|
|
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.
|
|
|
Utilization of chronopotentiometric titration in humic research
Viktorinová, Jana ; Pospíšilová, Ľubica (referee) ; Klučáková, Martina (advisor)
Humic acids are natural substances belonging to the group of humic substances. They arise mainly decomposition of plant residues. They are contained in soils, peat, sediments, young coal, water and even in the air. Humic acids are only partially soluble in water with increasing pH increases their solubility. Diploma thesis focuses on the use of chronopotentiometric titration of humic research. This method is mainly used for the determination of trace concentrations of analytes. This work is focused on the determination of acidity by potentiometric titration and the determination of dissociation constants using chronopotentiometry with measurement of pH of prepared samples.
|
|
|
Investigation of acid-base and electrolytic properties of hyaluornan in aqueous solutions
Suchá, Šárka ; David, Jan (referee) ; Chytil, Martin (advisor)
This diploma thesis deals with acid-base and electrolytic behavior of hyaluronan solutions at different ionic strength. Acid-base behavior of hyaluronan was investigated by acid-base titrations which were carried out with two different methods, acid and alkaline acid-base titration. Dissociation constants at different ionic strength at zero degree of dissociation and at 50% degree of dissociation were evaluated from the results of acid-base titrations. Dissociation constants obtained from acid acid-base titrations have values between 3,0 and 3,6. Dissociation constants obtained from alkaline acid-base titrations are not very informative because their values are much higher than the expected values. The study of degradation of hyaluronan during acid-base titration was performed to complete study of acid-base behavior. Electrolytic behavior of hyaluronan solution was performed by conductometric titrations in three different environments.
|
|
|
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.
|
|
|
The electrochemical study of the degradation of the natural dyes from historical objects
Ramešová, Šárka ; Schwarzová, Karolina (advisor) ; Navrátil, Tomáš (referee)
The oxidation of quercetin (3,3',4',5,7-pentahydroxyflavone) and luteolin (3',4',5,7-tetrahydroxyflavone) has been studied. These intensively coloured polyphenolic compounds belong to a large group of naturally occuring flavonoid compounds. They were used with advantage as colourants in old tapestries. The study concerns the analysis of degradation processes of the original dyes. Degradation products formed during the ageing process can be used as fingerprints for the determination of the original colours. The degradation processes of flavonoid compounds were studied by electrochemical methods, absorption spectrometry and separation methods in aqueous media. The oxidation mechanism involves electron transfer coupled with chemical reaction and is influenced by the acidobasic properties of quercetin. The dissociation constants pK1 and pK2 of quercetin and pK1 and pK2 of luteolin were determined by combining of independent methods: acid-base titration and UV-Vis spectroscopy. The stability of both compounds significantly depends on the presence of the oxygen. The distribution of the oxidation products of quercetin in aqueous media within the exposure to oxygen was monitored by LC-MS/MS and LC- DAD analysis.
|
|
|
Physico-Chemical Properties of Drugs
Tomanová, Pavla ; Kubíček, Vladimír (advisor) ; Nováková, Veronika (referee)
Charles University Faculty of Pharmacy in Hradec Králové Department of biophysics and physical chemistry Author: Pavla Tomanová Supervisor: Ing. Vladimír Kubíček, CSc. Thesis title: Physico-Chemical properties of drugs This thesis deals with measuring dissociation constants (the pKa value) and the lipophilicity of nitrogenous heterocycle derivatives produced at the Faculty of Pharmacy in Hradec Králové. Two methods were used to determine the pK value: potentiometric titration and spectrophotometry. Potentiometric titration almost invariably produced relatively exact results, however the results of pK value obtained by spectrophotometry were sometimes difficult to replicate. Dissociation constants were compared on the basis of the method applied, and also with the theoretically determined dissociation constant calculated by means of the ChemDraw Ultra 12.0 software. The results obtained by the two experimental methods turned out to be very similar, corresponding to the theoretical pK value. Lipophilicity is another essential property of drugs tested in the preclinical stage. It specifies the aqueous or lipophilic phase affinity of a drug, substantially affecting the drug's ADMET in organism. Lipophilicity was determined on the basis of capacity factor value identified by RP-HPLC measurement using...
|
|
|
Physico-Chemical Properties of Drugs
Tomanová, Pavla ; Kubíček, Vladimír (advisor) ; Nováková, Veronika (referee)
Charles University Faculty of Pharmacy in Hradec Králové Department of biophysics and physical chemistry Author: Pavla Tomanová Supervisor: Ing. Vladimír Kubíček, CSc. Thesis title: Physico-Chemical properties of drugs This thesis deals with measuring dissociation constants (the pKa value) and the lipophilicity of nitrogenous heterocycle derivatives produced at the Faculty of Pharmacy in Hradec Králové. Two methods were used to determine the pK value: potentiometric titration and spectrophotometry. Potentiometric titration almost invariably produced relatively exact results, however the results of pK value obtained by spectrophotometry were sometimes difficult to replicate. Dissociation constants were compared on the basis of the method applied, and also with the theoretically determined dissociation constant calculated by means of the ChemDraw Ultra 12.0 software. The results obtained by the two experimental methods turned out to be very similar, corresponding to the theoretical pK value. Lipophilicity is another essential property of drugs tested in the preclinical stage. It specifies the aqueous or lipophilic phase affinity of a drug, substantially affecting the drug's ADMET in organism. Lipophilicity was determined on the basis of capacity factor value identified by RP-HPLC measurement using...
|
|
|
Physico-Chemical Properties of Drugs
Tomanová, Pavla ; Kubíček, Vladimír (advisor) ; Nováková, Veronika (referee)
Charles University Faculty of Pharmacy in Hradec Králové Department of biophysics and physical chemistry Author: Pavla Tomanová Supervisor: Ing. Vladimír Kubíček, CSc. Thesis title: Physico-Chemical properties of drugs This thesis deals with measuring dissociation constants (the pKa value) and the lipophilicity of nitrogenous heterocycle derivatives produced at the Faculty of Pharmacy in Hradec Králové. Two methods were used to determine the pK value: potentiometric titration and spectrophotometry. Potentiometric titration almost invariably produced relatively exact results, however the results of pK value obtained by spectrophotometry were sometimes difficult to replicate. Dissociation constants were compared on the basis of the method applied, and also with the theoretically determined dissociation constant calculated by means of the ChemDraw Ultra 12.0 software. The results obtained by the two experimental methods turned out to be very similar, corresponding to the theoretical pK value. Lipophilicity is another essential property of drugs tested in the preclinical stage. It specifies the aqueous or lipophilic phase affinity of a drug, substantially affecting the drug's ADMET in organism. Lipophilicity was determined on the basis of capacity factor value identified by RP-HPLC measurement using...
|
|
|
Physico-Chemical Properties of Drugs
Suchý, Miroslav ; Kubíček, Vladimír (advisor) ; Nováková, Veronika (referee)
1. Abstract Charles University in Prague Faculty of Pharmacy in Hradec Kralove Department of Biophysics and Physical Chemistry Candidate: Miroslav Suchy Supervisor: Ing. Vladimir Kubicek, CSc. Title of Diploma Thesis: Physico-Chemical properties of drugs To test physico-chemical properties of new molecules is necessary during drug development. It could be helpful to understand or predict the pharmacokinetic parametres of a new drug in vivo/in vitro experiments. One of this parameters is a dissociation constant (pK). Dissociation constant is defined as " Number on pH scale, wherein is just fifty percent of molecule in a ionization condition". In real case this number can help us to know where in the gastro-intestinal tract (GIT) the drug will be absorbed. In GIT only molecules exhibiting pK from 3 to 11 could be absorbed. Out of this range it is not possible. In this work I would like to introduce the ways of experimental measurement of pK values. I was working with two methods to measure the pK values of water-soluble compounds. The spectrophotometric method and the potentiometric one. I had to find out, that potentiometric titration is primary method which gets us good and accurate results. Based on my measurement I evaluated the spectrophotometric method as the secondary method. Spectrophotometric method...
|
|
|
Microcalorimetry as a method to analyze protein interactions with ligands
Durčák, Jindřich ; Konvalinka, Jan (advisor) ; Vaněk, Ondřej (referee)
The interactions of proteins with their binding partners occur in every living organisms, in almost every cell process. Therefore the exploration of protein interactions forms significant part of biochemical research. It appears that even more valuable information than the value of equilibrium constants of these interactions is determination of individual energy components - changes in enthalpy and entropy. Thermodynamic analysis by isothermal titration calorimetry (ITC) can determine the changes in entropy and enthalpy caused by formation of complex of binding partners. Microcalorimetry is also an important optimization technique in development of new drugs, for example antiretrovirotics. Despite HIV is a virus known for over 30 years, intensive research has neither brought vaccine nor drug that would permanently cure patients. Already 26 drugs were approved, most of them target viral enzymes reverse transcriptase and protease. Antiretroviral treatment prevents the propagation of HIV and maintains immune system, but long - term use leads to resistance against drugs, which is caused by mutations in the target proteins. One of relatively new targets of therapeutic intervention is capsid core formation of during assembly of new virions. During the assembly many protein - protein interactions take...
|
guest ::
