were developed to enrich the chemodiversity of these novel meroterpenoids by providing efficient access to such scaffolds and derivatives. Rhodomyrtusials A–C, the first examples of syncarpic acid-derived sesquiterpene meroterpenoids featuring a unique 6/5/5/9/4 fused pentacyclic ring system, were isolated from Rhodomyrtus tomentosa along with several biogenetically-related dihydropyran isomers. Two bis-furans and one dihydropyran isomer showed acetylcholinesterase (AChE) inhibitory activity. Herein, the bioinspired total syntheses of six isolates were achieved in six steps utilizing a reactive enetrione intermediate generated in situ from a readily available hydroxy-endoperoxide precursor are reported. Further evaluation of alkene reaction partners identified additional modes of reactivity for the enetrione, leading to the production of novel small molecule scaffolds. Furthermore, computational studies have identified a valid asynchronous, concerted pathway leading to the formation of the bis-furan containing natural products. Eucalyptusdimers A−C, three dimeric phellandrene-derived formyl phloroglucinol meroterpenoids featuring an unprecedented, fused skeleton between two phellandrene and two acylphloroglucinol subunits, along with one biogenetically related intermediate eucalyprobusone A, were isolated from the fruits of Eucalyptus robusta. These isolates also showed AChE inhibitory activity. A one-pot, three-component reaction was identified to achieve the synthesis of eucalyprobusone A and subsequent synthetic efforts towards eucalyptusdimers A and B via hetero-Diels Alder (HDA) [4+2] cycloaddition with known terpene, alpha-phellandrene are outlined. Initial efforts failed to promote the desired HDA cycloaddition, which led to alternate exploration of oxidative [4+2] cycloaddition chemistry. Using this revised strategy, the synthesis of several Eucalyptus metabolites including grandinol, euglobal IIc, and euglobal T1 was achieved. Future efforts and synthetic strategies to afford the eucalyptusdimers from these precursors are provided. / 2025-09-20T00:00:00Z

No description available.