National Repository of Grey Literature 6 records found  Search took 0.01 seconds. 
Hyaluronan-amino acids interactions
Jugl, Adam ; Maršálek, Roman (referee) ; Mráček, Aleš (referee) ; Pekař, Miloslav (advisor)
The presented dissertation focuses on non-covalent interactions of hyaluronan of different molecular weights (9–1540 kDa) with basic (oligo)-amino acids (especially arginine) and the antimicrobial peptide cecropin B. High-resolution ultrasonic spectroscopy (HR-US), isothermal titration calorimetry (ITC) and potentiometric titration techniques were chosen to investigate the interactions. The thesis focuses on the characterization of interactions, especially with respect to the used molecular weight of interacting polymers and the ionic strength of the environment. Whether interactions occur or not was determined primarily by the length of the arginine oligomer chain. For monomeric amino acids, the interactions were investigated mainly by potentiometric titrations. Interactions were observable from arginine oligomers with eight monomer units. The molecular weight of hyaluronan mainly affected the intensity of the interactions. The transition between the individual conformations of hyaluronan (rod and random coil) was especially significant. Investigation of interactions was performed in water, in solutions with different concentrations of sodium chloride and in PBS. The sufficiently high ionic strength of the solution was able to suppress the interactions in water between the oligomers of arginine and hyaluronan. The basic antimicrobial peptide cecropin B has been shown to interact with hyaluronan in water but not in PBS. Based on these results, it was possible to conclude that the hyaluronan-cecropin B system would be particularly suitable for topical applications.
Influence of Solvent on Deformation Behavior of Hydrogels
Kulovaná, Eva ; Bartlová, Milada (referee) ; Mráček, Aleš (referee) ; Žídek, Jan (advisor)
The thesis deals with molecular dynamic simulation of the influence of water on the deformation of hydrogels. Hydrogels are model materials formed from macromolecular networks solvated with water. It was found that water can form bridges between macromolecules that take the form of temporary ionic crosslinks. These bridges affect the behavior of the network during deformation. Water bridges are water molecules that have a limited radius of motion in the space between two macromolecules. The concentration of the water bridges was regulated by a partial charge on the macromolecular chain in the organic network. Bridges are a type of interaction that is relatively strong but significantly delocalized. It is not possible to dissociate the water bridge, after dissociation it will be re-created in another place in a short time. The influence of water bridges was compared with other types of network crosslinks, especially covalent and physical bonds. Covalent crosslinks are modeled as a simple binding interaction between two macromolecules. They are undissociable and are local throughout the simulation. Physical bonds are modeled as micelles, where hydrophobic groups form the core and hydrophilic groups form the micelle shell. Physical bonds have the nature of dissociable bonds that are local. Different types of crosslinks have different effects on deformation properties. The deformation of a network containing a combination of two types of crosslinks was simulated: (i) physically-covalent, (ii) ionically-covalent, and (iii) physically-ionic networks and (iv) ternary physically-covalent-ion networks. For individual and combined networks, the behavior depending on simple networks was verified. The number of water bridges was fundamentally affected by the primary structure of the chains. When the PEG chain was replaced with hydrophobic polyoxymethylene (POM) or polyoxytrimethylene (POTM), their solvation and mechanical behavior deteriorated.
Preparation and characterization of thin barrier layers
Blahová, Lucie ; Mráček, Aleš (referee) ; Buršíková, Vilma (referee) ; Krčma, František (advisor)
Combinations of different acrylic resins and microcrystalline waxes are most often used for the conservation and preservation of metallic archaeological artefacts these days. However, their properties are not sufficient and satisfactory in many ways. Therefore, the aim of this doctoral thesis is to develop a conservation system which will draw on the new knowledge gained in the field of advanced materials and technologies during last years. A conservation coating based on a thin barrier film appears the most promising. The conservation coating must fulfil particularly following rather contradictory requirements: good barrier function against oxygen, humidity and other corrosive agents; transparency because of colour appearance preservation; long term stability and easy removability; possibility to apply to more objects at the same time and reasonable financial requirements of a deposition process. Parylene C polymer was chosen as suitable material for this purpose. It was prepared via modified chemical vapour deposition. Parylene removability was ensured through the soluble interlayer made of Laksil silicone-acrylic lacquer which was applied between the protected metallic object and the parylene thin film. Initially, the deposition process of Laksil/parylene bilayer was optimized, then its physical and chemical characteristics were determined and eventually, they were compared with the conventional conservation coating composed of Paraloid B72 acrylic resin and Revax microcrystalline wax. Regarding to the demands of the conservation coating, we were interested especially in barrier properties, optical properties, surface morphology and removability of Laksil/parylene bilayer. The most useful method for description of coating barrier properties was corrosion testing in which coated metallic samples were exposed to highly corrosive environment of salt spray (made of 50 g•l–1 brine), 100% humidity and temperature of 35 °C (ISO 9227). The Laksil/parylene bilayer showed excellent barrier properties; samples treated this way sustained unchanged in the corrosion chamber for almost three months. The surface roughness measured by profilometry and surface morphology scanned by SEM illustrated the synergy between Laksil and parylene layer which leads to the exceptional barrier and anticorrosion function of bilayer. The Laksil layer is able to flatten out rough surface of a substrate. Furthermore, it can toughen the item surface which is, in case of a number of archaeological findings, created by corrosion product layers with variable mechanical strength. Thereon deposited parylene film becomes smooth and defect free and can act as a good diffusion barrier. The colouristic measurements confirmed that the Laksil/parylene bilayer does not almost change the appearance of protected item, in terms of colour. The caused colour difference (ISO 11664-4) ranged around 1 which value is defined as “perceivable only for experienced observers”. The Laksil/parylene bilayer is removable thanks to the Laksil solubility in xylene. It is necessary to carefully scratch the outer parylene film to enable access of xylene solvent to the lacquer. The successful removal of Laksil/parylene bilayer was first confirmed by the EDX on metallic iron samples. Afterwards, the possibility of bilayer complete removal even from a corroded surface of the original artefact was proved by TGA. Thus the conservation treatment can be considered fully reversible.
Technology of monofilamentous fibers based on oxidized hyaluronic acid
Běťák, Jiří ; Mráček, Aleš (referee) ; Burgert, Ladislav (referee) ; Klučáková, Martina (advisor)
Předkládaná dizertační práce se zabývá vývojem technologie výroby nového typu biodegradabilních vláken na bázi oxidované kyseliny hyaluronové. V rámci práce je postupně představován vývoj jednotlivých jednotkových operací výroby, jejichž správné porozumění a schopnost jejich řízení jsou klíčové pro žádaný chod celé vícestupňové technologie. V rámci práce je představen nezbytný vývoj technologického zařízení, průběžně konstruovaného pro účely laboratorního testování a následně až po samotnou linku pro finální výrobu vláken, která byla realizována v roce 2015. V rámci dizertační práce jsou dále navrhovány možnosti dodatečné chemické úpravy vláken s ohledem na zvyšování jejich stability ve vlhkém prostředí. S ohledem na cílené aplikace vláken pro vnitřní chirurgické implantace, jsou v práci vlákna též hodnocena z hlediska jejich materiálové biokomaptibility (toxicity).
Utilization of Diffusive Techniques in Study on Reactivity of Biocolloids
Kalina, Michal ; Maršálek, Roman (referee) ; Mráček, Aleš (referee) ; Klučáková, Martina (advisor)
The main aim of this thesis is the utilization of simple diffusion techniques for the study on transport properties of copper ions in the systems containing humic acids with respect to the other parameters, which can affect the process (the structure of diffusion environment, the interactions between transported specie and diffusion matrices, selective blocking of binding sites of humic acids). The first part of experimental works was focused on characterization of studied materials (humic acids, humic sol and humic hydrogel). The main part of the thesis was dealing with the optimization of simple diffusion techniques, which were suitable for the study on transport of copper ions in matrices containing humic acids, taking into account the mutual interactions between studied components in the system. The obtained diffusion characteristics were compared to the data determined using sorption experiments. Consequently, the minor goal of the experimental works of this thesis was also the assessment of the influence of basic physico-chemical parameters of studied materials on transport phenomenon.

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