National Repository of Grey Literature 20 records found  1 - 10next  jump to record: 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...
Influence of nanoparticles and polymers on the amyloid fibril formation
Holubová, Monika ; Štěpánek, Petr (advisor) ; Štěpánek, Miroslav (referee) ; Nardin, Corrine (referee)
The thesis deals with the testing of amyloidogenicity of various carbon nanoparticles and polymers. The first part of the thesis provides the theoretical background of amyloidoses, a group of diseases in which proteins are stored in the insoluble form of amyloid. In addition, the theoretical part also deals with a general overview of nanomaterials and the most important methods. Several types of nanomaterials were tested within the thesis, so the part Results and Discussion was divided into two subchapters: 1) Carbon nanospecies and amyloid fibril formation, and 2) Polysaccharides, glycogen modifications and amyloid fibril formation. The first subchapter concerns the testing of four types of carbon nanoparticles (single-walled carbon nanotubes (SWNT), fullerenes (C60), carbon quantum dots (CDs) and nanodiamonds (NDs)). These materials were tested on a model system hen egg white lysozyme (HEWL). Using fluorescence measurements and transmission electron microscopy (TEM), the nanoparticles were ranked from the most to the least amyloidogenic as follows: NDs> control> C60> CDs> SWNT. The second subchapter deals with the effect of selected polysaccharides (glycogen (GG), mannan (MAN), phytoglycogen (PG)) and modified GG on amyloid fibril formation. These materials were tested on the HEWL model system,...
Preparation of hybrid nanoparticles based on interaction of block polyelectrolytes with atypical ions
Mesíková, Soňa ; Matějíček, Pavel (advisor) ; Štěpánek, Miroslav (referee)
The Thesis deals with the co-assembly behaviour of cationic diblock copolymers poly(2- vinyl pyridine)-b-poly(ethylene oxide), P2VP-b-PEO, and poly(ethylene oxide)-b-poly(2- (N, N, N′, N′-tetramethyl guanidinium) ethyl acrylate), PEO-b-PGEA, with closo- dodecaborate anion, [B12H12]2- , in aqueous solutions. Formation of stable PEO-b- PGEA/[B12H12] nanoparticles was investigated by static and dynamic light scattering and 1 H NMR spectroscopy, and they were visualized as spherical nanoparticles by cryo- TEM imaging. According to the NMR results, both studied diblock copolymers form core- corona micelles with dodecaborate. The micellar molar mass and the aggregation number of PEO-b-PGEA/[B12H12] micelles were obtained in water and 0.156 M NaCl solution by standard Zimm method. For this, refractive index increment was evaluated by refractometer. The studied nanoparticles are promising for the boron delivery in medicine.
Interactions in solutions and gels of stimuli-responsive polymer systems investigated by NMR spectroscopy
Konefał, Rafał ; Spěváček, Jiří (advisor) ; Hrabal, Richard (referee) ; Štěpánek, Miroslav (referee)
Stimuli-responsive (stimuli-sensitive, intelligent, or smart) polymers are polymer materials which, after small external stimuli, evidently change their physical or chemical properties. Smart polymers can be classified according stimuli they respond to such as: temperature changes, mechanical stress, light irradiation, ultrasonic treatment, application of external magnetic as well as electric field, changes of pH, ionic strength, addition of the chemical agents and presence of biomolecules and bioactive molecules. Stimuli-responsive synthetic polymer systems has attracted considerable attention due to wide range of applications, i.e. controlled drug delivery and release systems, diagnostics, tissue engineering and 'smart' optical systems, as well as biosensors, microelectromechanical systems, coatings, and textiles. Among the types of stimuli for this dissertation temperature, pH and reactive oxygen species (ROS) responsive polymer systems were studied. In case of thermoresponsive polymers, when polymer chains are molecularly dissolved in a good solvent, changes (increasing or decreasing) of temperature result in insolubility (globular nanoparticles formation) of polymer chains, called temperature induced phase-separation. pH responsive polymers change properties such as: solubility, volume (gels),...
Scattering and spectroscopic studies of polyelectrolytes and associating block copolymers
Škvarla, Juraj ; Štěpánek, Miroslav (advisor) ; Špírková, Milena (referee) ; Humpolíčková, Jana (referee)
This dissertation focuses on application of scattering and spectroscopic techniques for studies of self-assembled systems of amphiphiles (both polymeric and low-molar mass) and polyelectrolytes in aqueous solutions. Special attention was paid to optical methods, namely static, dynamic and electrophoretic light scattering and steady-state and time-resolved fluorescence spectroscopy, which were supported by a number of other techniques such as small-angle X-ray scattering or transmission electron microscopy. The dissertation brings new results regarding micellization behavior of perfluorinated surfactants, self-assembly and stability of thermoresponsive amphiphilic block copolymers and counterion condensation on polyelectrolytes in aqueous solution.
Nanoparticles formed by complexes of copolymers with low-molar-mass compounds
Vojtová, Jana ; Štěpánek, Miroslav (advisor) ; Filippov, Sergej (referee) ; Hoffmann, Ingo (referee)
This thesis is focused on mixed systems of various copolymers (double hydrophilic block and gradient polyelectrolytes, hydrophobic graft copolymers) and low-molar-mass compounds (sodium dodecyl sulfate as a representative of a ionic surfactant or superparamagnetic iron oxides in the form of nanocrystals). The electrostatic and hydrophobic interactions in the studied systems in aqueous solutions leading to aggregation behavior and to the formation of co-assembled nanoparticles were investigated by combination of scattering and microscopy techniques, including light, X-ray and neutron scattering, electron microscopy and atomic force microscopy. Powered by TCPDF (

National Repository of Grey Literature : 20 records found   1 - 10next  jump to record:
See also: similar author names
24 ŠTĚPÁNEK, Martin
4 Štěpánek, Marek
24 Štěpánek, Martin
7 Štěpánek, Matěj
1 Štěpánek, Michael
9 Štěpánek, Michal
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