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Desacetilação assistida por irradiação de ultrassom de alta intensidade aplicada a quitinas extraídas de gládios de lulas / Ultrasound-assisted deacetylation applied to extracted chitins of squid pensVirgínia de Alencar Muniz Gonzaga 10 December 2012 (has links)
Neste trabalho, amostras de beta-quitina extraída de gládios de lulas foram submetidas ao processo DAIUS, desacetilação assistida por irradiação de ultrassom de alta intensidade, visando à produção de quitosanas extensivamente desacetiladas e de massa molar elevada. Para isso, os parâmetros do processo, a saber, diâmetro do reator, tempo de pulsação da irradiação do ultrassom e tempo de pré-condicionamento visando o intumescimento das partículas de beta-quitina, foram variados utilizando um planejamento fatorial fracionário (23-1). Desse planejamento resultou a execução de quatro experimentos e a triplicata do ponto central. A beta-quitina de partida e as quitosanas obtidas foram caracterizadas por espectroscopia de RMN 1H, espectroscopia da região do infravermelho, difração de raios X, viscosimetria capilar, microscopia eletrônica de varredura e termogravimetria. O parâmetro de acetilação (PA) das quitosanas obtidas foi determinado a partir dos espectros de RMN 1H de modo a permitir a avaliação do tipo de distribuição das unidades GlcNAc e GlcN predominante nas cadeias. As quitosanas apresentaram parâmetro de acetilação variando no intervalo 0,61<PA<0,82, indicando o predomínio da distribuição randômica das unidades GlcNAc e GlcN. A determinação da solubilidade das quitosanas foi baseada na turbidez de suas soluções, sendo todas solúveis em pH < 5, exceto a amostra QT2 que foi insolúvel. A beta-quitina apresentou maior estabilidade térmica em comparação com as quitosanas, devido à maior porcentagem de unidades GlcNAc nas suas cadeias. As características morfológicas da beta-quitina e das quitosanas foram determinadas pelo emprego da microscopia eletrônica de varredura, foi observado que as partículas das quitosanas apresentaram certa rugosidade aparente devido à ocorrência de um acentuado processo de descamação da superfície do polímero. A partir dos espectros no infravermelho foi possível identificar e diferenciar as bandas características, tanto da beta-quitina quanto das quitosanas. Os valores de grau médio de acetilação e de massa molar viscosimétrica média das amostras de quitosana variaram nos intervalos 42%<<span style=\"text-decoration: overline\">GA<62% e 1,25x105g.mol-1<<span style=\"text-decoration: overline\">Mv<2,93x105g.mol-1, respectivamente. Esses resultados revelam que o processo DAIUS foi eficiente na conversão de beta-quitina em quitosana, e que foram produzidas quitosanas com elevada massa molar viscosimétrica média, entretanto o intervalo de variação dos parâmetros do processo não resultou em variação importante do grau médio de acetilação das quitosanas produzidas. / In this project, β-chitin samples extracted from squid pens were submitted to the USAD, ultrasound assisted deacetylation process aiming the production of extensively deactylated high molar mass chitosans. For that process parameters, as, diameter of the reactor, ultrasound irradiation pulsing time and pre-conditioning time seeking the swelling of the β-chitin particles, they have been varied using a fractional factorial design (23-1). From this design resulted the performance of four experiments and the central point triplicate. The β-chitin pattern and the obtained chitosans were characterized by 1H NMR spectroscopy, infrared spectroscopy, X-ray diffraction, capillary viscometry, scanning electron microscopy and thermogravimetry. The parameter of acetylation (PA) of the obtained chitosans was determined from the 1H NMR spectra, allowing the assessment to the distribution pattern of GlcNAc and GlcN units predominant in the chains. The chitosans presented parameter of acetylation ranging as 0,61<PA<0,82, indicating the predominance of random distribution of GlcNAc and GlcN units. The determination of the chitosans solubility was based on the turbidity of its solutions, all being soluble in pH < 5, exept for QT2 sample that was insoluble. The β-chitin showed higher thermal stability in comparisson to the chitosans, probably due to the higher content of GlcNAc units in their chains. The morphological characteristics of β-chitin and chitosans were characterized by scanning electron microscopy, It was observed that the chitosans particles presented certain rugosity apparently due to the occurrence of a strong process of scaling of the polymer surface. From the infrared spectra it was possible to identify and to distinguish the characteristic bands either of the β-chitin as the chitosans. The values of the average degree of acetylation and viscosity average molar mass from the chitosans samples vary in the intervals 42%<<span style=\"text-decoration: overline\">GA<62% e 1,25x105g.mol-1<<span style=\"text-decoration: overline\">Mv<2,93x105g.mol-1, respectively. These outcomes reveal that the USAD process was effective converting β-chitin in chitosan and there were generated chitosans with high viscosity average molar mass, however the process parameters variation interval did not result in an important average degree of acetylation variation from the generated chitosans.
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Rheological characterization of Xanthan-guar mixtures in dilute solutionsKhouryieh, Hanna Anton Michael January 1900 (has links)
Doctor of Philosophy / Food Science Program / Fadi M. Aramouni / Thomas J. Herald / Dynamic viscoelastic and intrinsic viscosity properties of native xanthan, deacetylated xanthan, guar, and their mixtures in dilute solutions were investigated by using an oscillating capillary rheometer. Influence of mixing temperature, deacetylation, and salt concentration on xanthan conformation and interaction with guar were studied in order to provide additional evidence that can be used to elucidate the mechanism of the intermolecular interaction between the two biopolymers, and build up a more detailed rheological understanding of molecular interactions between xanthan and guar gum in dilute solutions.
Synergistic interaction was found at mixing temperatures of 25 and 80 °C, but a stronger synergistic interaction was observed at mixing temperature of 80 °C. The differences in viscosity and elasticity measurements between the two mixing temperatures could be attributed to the degree of disordering of xanthan. For both mixing temperatures, the relative viscosity and elasticity of xanthan and guar blends were higher than the relative viscosity and elasticity calculated for blends assuming no interaction, indicating that intermolecular binding occurred between galactomannans backbone and disordered segments of xanthan.
Deacetylated xanthan exhibited a stronger synergistic interaction with guar than native xanthan. The intrinsic viscosities of deacetylated xanthan-guar mixtures were higher than those calculated from the weight averages of the two individually, whereas the intrinsic viscosities of native xanthan-guar mixtures were lower than those calculated from weight averages of the two individually, demonstrating that intermolecular binding occurred between xanthan and guar gum.
Synergistic interaction for both native xanthan-guar mixtures and deacetylated xanthan-guar mixtures in the dilute regime was observed in water and 2 mM NaCl but not in 40 mM NaCl. The results suggest that intermolecular interaction has occurred between xanthan and guar mixtures in water and 2 mM NaCl, but may not occur in 40 mM NaCl and mutual incompatibility may take place. These results also suggest that degree of disordering of xanthan played a critical role in xanthan-guar interaction and may explain the differences in viscosity, elasticity, and intrinsic viscosity measurements between 2 and 40 mM NaCl, and hence, the intermolecular interaction occurred between the backbone of guar gum and the disordered segments of xanthan.
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Valproic Acid Leads to an Increase in ROS Generation by Inhibiting the Deacetylation of Mitochondrial SODLucas, Stephen Marc 03 August 2020 (has links)
Valproic Acid Promotes Acetylation of Superoxide Dismutase-2 During Neurogenesis. Valproic acid (VPA) is a known developmental toxicant associated with a high prevalence of neural tube defects (NTD). The mechanism of VPA-induced NTD is unclear, but oxidative stress may be implicated. To understand how embryotoxic oxidative stress may occur, we measured superoxide dismutase (SOD) activity following VPA treatment in the embryonic pluripotent P19 mouse carcinoma cell line. In undifferentiated P19 cultures treated with VPA (5 mM), dichlorofluorescein fluorescence increased 15% compared to untreated controls over 20 min, indicating a modest, yet statistically significant increase in ROS generation. Undifferentiated P19 cells were treated with VPA for 6 h, after which total SOD and mitochondrial SOD (SOD2) activities were measured. VPA treatment decreased total SOD activity by approximately 20% but SOD2 activity was undetectable; but this was not a consequence of changes to SOD (SOD1 or SOD2) protein concentrations. Interestingly, glutathione redox state increased from -262 mV to -245 mV after a 6 h treatment with VPA, indicating significant oxidation of the cellular redox environment. Measurement of mitochondrial superoxide levels showed an increase following VPA treatments. While it is unlikely that VPA works directly as an oxidant, these data suggest that VPA may promote oxidative stress through an alternative means, such as via the inhibition of SOD activity and thus, allow for an increase in ROS. Importantly, VPA is a known deacetylase inhibitor, and SOD2 function is regulated by acetylation. As such, we evaluated the acetylation state of SOD2 to determine potential disruption via acetylation. Treated undifferentiated P19 cells showed a significant increase in SOD2 acetylation. However, in fully differentiated P19-derived neurons, cells showed no such SOD2 acetylation. Additionally, pretreatment with dithiole-3-thione (D3T), a Nrf2 activator of the antioxidant response, attenuated VPA-induced mitochondrial ROS production and SOD2 acetylation and improved SOD2 activity, suggesting Nrf2 as a potential means to reduce VPA-mediated oxidative stress. To evaluate the effects in the embryo proper, gestational day 8 mouse embryos were treated with VPA in culture for 6 h. Similar to P19 cells, VPA-treated neurulating embryos showed significant SOD2 acetylation and a concomitant decrease in total SOD activity. These data support a similar consequence of VPA-induced oxidative stress in embryos as is demonstrated in our cellular model. Since no SOD2 acetylation is observed in differentiated neurons and VPAinduced SOD2 acetylation occurs more prevalently in undifferentiated/differentiating cells, these data purport means by which VPA preferentially induces oxidative stress in developing systems.
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Diazonium (Perfluoroalkyl) Arylsulfonylimide Zwitterionic Monomer Analogues: Effective Synthesis and Thermal StabilityMei, Hua, Nworie, Chimaroke, Abban, Grace, Alayyaf, Abdulmajeed, MacCloud, Rebecca 09 February 2016 (has links)
It is very promising to introduce diazonium moiety into Nafion monomer based Diazonium (Perfluoroalkyl) Arylsufonylimide (PFSI) monomers for further polymerization and chemical grafting onto carbon electrodes as innovative electrolyte materials in the Proton Exchange Membrane (PEM) fuel cells. The PFSI polymers, more proton conductive and stable at high temperatures, can dramatically increase the stability and lifetime of the PEM fuel cells, compared to widely used perfluorosulfuric acid (PFSA) polymers. This paper presents such a straightforward methodology to optimally construct a new nafion based diazonium PFSI monomer analogue, 2-diazonium 4-(trifluoromethyl) perfluoro-3, 6-dioxa-4-methyl-7-octene benzenesulfonylimide II. New approaches have been investigated to dramatically increase the percent yield for another monomer I, 4-diazonium perfluoro-3, 6-dioxa-4-methyl-7-octene benzenesulfonylimide. The thermal stability of the two monomer analogues then have been measured and compared. Another monomer analogue, 4-diazonium-3-fluoro perfluoro-3, 6-dioxa-4-methyl-7-octene benzenesulfonylimide III, has been attempted and discussed.
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Deacetylated Hyaluronan : Exploration of deacetylation techniques for hyaluronan (oligo and polysaccharides)Mardini, Sima, Björk, Hanna, Möller, Marcus, Lagergren, Carl, Samuelsson, Oscar January 2023 (has links)
Hyaluronic acid is an organic polysaccharide with a wide range of uses in medical and cosmetic industries due to its physiological properties. Crosslinked hyaluronic acid is a commonly used filler agent because of its water retention capabilities. N-deacetylation can be performed to enable new derivatives of hyaluronic acid. Both chemical and enzymatical approaches were investigated in this literature study to find methods retaining a high molecular weight product. Chemical N-deacetylation of hyaluronic acid has significant challenges with being treated by acid or base while both preventing degradation and maintaining its molecular weight. The method that seems the most promising is treating hyaluronic acid with hydroxylamine. Another method is enzymatic N-deacetylation. It was found that an enzyme N-deacetylated hyaluronic acid in female breast skin from 69-year-olds and above. The isolated enzyme had molecular weights ranging from 63 kDa to 79 kDa. Another enzyme that was produced recombinantly proved to be efficient since it retained high molecular weight and had a degree of deacetylation of 10.1 %. Today there exists only a few methods for crosslinking deacetylated hyaluronic acid. However, for chitosan, there are multiple methods available for crosslinking. Since it uses similar reactions that could be applicable to that of deacetylated hyaluronic acid. Reacetylation of the free amino groups has proven to be possible after crosslinking with a simple and cheap method resulting in an almost complete reacetylation. NMR proved to be an adequate method for analyzing the degree of deacetylation and higher-order structures. HPLC-UV spectroscopy may be used to increase the credibility of the analysis.
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Produção de etanol a partir da palha de arroz por sacarificação e fermentação simultânea empregando um reator agitado não convencional. / Ethanol production from rice straw by simultaneous saccharification and fermentation employing a non-conventional stirred reactorCastro, Rafael Cunha de Assis 03 February 2017 (has links)
O presente trabalho teve como principal objetivo estudar o processo de producao de etanol por sacarificacao e fermentacao simultanea (SSF) a partir da palha de arroz em um reator agitado nao convencional, denominado Moinho de Bolas Vertical (MBV). Foi também objetivo deste trabalho realizar uma avaliacao tecnico-economica a partir dos resultados experimentais alcancados durante o processamento da biomassa, aplicando o conceito de biorrefinaria. Inicialmente, foi avaliada uma sequencia de pre-tratamentos da palha de arroz que consistiu de uma etapa de desacetilacao alcalina, seguido de hidrolise com acido diluido. Os efeitos destes pre-tratamentos foram analisados com base nas modificacoes estruturais da palha de arroz e no rendimento de conversao de celulose (RCC) em cada solido obtido. Com base nos resultados, foram definidas as condicoes otimas para a etapa de desacetilacao (80 mg de NaOH/g de palha in natura, 70 °C, 45 min), de hidrolise acida (100 mg de H2SO4/g de palha desacetilada, 121 °C, 85 min) e carga de enzimas (21,5FPU e 26,5 UI de ?-glicosidase/g de celulose). Nestas condicoes, foram conduzidos experimentos em reator MBV visando avaliar o efeito das da velocidade de agitacao (100 a 200 rpm), numero de esferas (0 a 30) e temperatura (40 a 46 °C) sobre o RCC na sacarificacao da celulignina desacetilada e sobre a eficiencia da fermentacao por Kluyveromyces marxianus NRRL Y- 6860 em meio semissintetico. Apos definicao das variaveis significativas aos processos, foram realizados experimentos em reator MBV na configuracao de SSF em batelada simples e alimentada. Em batelada simples com 8% de solidos, foi obtida uma concentracao de etanol de 23,1 g/L, com eficiencia (?) de 89,8% e produtividade volumetrica (QP) de 1,6 g/L.h, nas seguintes condicoes operacionais: 200 rpm, 18 esferas e 41,5 °C. No entanto, com o aumento do teor de solidos para 24%, ambos os parametros (??e QP) foram reduzidos em 50%. Visando melhorar os parametros do processo com 24% de solidos, foram realizados ensaios em batelada alimentada e na melhor estrategia de alimentacao do substrato foi produzido 52,3 g/L de etanol (?= 67,5% e QP = 1,1 g/L.h). As fracoes ricas em lignina geradas a partir do licor alcalino e do residuo de fermentacao da batelada alimentada foram caracterizadas fisico-quimicamente, e analisadas quanto ao potencial antioxidante. A partir dos resultados, foram sugeridas possiveis aplicacoes para estes dois residuos ricos em lignina. Finalmente, de posse do balanco de massa de cada etapa do processamento da palha de arroz, foi realizada uma analise tecnico-economica empregando o software SuperPro Designer. As simulações mostraram que, para todos os cenarios avaliados, a etapa de pre-tratamento acido foi a de maior impacto sobre os custos operacionais, seguido pelas etapas de fermentacao (xilose e glicose). Ficou demonstrado ainda que, a conversao de xilose em xilitol proporcionou um melhor retorno financeiro do que a conversao desta pentose em etanol. Para a viabilidade economica da presente proposta de biorrefinaria, alem da diversificacao dos produtos obtidos a partir das fracoes acucaradas, e de fundamental importancia explorar as potencialidades dos residuos ricos em lignina. / The aim of this work was to study the ethanol production by simultaneous saccharification and fermentation (SSF) from rice straw in a non-conventional agitated reactor, called Vertical Ball Mill (VBM). It was also objective of this study to perform a techno-economic analysis from the experimental results achieved during the biomass processing, using the biorefinery concept. Initially, the rice straw was submitted to a sequential pretreatment consisting of an alkaline step (deacetylation) followed by dilute acid hydrolysis. The pretreatment effects were evaluated based on rice straw\'s structural modifications and regarding cellulose conversion (CC) from each obtained solid. Based on the results were defined the best conditions for the deacetylation step (80 mg NaOH/g of rice straw in natura, 70 °C, 45 min), acid hydrolysis (100 mg H2SO4/g deacetylated straw 121 °C, 85 min) and enzyme loading (21.5 FPU and 26.5 IU ?-glucosidase/g cellulose). Under these conditions, assays were carried out in VBM reactor to evaluate the effect of stirring speed (100-200 rpm), number of spheres (0-30) and temperature (40-46°C) on saccharification of deacetylated cellulignin and fermentation efficiency by Kluyveromyces marxianus NRRL Y-6860 in semisynthetic media. After defining the significant variables, experiments were carried out in VBM reactor by SSF configuration in batch and fed-batch operational modes. In batch SSF at 8% solids, was obtained an ethanol concentration of 23.1 g/L, with a process efficiency (?) of 89.8%, and volumetric productivity (QP) of 1.6 g /L.h, in the following operating conditions: 200 rpm, 18 spheres and 41.5 °C. However, by increasing solids content to 24%, both parameters (? and QP) were decreased by 50%. In order to improve the process parameters to 24% solids, fed-batch experiments were performed. In the best substrate feeding policy was produced 52.3 g/L ethanol (? = 67,5%) in 48-h process (QP = 1.1 g/L.h). The lignin-rich fractions from the alkaline liquor and from fed-batch fermentation residue were characterized regarding its chemical composition and physical properties and analyzed for antioxidant activity. Based on these results were suggested possible applications for both lignin-rich residues. Finally, considering the mass balance from all rice straw processing steps, a techno-economic analysis was assessed using SuperPro Designer software. The simulation procedures have indicated that, for all evaluated scenarios, the acid pretreatment step had the highest impact on operating costs, followed by the fermentation steps (xylose and glucose). It was also shown that xylose conversion into xylitol provided a better payback rather than its conversion into ethanol. Therefore, to attain a viable and profitable process for this type of rice straw based biorefinery, in addition to the diversification of products obtained from the sugary fractions, it is crucial to explore the potential of lignin-rich streams.
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Extraction of chitosan from Fungal cell wall by Sulfuric acid Studying the effect of Deacetylation degree and temperature on recovery chitosanGholizadeh Aghdam, Mehdi January 2010 (has links)
The goal of this project is extraction of chitosan optimally by surveys of temperature changesalong with 1% Sulfuric acid utilization. Microbial chitosan is isolated as a bio-componentfrom cell wall of two kinds of Zygomycetes by some extraction methods. This projectcompares ability of two type Fungi (R. pulusilus and M.indicus) from Zygomycets forproduction of chitosan.To extract of chitosan is a combinational method with 40 %( w/w) Hydroxyl sodium for celldisruption and diluted Sulfuric acid (1% w/v) for chitosan extraction from cell wall as majorchemical components. 40% NaOH is used to get different degrees of deacetylation (DD) fromchitin for chitosan. In addition, it is examined 1% Sulfuric acid in a combination oftemperature factor changes. It is needed dialysis for chitosan purification from bondedphosphate groups. Standard curves of acetic acid experiences for DD and water phosphatedetermination were accomplished.It has resulted if degree of deacetylated chitin is about 50%; it has an average lost more than50% in 1% (v/v) Sulfuric acid, hence less recovery as a no privilege that it can be relapsed byacetone in chitosan solution. Factor of temperate in same times shows important effect onextraction yield of chitosan by 1% Sulfuric acid. Extracted chitosan in 120℃ has DD about50%. Absolutely, its solubility will be more and it needs to an intricate solution for separationof chitosan from phosphate bonds as a major impurity by dialysis, but in 90℃, DD of chitosanis more with less solubility in water.Between two Fungi, in experienced temperatures, hence, R. pulusilus has more recovery about0.87/AIM (g/g) in 90℃, which have more much DD than 50%, and M.indicus has 0.79/AIM(g/g) in 120℃ that it has DD about 50%.
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Investigating the inhibitor and substrate diversity of the JmjC histone demethylasesSchiller, Rachel Shamo January 2016 (has links)
Epigenetic control of gene expression by histone post-translational modifications (PTMs) is a complex process regulated by proteins that can 'read', 'write' or 'erase' these PTMs. The histone lysine demethylase (KDM) family of epigenetic enzymes remove methyl modifications from lysines on histone tails. The Jumonji C domain (JmjC) family is the largest family of KDMs. Investigating the scope and mechanisms of the JmjC KDMs is of interest for understanding the diverse functions of the JmjC KDMs in vivo, as well as for the application of the basic science to medicinal chemistry design. The work described in this thesis aimed to biochemically investigate the inhibitor and substrate diversity of the JmjC KDMs, it led to the identification of new inhibitors and substrates and revealed a potential combinatorial dependence between adjacent histone PTMs. Structure-activity relationship studies gave rise to an n-octyl ester form of IOX1 with improved cellular potency and selectivity towards the KDM4 subfamily. This compound should find utility as a basis for the development of JmjC inhibitors and as a tool compound for biological studies. The rest of this thesis focused on the biochemical investigations of potential substrates and inhibitors for KDM3A, a JmjC demethylase with varied physiological functions. Kinetic characterisation of reported KDM3A substrates was used as the basis for evaluations of novel substrates and inhibitors. Further studies found TCA cycle intermediates to be moderate co-substrate competitive inhibitors of KDM3A. Biochemical investigations were carried out to study potential protein-protein interactions of KDM3A with intraflagellar transport proteins (IFTs), non-histone proteins involved in the formation of sperm flagellum. Work then addressed the exploration of novel in vitro substrates for KDM3 (KDM3A and JMJD1C) mediated catalysis, including: methylated arginines, lysine analogues, acetylated and formylated lysines. KDM3A, and other JmjC KDMs, were found to catalyse novel arginine demethylation reaction in vitro. Knowledge gained from studies with unnatural lysine analogues was utilised to search for additional novel PTM substrates for KDM3A. These results constitute the first evidence of JmjC KDM catalysed hydroxylation of an Nε-acetyllysine residue. The H3 K4me3 position seems to be required for acetyllysine substrate recognition, implying a combinatorial effect between PTMs. Preliminary results provide evidence that JMJD1C, a KDM3 protein previously reported to be inactive, may catalyse deacetylation in vitro. An additional novel reaction, observed with both KDM3A and JMJD1C, is deformylation of N<sup>ε</sup>-formyllysine residues on histone H3 fragment peptides. Interestingly, H3 K4 methylation was also observed to enhance the apparent deformylation of both KDM3A and JMJD1C catalysed reactions. Overall, findings in this thesis suggest that the catalytic activity of JmjC KDMs extends beyond lysine demethylation. In a cellular context, members of the KDM3 subfamily might provide a regulatory link between methylation and acylation marks. Such a link will further highlight the complex relationships between histone PTMs and the epigenetic enzymes that regulate them. The observed dependency of H3 K9 catalysis on H3 K4 methylation adds another layer of complexity to the epigenetic regulation by histone PTMs.
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Chitosan-glukanový komplex izolovaný ze Schizophyllum commune. / The chitosan-glucan complex isolated from Schizophyllum communeKrčmář, Martin January 2011 (has links)
Chitosan-glucan complex is fungal origin copolymer that finds application in medicine and cosmetics. Traditionally mycelium of Aspergillus and Penicillium is considered as industrial chitosan-glucan complex source, though utilization of Micromycetes in biotechnological productions is sometimes undesirable. The aim of the work was to study the possibility of Basidiomycete Schizophyllum commune submerged cultivation for industrial scale chitosan-glucan complex production use. Within the work there was studied effect of cultivation conditions (type and concentration of carbon sources in nutrient medium, ratio of carbon source to nitrogen source, medium initial pH and aeration intensity) on Sch. commune #127 mycelium growth, chitosan-glucan complex formation and exopolysaccharide synthesis. As the result, the method for chitosan-glucan complex production increase and exopolysaccharide synthesis suppression was suggested. Chitosan-glucan complex from Sch. commune #127 submerged mycelium was separated by successive alkali and acid treatments. Effects of alkali concentration and application technique, and type of acid on physical and chemical properties of chitosan-glucan complex were described. Analytical methods for in process control and final product characteristics were suggested.
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Chemické modifikace hydrogelů z přírodního polysacharidu / Chemical modifications of hydrogels from natural polysaccharidePoštulková, Hana January 2014 (has links)
V teoretické části práce by shrnuty chemické a fyzikální vlastnosti, chemická struktura a využití přírodního polysacharidu gum karaya. Hlavním cíle diplomové práce byla alkalická modifikace původní nerozpustné gum karayi na rozpustný produkt, který může být v budoucnu využit pro další aplikace například v medicíně. Nerozpustnost gum karayi je způsobena přítomností acetylových skupin a vícemocných iontů ve struktuře polysacharidu. Byly zkoumány optimální podmínky pro modifikační proces. Pro modifikaci byl použit hydroxid sodný, draselný nebo amonný a čas modifikace od 1 minuty po 24 hodin pro roztok originální gum karayi s koncentrací od 0,1 do 3 %. Pro určení chemického složení originálního a modifikovaných vzorků byla využita FTIR. Bylo prokázáno, že vzorky A2, B1 - 7, C1 - 8 a E1 - 2 byly zcela deacetylovány, protože pás pro acetylovou skupinu nebyl v FTIR spektrech pozorován. Odstranění acetylových skupin alkalickou modifikací bylo taktéž potvrzeno 13C CP MAS NMR. Pomocí XRD byl prokázán amorfní charakter originálního vzorku. Množství vlhkosti a teplotní stabilita vzorků byly zkoumána pomocí TGA. Bylo zjištěno, že termální stability originální gum karayi je vyšší než u modifikovaných vzorků. Termální stabilita modifikovaných vzorků byla ovlivněna reakčními parametry. Entalpické změny vzorků byly studovány pomocí DSC, nicméně nebyly pozorovány žádné významné rozdíly mezi modifikovanými vzorky a originální gum karayou. Prvkové složení bylo určeno pomocí ICP-OES a byla potvrzena přítomnost vápníku, draslíku a hořčíku ve struktuře polysacharidu. Molekulová hmotnost modifikovaných vzorků byla měřena pomocí GPC a byla stanovena na 8 milionů g·mol-1. Reologické měření roztoků gum karayi bylo provedeno pro určení lineární viskoelastické oblasti. Dále byl sledován efekt NaCl na viskozitu originálního vzorku. Viskozita klesala s vyšším množstvím NaCl. Pokles viskozity originálního vzorku je způsoben výměnou vápenatých iontů za sodné, což vede k uvolnění fyzikálně vázané struktury a tím k vyšší rozpustnosti vzorku ve vodě.
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