|
|
Preparation of Ethyl 2-acetoxypropanoate
Kučerová, Eliška ; Pospíšilová, Aneta (referee) ; Figalla, Silvestr (advisor)
The bachelor thesis focuses on the preparation of ethyl 2-acetoxypropanoate as a potential nonpolar biosolvent. Selected preparation should provide the highest yield possible. For this purpose, a theoretical review of possible syntheses was developed, with emphasis on syntheses based on acetylation of ethyl lactate. The experimental part of the work then focuses in more detail on the possibility of isolating ethyl 2-acetoxypropanoate from the reaction mixture. Product isolation was verified by fractional distillation and extraction method. In the isolated product, the basic physical properties were determined and the spectrum measured by Fourier transformation infrared spectroscopy. Furthermore, the hydrolytic stability of ethyl 2-acetoxypropanoate was investigated and a series of calorimetric measurements were performed. From these measurements, the effect of reaction temperature on reaction rate and product conversion and the effect of catalyst presence was assessed.
|
|
|
Vliv chemické modifikace na vybrané vlastnosti dřevěné pružiny
Novák, Filip
This thesis focuses on the influence of chemical modification on a wooden spring.The spring was made of beech wood (Fagus sylvatica, L.). Bending ratio was chosen 1:4 thickness to radius. The effectiveness of the chemical modification with acetic anhydride was measured by weight percentage gain (WPG). Acetylation was made with 18 % WPG (at full acetylation 25 % WPG was observed damage of bent wood mostly by compression stress). Chosen spring properties was evaluated in four moisture states (dry, in condition of 65 %, 85 % and 99 % relative humidity and temperature 20 °C). Influence of acetylation on mechanical properties was proven. In wet condition acetylated samples proved higher shear modulus of elasticity a higher rigidity of spring. In dry condition acetylated samples proved lower shear modulus of elasticity a lower rigidity of spring. Influence of acetylation on dimension stability was proven. Acetylated samples proved reduction of equilibrium moisture content (46-56 %) in comparison to reference samples. Acetylated samples proved swelling reduction in radial direction (41-56 %) and in tengential direction (46-59 %). More regular swelling (ratio of radial and rangential) was observed at acetylated samples. Influence of acetylation on shape stability was proven. Shape stability of acetylated spring was evaluated by change in diameter of spring in different moisture states. Wet conditions caused enlargement of acetylated spring diameter (5-16 %) and of reference spring diameter (10-40 %). Reduction of shape changes was observed (57-75 %).
|
|
|
Stanovení koeficientů tepelné vodivosti modifikovaného dřeva buku
Stárek, Šimon
The bachelor thesis is dedicated to the influence of selected wood modifications on its thermal properties. For the experimental part of the work, European beech wood (Fagus sylvatica L.) was used, which was modified by acetylation (using acetic anhydride) and thermal modification at temperatures of 200 and 220 ˚C. Values of thermal conductivity coefficient, specific heat capacity, and thermal diffusivity were measured using the Thermophysical Tester RTB device. The obtained data were statistically evaluated and compared with available literature. Compared to control samples, a decrease in thermal conductivity of approximately 3 % was observed in samples thermally modified at 200 ˚C. Samples thermally modified at 220 ˚C showed much significant decrease in thermal conductivity, that being over 15 %, due to a more pronounced decrease in the density of the modified wood. Despite the fact that the density of acetylated samples increased, very similar results were achieved. This decrease in thermal conductivity was mainly caused by the different thermal properties of the chemical used for impregnation process. Modified wood with these thermal properties can find applications in the construction industry, where the priority is to achieve the best possible energy efficiency of components made of wood.
|
|
|
Vliv tepelné a chemické modifikace na sorpční, difuzní a hygroexpazní vlastnosti dřeva
Imramovský, Pavel
This thesis dealed with the influence of heat and chemical modification on sorption, diffusion and hygroexpansion properties of wood. To this aim, a thermal modification of European beechwood was carried out at temperatures (180 °C, 200 °C, 220 °C) in the special modified chamber of Katres. Furthermore, chemical modification was required on individual samples using acetic acid anhydride. The individual samples had to be sliced in radial and tangential directions using microtoma. A dynamic vapour sorption (DVS) device was used to determine the sorption and diffuse properties of all these beech slices as well as the reference unmodified sample. In addition, dynamic swelling was determined for all groups studied in radial and tangential directions. In order to determine the rate of swelling, sample sizes were measured using a scaler in specified directions before and after the 24-hour period in the water. The results indicated that both heat- and chemically-treated beechwood scored better against moisture than reference untreated samples. The diffusion coefficient in the radial direction was also higher than in the tangential direction, which corresponds to the professional literature. The results indicate that heat- and chemically-treated beechwood resisted better moisture than the reference untreated samples. Within swelling, direction plays a large role, as measurements in the tangential direction are nearly twice as high as the radial. The possibilities of using modified wood in construction as well as from the perspective of the researched characteristic were considered. The statistics were performed in the ANOVA program.
|
|
|
Differences in histone acetylation in normoxia and hypoxia
Čepek, Pavel ; Poljaková, Jitka (advisor) ; Eckschlager, Tomáš (referee)
Histones and their N and C terminal tails undergo different covalent modifications that regulate gene transcription. Among these histone modifications are methylation, ubiquitinilation, SUMOylation, ADP- ribosylation, phosphorylation, proline izomerization, deimination and acetylation. Histone acetylation is regulated by histonacetyltransferases (HATs) and histondeacetylases (HDACs). The balance between acetylation/deacetylation influences chromatin condensation and thus regulates gene transcription. Acetylation balance is disrupted in many human cancers and this fact can contribute to the development of malignant diseases. Histondeacetylase inhibitors (HDACi) can restore this acetylation imbalance. One of these HDACi is valproic acid (VPA) which has been used in treatment of epilepsy for decades. VPA shows antitumour effect in many studies. Decreased expression of n-myc oncoprotein, inhibition of tumour growth and angiogenesis are one of these anticancer effects observed in neuroblastoma cell lines after treatment with VPA. Despite the fact that exact mechanism of antitumour effect of VPA remains unclear, one of the most important mechanisms is hyperacetylation of histone H3 and H4. It is shown in this work that VPA increases acetylation of histones H3 and H4 in human neuroblastoma cell lines...
|
|
|
Preparation of organocatalysts derived from monosaccharides
Nekvinda, Jan ; Veselý, Jan (advisor) ; Trnka, Tomáš (referee)
This bachelor thesis is focused on the synthesis of organocatalysts derived from monosaccharides, in particular D-glucose and D-glucosamine, with various protecting groups. Synthesis of various thiourea catalysts and the attempt to prepare new squaramide catalysts is described. ABSTRAKT Tato bakalářská práce je zaměřena na syntézu organokatalyzátorů odvozených od monosacharidů, zejména z D-glukózy a D-glukosaminu, s různými chránícími skupinami. Dále je popsána syntéza různých thiomočovinových katalyzátorů a pokus o přípravu katalyzátoru obsahující derivát kyseliny čtvercové.
|
|
|
The role of acetylation in the RNA recognition motif of SRSF5 protein
Icha, Jaroslav ; Staněk, David (advisor) ; Šenigl, Filip (referee)
Acetylation is emerging as an important posttranslational modification, which is found in thousands of proteins in eukaryotes, as well as prokaryotes. Global proteomic studies implicated acetylation in regulation of various processes like metabolism, gene expression, cell cycle or aging to name a few. In this work I set out to investigate the role of acetylation of a splicing regulatory protein SRSF5 by creating mutations in its acetylation site. I tested the hypothesis that acetylation influences SRSF5 interaction with RNA. I expressed acetylation-mimicking (Q) or non-acetylable (R) mutant of SRSF5 in HeLa cells and measured their interaction with RNA by RNA immunoprecipitation or in vitro by fluorescence anisotropy. Both approaches agreed that mutants interact with RNA less than the wild type protein and Q mutant bound RNA weaker than R mutant. I did not detect further difference in localization or dynamics among the proteins in vivo, which suggests that difference caused by weakened interaction of mutants with RNA was outweighed by other factors influencing SRSF5 behaviour, probably protein-protein interactions. I also found out that mutant SRSF5 proteins do not have a dominant effect on splicing of fibronectin alternative EDB exon. The data obtained give an indirect evidence for the hypothesis that...
|
|
|
The relationship between splicing and posttranslational modifications of chromatin in Saccharomyces cerevisiae
Kovaľová, Libuša ; Folk, Petr (advisor) ; Čáp, Michal (referee)
Protein Prp45, the yeast ortholog of the human transcription coregulator SNW1/SKIP, has been previously associated only with the regulation of pre-mRNA splicing. However, our laboratory found that protein Prp45 genetically interacts not only with the proteins involved in pre-mRNA splicing, but also with factors important for transcription elongation and with chromatin modifying enzymes. Our data and the information about the human ortholog SNW1/SKIP suggest that Prp45 could serve as a regulator coupling splicing, transcription and chromatin state in S. cerevisiae. The main aim of this diploma thesis was to find out whether the protein Prp45, which is essential for cotranscriptional assembly of the spliceosome, affects posttranslational modifications of chromatin on transcribed genes. Using chromatin immunoprecipitation, the influence of prp45(1-169) mutation on trimethylation of histone H3 at lysine 4 and acetylation of histone H3 at lysines 9, 14 and 18 on transcriptionally active genes was not confirmed. The other aim was to analyse the behavior of cells synchronized by α-factor by using flow cytometry. According to our results, prp45(1-169) mutation leads to the prolongation of the cell cycle. For the purpose of monitoring the dynamics of nucleosomes in S. cerevisiae strains, the system of...
|
|
|
Virulence of Bordetella pertussis from an Omics Perspective
Novák, Jakub ; Šebo, Peter (advisor) ; Černý, Jan (referee) ; Novák, Petr (referee)
The Gram-negative aerobic coccobacillus Bordetella pertussis is one of the few exclusively human pathogens and the main causative agent of the respiratory infectious disease called pertussis, or whooping cough. Despite global vaccination programs, pertussis remains an important public-health burden and still accounts for over 100,000 infant deaths and over a dozen of millions of whooping cough cases every year. Substantial effort is devoted to studies on the mechanisms of action of virulence factors of B. pertussis, but the biology of interactions of B. pertussis with its human host remains largely underexplored. Evolution, genetics and adaptation of B. pertussis to the complex environment of human nasopharynx and the mechanisms enabling B. pertussis to overcome host innate and adaptive mucosal immune defenses, remain poorly understood. In such situations, unbiased exploratory omics approaches represent valuable tools for uncovering of unknown aspects of host-pathogen interactions and open the path to detailed analysis of virulence-underlying processes by mechanistic studies. In this thesis, I am presenting the results of three omics projects on B. pertussis biology that involved high-throughput proteomics. In the inital phosphoprotemics project, we analyzed the kinase signaling pathways hijacked...
|
|
|
Wood impregnation
Pařil, Petr
Wood impregnation is one of the oldest and the most frequently used techniques to protect the wood. This treatment offers a wide range of protection depending on used impregnants (preservatives). Impregnation can make the wood more resistant to decay, less flammable, more dimensionally stable, harder, stronger, more UV stable resistant and many more. Generally, the aims of this thesis is to give a new and modern approaches to already known technologies. The experimental part have been carried out using laboratory vacuum-pressure impregnation plant and many other devices. Almost all treatments and measurement have been done in laboratories of Research centre in Útěchov. The different wood species e.g. European beech (Fagus sylvatica L.) and hybrid poplar (Populus hybrids) have been studied. The patented solution shows the method of the treatment and colouring of wood containing tannins, characterized by impregnation with a product containing iron oxide nanoparticles, in a concentration of 0.4 g/l to 42 g/l, an average particle size in the range of 1 to 100 nm, and a liquid medium. Impregnation can be performed as pressure impregnation, followed by soaking, or the product can be applied by brushing or spraying. This method is an alternative to wood ammonification. The tests (Paper I) shows following results. Both nanoiron and ammonia treatments tested induced darker colouring of oak wood, more intensive darkening was observed in case of the nano-iron treatment. The native oak showed a steep drop in lightness ca 25-50 hours of exposure followed by gradual re-increase during further exposure to the artificial sunlight. The darker surfaces generated by tannin reacting chemically with iron and ammonia evidently faded in the course of light exposure. In case of chromatic parameters a* and b*, the AT (ammonia treatment) oak more or less copied the colour change progress of native oak. On the contrary, the NIT (nanoiron treatment) wood showed a double increase in both parameters. The colour of NIT wood after light exposure was more or less equivalent to the original colour of the ammonium-treated. Distinct reddening of NIT oak may be caused by oxidation of non-precipitated iron particles. The antifungal effects of copper and silver nanoparticles against two wood-rotting fungi were investigated with following results (Paper II). The highest value of retention was observed for pine sapwood (~ 2 kg/m3) for both nanoparticle solutions. The amount of nanoparticles in the wood did not increase proportionally with an increasing concentration, but only 1.5-2 times increase was reached. An average leaching of 15% to 35% was observed for copper nanoparticles, depending on used wood species and concentration. Significantly lower leaching (max. 15 %) was observed for pine sapwood impregnated by silver nanoparticles with a concentration of 3 g/l. The highest antifungal effect (under 5 % of mass loss) against both tested fungi was found for nano-copper treatment at the concentration of 3 g/l. However, this effect of treatment seems to be almost negligible after the leaching test. Therefore, this study aims to present fundamental material properties of wood treated with copper and silver nanoparticles, and provide groundwork for further research (e.g. fixation of substances in the wood structure, etc.). In this study (Paper III), selected physical and mechanical properties, i.e., density profile, bending strength, hardness and moisture absorption were investigated for Lignamon (i), which was obtained from the Czech industrial production. Selected properties were also investigated using steam-densified beech (ii) and native beech (iii) and compared with each other. Densitometry of Lignamon showed a large variability of the density profile compared to the density profile of only densified beech. It is affected by the degree of densification, temperature and moisture gradients, and their relationship to the glass transition of the wood cell wall. Modulus of elasticity, hardness, moisture exclusion and anti-swelling efficiency of Lignamon are enhanced compared to densified beech. The enhanced dimension stability and lower hygroscopicity of Lignamon are probably caused by heat treatment during the process. Further investigation will be carried out with self-produced Lignamon samples. The paper IV deals with the effect of vacuum-pressure impregnation of poplar wood (Populus alba L.) by aqueous solutions of sucrose and sodium chloride on its physical properties. The most satisfying final properties were achieved in impregnation of sucrose with concentration of 6.25 g/100 ml H2O. The retention was 31 kg/m3 (WPG around 8 %). The values of ASE (anti-swelling efficiency) reached to 36 % and MEE (moisture exclusion efficiency) was reduced by 33 %. In Paper V, MW and conventional acetylation of wood was carried out to determine its efficacy on the material properties. Both MW and conventional heating positively affected the selected material properties. The results showed that no significant differences were found between MW and conventional heating; therefore, MW heating can be used as a valid replacement in the acetylation process. MW power of 2 kW and 0.1 m/min conveyor speed were the optimum conditions for MW acetylation. These process parameters resulted in 39.4 % ASE (T) and 35.2 % ASE (R) for beech and 38.0 % ASE (T) and 16.3 % ASE (R) for poplar samples. This work provides insight into the details of wood acetylation using MW heating. The study (Paper VI) aims to evaluate the antifungal activity of extractive compounds obtained with fexIKA accelerate extraction process. Results showed that the extractive compounds obtained from black locust heartwood were able to increase the native durability of European beech from class 5 (i.e. not durable with an average mass loss of 43.6 %) to class 3 (i.e. moderately durable with an average mass loss of 12.7 %). The final Paper VII shows following results. After impregnation with residual liquids and leaching, high amounts of TT (thermal treatment) and HTC (hydrothermal carbonisation) solution were washed out, whereas Pyrolysis liquids stayed with 25 % to 40 % remaining in the wood. Volumetric swelling in 65 % relative humidity at 20 °C was reduced from 6.5 % in untreated poplar to 5 % in impregnated samples with process residues of thermal treatment using 180 °C or 200 °C. The processes using HTC liquids from Miscanthus sp. (Misc.) or Sawdust showed reduction to 3-3.5 % and Pyrolysis liquid treatment to 2.5 %. After exposure to fungi, the mass loss of untreated Beech (30-35 %) and Poplar (40-50 %) was reduced to 2 % in case of Pyrolysis- and 4 % in case of TT-treatment.
|
guest ::
