National Repository of Grey Literature 6 records found  Search took 0.00 seconds. 
Multidimensional characterization of polyelectrolytes and interpolyelectrolyte complexes in aqueous solutions
Murmiliuk, Anastasiia ; Štěpánek, Miroslav (advisor) ; Šachl, Radek (referee) ; Hoffmann, Ingo (referee)
Multidimensional characterization of polyelectrolytes and interpolyelectrolyte complexes in aqueous solutions Abstract: This PhD thesis is dedicated to the study of polyelectrolytes and their self-assembly in aqueous solutions. The morphology and ionization state of individual polymer chains were investigated as well as their co-assembly with oppositely charged species. First, the charge regulation of short and long weak polyelectrolytes in aqueous solution was investigated to deeper understand their pH-responsive properties. The changes of ionization degree and charge of oligopeptides composed of 5 amino acids with acid side-chains and 5 with basic side chains were followed upon varying the pH in order to reveal the effect of interactions between the like-charged and oppositely charged groups. It was shown that intra-molecular electrostatic interactions and conformational flexibility caused the suppression of the total charge and enhancement of ionization of the peptides. To get an insight into the distribution of local H+ concentration in the proximity of a polyelectrolyte chain, a modified polyelectrolyte structure was used with a fluorescent pH- indicator, covalently attached at the end of the chain. Ionization of the pH-responsive fluorophore revealed its effective pK which was compared with the local...
Computational modeling of diffusion in polymer solutions
Kubečka, Jakub ; Košovan, Peter (advisor) ; Šachl, Radek (referee)
We performed coarse-grained molecular dynamics simulations of fully dissociated polyelectrolytes in the presence of monovalent and multivalent counterions and charged oligomers. The dynamics of these systems has been studied to follow internal dynamics of polyelectrolyte and counterions. The dynamics is presented via the mean square displacement which we obtain from the simulation trajectory and, moreover, via curves of Fluorescence Correlation Spectroscopy (FCS) obtained also from the simulation trajectory. FCS is an experimental technique which can be used to study condensation of counterions on polyelectrolytes. Therefore, we analyze the FCS curves and investigate applicability of various analytical models to fit these FCS curves. The aim of this work is a discussion about the fitting of the FCS curves and presentation of our observations for dynamics of counterions during condensation on the polyelectrolyte.
Localisation of Fluorescent Probes and the Estimation of Lipid Nanodomain Sizes by Modern Fluorescence Techniques
Šachl, Radek ; Hof, Martin (advisor) ; Obšil, Tomáš (referee) ; Almgren, Mats (referee)
iii Organizations Umeå University Department of Chemistry, Umeå, SE & Charles University in Prague, Faculty of Science, Prague, CZ Document name Doctoral thesis Date of issue February 2012 Author Radek Šachl Title Localisation of Fluorescent Probes and the Estimation of Lipid Nanodomain Sizes by Modern Fluorescence Techniques Abstract The thesis is divided into two major parts. The first part focuses on the localisation of probes in lipid/polymeric bilayers and in GM1 micelles. Included in this thesis is a new approach based on electronic energy transfer/migration (FRET/DDEM), which efficiently determines transversal positions of fluorescent molecules in lipid bilayers. This approach has been used to locate newly synthesized lipid probes in DOPC bilayers. The label was introduced at the end of sn-2 acyl chains of variable length. Analytical models accounting for FRET exist for a limited number of basic geometries. Here, a combination of FRET and Monte Carlo simulations enables the localisation of probes in bicelles and in bilayers containing pores, i.e. in lipid systems with variable curvature, or in non-homogenous lipid systems. This approach has been used to test whether conical-like fluorescence probes have an increased affinity to highly curved regions, which would enable preferential labelling of...
Light Scattering and Fluorescence Studies of Poly(ethylene oxide)-block-poly(ε-caprolactone) Self-assembled Nanoparticles
Šachl, Radek
The Diploma/Rigorous work is based on the following two publications: Šachl, R.; Uchman M.; Matĕjíček, P.; Procházka, K.; Štĕpánek, M.: Preparation and Characterization of

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