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Dissociation behaviour of natural biocolloids
Karbanová, Kateřina ; Sedláček, Petr (referee) ; Klučáková, Martina (advisor)
This diploma thesis is focused on the study of dissociation behaviour of natural biocolloids, namely humic acids and fulvic acids. Humic and fulvic acids are natural, heterogeneous, high molecular weight substances which behave as weakly acidic polyelectrolytes and they have complex not exactly described structure. They are formed by biochemical transformations of organic residues (mainly plants). They are part of the soil, water, peat, sediments and coal. Solubility of humic acids is affected by pH value. The higher the pH value is the higher the solubility is. Fulvic acids are soluble in whole range of pH values. The aim of this diploma thesis is to determine the dissociation constant for the five kinds of humic acids and four kinds of fulvic acids, which have been isolated from various natural sources. These samples were purchased from IHSS. Dissociation constants were determined by the conductometric method and a combination of measurment pH and the content of acidic functional groups in Na2SO4. UV-VIS spectrophotometry method was used to characterize the quality of humic acids and fulvic acids.
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Connection between the solubility and the mutagenicity of nitrobenzanthrones in water and organic solvents
Řeboun, Martin ; Martínek, Václav (advisor) ; Hudeček, Jiří (referee)
2-Nitrobenzanthron (2-NBA) and 3-nitrobenzanthron (3-NBA) are pollutants widely occurring in the environment. The main sources of benzanthrones are combustion products (i.e. diesel exhausts, wood and cigarette smoke ...). 3-NBA is proven mutagen and carcinogen for bacteria and mammals and it is probably mutagenic also to humans. Nitronbezanthrones can form covalent adducts with purine bases in DNA after their metabolic activation. Genotoxic properties of 2-NBA are lover by 3-4 orders of magnitudes in comparison to 2-NBA, large difference in the solubility, and therefore also the difference in their bioavailability, of these isomers can be among the factors explaining this phenomenon. One of our goals was to determine the solubility of 3-NBA and 2-NBA in water and in methanol. The second objective was to determine the extinction coefficients for their solutions in water and methanol. Two different methods were employed to determine the solubility of 3-NBA and 2-NBA. The first method was based on stepwise adding of the stock solution of 3-/2-NBA in dimethylsulfoxide to excessive volume of water and simultaneous spectrophotometric verification of the Lambert-Beer law. Additional experiments confirmed the solubility of 3-/2- NBA utilizing spectrophotometric determination of 3-/2-NBA concentration in...
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Bioinformatics Tool for Prediction of Protein Solubility
Hronský, Patrik ; Burgetová, Ivana (referee) ; Martínek, Tomáš (advisor)
This master's thesis addresses the solubility of recombinant proteins and its prediction. It describes the subject of protein synthesis, as well as the process of recombinant protein creation. Recombinant protein synthesis is of great importance for example to pharmacologic industry. This synthesis is not a simple task and it does not always produce viable proteins. Protein solubility is an important factor, determining the viability of the resulting proteins. It is of course favourable for companies, that take part in recombinant protein synthesis, to focus their effort and their resources on proteins, that will be viable in the end. In this regard, bioinformatics is of great help, as it is capable, with the help of machine learning, of predicting the solubility of proteins, for example based on their sequences. This thesis introduces the reader to the basic principles of machine learning and presents several machine learning methods, used in the field of protein solubility prediction. It deals with the definition of a dataset, which is later used to test selected predictors, as well as to train the ensemble predictor, which is the main focus of this thesis. It also focuses on several specific protein solubility predictors and explains the basic principles upon which they are built, as well as the results of their testing. In the end, it presents the ensemble predictor of protein solubility.
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Dissociation behaviour of humic acids
Karbanová, Kateřina ; Kratochvílová, Romana (referee) ; Klučáková, Martina (advisor)
Humic acids are substances of natural origin and form the finest part of humic substances. They are formed by biochemical transformations of organic residues (mainly plants). They act as a weakly acidic polyelectrolytes with not exactly described structure. Their solubility is affected by pH value. The higher the pH value is the higher the solubility is. They are almost insoluble in acids. Bachelor thesis deals with the study of the dissociation behaviour of humic acids. Dissociation constant of humic acids is determined by three different methods – conductometric, spectrophotometric and combination of measurment pH and the content of acidic functional groups in Na2SO4. On the basis of results the methods are compared.
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Behaviour of humic acids in aqueous solutions
Čechová, Eva ; Barančíková, Gabriela (referee) ; Klučáková, Martina (advisor)
Tato práce se zabývá chováním huminových kyselin ve vodných roztocích a to především jejich disociací a rozpustností. Disociace huminových kyselin byla studovaná jejich částečným rozpuštěním ve vodě a v roztocích solí o různých iontových silách. Analyzované huminové kyseliny pocházely jak z lignitických tak i půdních zdrojů a jedna z nich byla upravena plazmatem. Metodami použitými při experimentech byla potenciometrie, konduktomerie a UV/VIS spektroskopie. Podle Henderson-Hasselbalchovy závislosti byly vypočítány zdánlivé disociační konstanty. Dále byly určeny zdánlivé aktivitní koeficienty kyselých funkčních skupin. Poté byla studovaná rozpustnost huminových kyselin ve vodných roztocích solí. Byly sestrojeny závislosti pH hodnot, vodivostí a absorbancí jak na obsahu huminových kyselin ve vzorku tak na iontové síle roztoku. Studována byla také kinetika disociace huminových kyselin. Získaná data byla srovnána s navrženou hypotézou předpokládající několikakrokový mechanismus disociace huminových kyselin. Chovaní všech vzorků huminových kyselin odpovídalo navrženému mechanismu. Bylo potvrzeno, že stupeň disociace huminových kyselin ve vodných roztocích klesá s rostoucím obsahem huminové kyseliny stejně tak jako ve vodných roztocích solí s rostoucí iontovou silou.
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Fractionation of humic acids isolated from lignite
Moťka, Pavel ; Barančíková, Gabriela (referee) ; Klučáková, Martina (advisor)
The diploma thesis deals with lignitic humic acids. Bibliographic search can be divided into three parts. The aim of the first part is characterization of humic substances, presence, composition, structure and exploitation especially of humic acids. The second part describes a division of heterogeneous mixture of humic acids into closed fractions with more specific properties. The final part is a study of solubility of humic acids. The experimental part of the diploma thesis is structured similarly. In this work, a gradual fractionation with pH is used. Obtained fractions were characterized by UV/VIS and FT-IR spectroscopy. We assessed the portion of ash and carboxyl groups have been identified. Subsequently, all fractions extracted by gradual fractionation as well as some soluble fractions obtained by direct fractionation have been analyzed in view of solubility and their behaviour in water environment. Both used methods were compared.
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Determination of content of humic acids in solutions chronopotentiometrically
Viktorinová, Jana ; Kislinger, Jiří (referee) ; Klučáková, Martina (advisor)
Humic acids are part of humic substances, which are substances of natural origin occurring in soil, peats, sediments and young coal. These substances are mixture of compounds with different molecular weight and structures. Humic acids are only partially soluble in aqueous solutions and their solubility is growing up with icreasing pH value. Bachelor thesis uses method of chronopotentiometric titration, which has not been used yet for humic research. This bachelor thesis is trying to check possibility of exercise this method for assessment concentration of soluble humic acid. Especially trace amounts of analyt are measured by this method. Results obtained by chronopotentiometric titration are compared with results in common used method as UV/VIS spetctromerty and potentiometry.
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Solubility and dissociation of humic acids
Kratochvílová, Romana ; Jaroslav,, Záhora (referee) ; Klučáková, Martina (advisor)
The behaviour of humic acids in aqueous solutions is closely connected to the content of acid functional groups and their dissociation abilities. The titration methods are the most often used for the research of acid-basic characteristics of humic acids, their results should lead to the determination of the content of functional groups and their pKa. However the determined values depend on many factors including the titration speed. The aim of this bachelor’s thesis is to verify the possibility of UV/VIS spectrophotometry´s use as alternative method for the determination of pKa of humic acids and to compare the gained results with so far used method according to Henderson-Hasselbach. The principle of newly used spectrophotometry method is the preparation of humic acids solutions in three different media with different pH values. Acid groups of humic acids are practically completely dissociated in intensely basic environment and the measured absorbance is caused by anion of „humate“. On the contrary their dissociation in acid environment is suppressed so much that we measure the absorbance of non-dissociated molecules of humic acids. It was found out that after the modification it was possible to use the spectrophotometry method for the determination of pKa of these substances, while the use of method was verified within the three different samples of humic acids. The optimal ratio humic acids – water and the extent of wavelength for measuring UV/VIS spectra were determined. It was proved that the values of pKa determinated by these methods better describe the real dissociation behaviour of humic acids in water than traditional Henderson-Hasselbach method. The UV/VIS spectra gained in combination with the results of pH measuring and the conductivity next showed the differences in the behaviour of differently prepared samples of humic acids.
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Solubility of polypropylene in hydrocarbon solvents
Urbánková, Radka ; Kučera, Jaroslav (referee) ; Kratochvíla, Jan (advisor)
Polypropylene, on a mass-scale produced polyolefin, shows an excellent combination of end-use properties, eco-friendliness, easy recyclability, and a good processability by different technologies. Key structural parameters of polypropylene are its stereoregularity, molecular weight, and its distribution. A theoretical part of this work compiles a bibliographic search and an experimental part deals with extraction and solubility of polypropylene powder prepared on a highly active Ziegler-Natta polymerization catalyst. Extractions at a boiling point temperature of solvents (pentane - hexane - cyclohexane - hex-1-ene - benzene - heptane - octane - ethylbenzene) resulted in a progressive increase of extracted portions with temperature of extraction. Solvents used within this work were characterised by their physical properties, and steric and electronic parameters such as molecular weight, density, boiling point temperature, dipole moment, refractive index, and Hildebrand´s solubility parameter. Extraction PP at a constant temperature 36°C (boiling point of pentane) at a saturated vapour pressure in a series of hydrocarbon solvents (pentane – hexane – heptane – octane) resulted in practically the same results. Boiling octane extractable fraction at a temperature 36°C was nearly 100 % higher than fractions extracted by the other solvents. The origin of this phenomenon has not been revealed. Polypropylene solubility was determined by a complete dissolving the sample at 140°C in a series of aliphatic and aromatic solvents (pentane - hexane - cyclohexane - hex-1-ene - benzene - heptane - octane - toluene - ethylbenzene - o-xylene - m-xylene - p-xylene - decalin - chlorbenzene - 1,2-dichlorbenzene), followed by cooling the solution down to a laboratory temperature, and separating a soluble fraction, and an insoluble one. The stereoregularity of soluble fractions was characterised by a 13C NMR method, the crystallinity by a DSC method, and a molecular weight distribution by a GPC method. As a result, polypropylene solubility decreases with increasing the Hildebrand solubility parameter of the solvent that corresponds with theoretical expectations. Moreover, PP solubility correlates strongly with a refractive index, and a density of solvent.
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