Phosphateses (EC 3.1.3.x) are a group of enzymes that hydrolyze phosphoesters. That way they affect the energetic metabolism of a cell and its regulation. Phosphatases that dephosphorylate proteins are an integral part of signaling pathways, stress responses and they modulate enzymatic activity. This thesis deals with the study of phosphatases obtained from tobacco leaves (Nicotiana tabacum, L.). Solution of enzymes was prepared by extraction in both acidic and alkaline buffers. Through the use of the chromogenic substrate pNP-phosphate it was determined that there is a higher phosphatase activity in the glycosylated fraction than in the fraction that did not bind to Con A Sepharose. The research of the ions effect on the phosphatase activity has determined that Mg2+ and Ca2+ show positive effect on the phosphatase activity while the effect of Co2+ and Mn2+ is inhibitory. The Zn2+ ions have shown no effect whatsoever. The glycosylated phosphatases also dephosphorylated low-weight-molecular substrates phosphoserine, ATP and glucose-6-phosphate. The research of protein phosphatase activity discovered the affinity to the substrate phosvitin, although neither to casein nor its tryptic cleaves. Detailed experiments have shown that the pH optima for all the substrates lie from pH 5 to 6. Glycosylated phosphatases...

The thesis deals with the analysis of corrosion resistance of machinery used in wastewater treatment plants. The theoretical part of the thesis deals with the composition of waste water in terms of corrosion aggressiveness and describes the corrosive en-vironment in the WWTP. Furthermore, the types of corrosion are characterized and the exposed machinery of the WWTP with the highest level of corrosion is determined. The experimental part of the work is devoted to the analysis of corrosion resistance of corrosion-resistant austenitic steels and structural non-alloyed steels with duplex zinc coating and acrylate paint. Furthermore, structural low-alloyed steels with chemical-heat treatment by nitriding and ferritic nitrocarburizing in gas and structural non-alloyed steel with duplex system of phosphate + epoxy coating and zinc + epoxy coating are analysed as a possible replacement for stainless steels. The steels with duplex system of zinc + acrylate coating used in practice show little corrosion resistance (the first signs of corrosion after 12 h and 24 h). some chemical-heat treated steels and steel with duplex sys-tem of zinc + epoxy coating achieved the same corrosion resistance as stainless steels (264 h test time) and can be used in technical practice.

In the field of regenerative medicine, regeneration of cartilage defects (caused either by injury or age-related degeneration) has become a widely discussed topic. Nanofibrous scaffolds provide a suitable environment for cell adhesion, proliferation, differentiation, and also for the local involvement of bioactive substances. Nanofibrous scaffolds mimic the extracellular matrix (ECM) of hyaline cartilage. These scaffolds are seeded with autologous chondrocytes. After having been isolated from the patient, the cells must be cultivated in vitro in order to obtain a sufficient amount of chondrocytes. Scaffolds with cultivated chondrocytes are later implanted back into the pacient. Chondrocytes, however, when grown on a 2D tissue culture plastic rapidly de-differentiate and thus lose the ability to synthesize ECM molecules. The aim of the work was modulation of chondrogenic differentiation medium through finding the ideal concentration of chondrogenic supplements, composed of L-ascorbate-2-phosphate (A2P) and dexamethasone (DEX), in the culture of primary chondrocytes seeded on a nanofibrous polycaprolactone (PCL) scaffold. The effect of different concentrations of the chondrogenic supplements on chondrocyte adhesion to the scaffold and their proliferation and differentiation was studied. The influence...

In the field of regenerative medicine, regeneration of cartilage defects (caused either by injury or age-related degeneration, such as osteoporosis) has become a widely discussed topic. Nanofibrous scaffolds provide a suitable environment for cell adhesion, proliferation, differentiation, and also local involvement of bioactive substances. Nanofibrous scaffolds mimic the extracellular matrix (ECM) of hyaline cartilage and thus have the potential to treat cartilage defects. The aim of the work was modulation of chondrogenic differentiation medium through finding the ideal concentration of chondrogenic supplements, composed of ascorbate-2- phosphate and dexamethasone, in the culture of primary chondrocytes of pig origin seeded on a nanofibrous polycaprolactone (PCL) scaffold. The effect of different concentrations of the chondrogenic supplements on chondrocyte adhesion to the scaffold and their proliferation and differentiation was studied. Firstly, the influence of each of the supplements alone in the medium was studied, followed by study of effects of their combinations. Then, the supplements were incorporated into the nanofibers and their effect upon their release from the nanofibers was investiaged. The supplements were studied in 21-day experiments. The chondrogenic re- differentiation was best...

The work deals with the preparation and study of polyphosphate composites. Aluminum phosphates provide some unusual properties like high-heat resistance in terms of inorganic binders. The addition of chromium in the form of Cr2O3 or directly the bond with the aluminum-chromium-phosphate can improve the properties of this binder. Highly viscous Al2Cr(H2PO4)9 and Al3Cr(H2PO4)12 binders were prepared by dissolving Al(OH)3 and CrO3 in 85% phosphoric acid, and mixed with Al2O3 and Cr2O3 fillers. The composites were cured in the furnace at 150 °C for 24 h under pressure of 10 MPa. During the annealing at temperatures up to 1 500 °C changes in chemical structure of the cured composites were observed, leading to the understanding of the creation of crystalline phases and their eventual changes. The characterization of binders was mainly based on FT-IR, EDAX, TG-DTA and optical microscopy analyses.

Plants are able to cope with changing environmental conditions or withstand its adverse effects due to their plastic development. One way to adapt to fluctuating amounts of nutrients and water in the environment or the presence of toxic substances is to regulate the movement of substances between the plant and the environment. Beside other, this regulation is also possible at the level of the root system, by the formation of apoplastic barriers endodermis and exodermis. Some species posses endodermis only, in others exodermis in hypodrermal layers of the root can be found. These barriers differentiate in three stages and prevent free movement of coumpounds though apoplast. The transport to the symplast is the key point of regulating the uptake of substances into the plant and the endodermis is the fundamental structure. The presence of exodermis, however, affects the apoplast permeability of the surface root layers and can therefore influence the involvement of the primary cortex cells in the uptake of substances from the environment. In this work the impact of phosphate deficiency on the formation of apoplastic barriers was studied focusing on exodermis and the effect of its differentiation on the occurrence of membrane transporters and involvement of primary cortex cells in the uptake of...

The aim of this thesis is to investigate molecular mechanism of reactive oxygen species production by flavin dehydrogenases mitochondrial glycerol-3-phosphate dehydrogenase (mGPDH) and succinate dehydrogenase (SDH). Together, they represent important source of reactive oxygen species in mammalian mitochondria, but the mechanism of electron leak is still poorly understood. Because mechanisms of reactive oxygen species production by other complexes of respiratory chain are better characterized, they can serve as case studies to get insight into mechanisms of reactive oxygen species by flavin dehydrogenases. Relevant knowledge is therefore summarized in the first part of the thesis. To study the production of reactive oxygen species by the isolated flavin dehydrogenases, we used brown adipose tissue mitochondria solubilized by digitonin as a model. Enzyme activity measurements, hydrogen peroxide production studies by Amplex UltraRed fluorescence and luminol luminescence revealed flavin as the most likely source of electron leak in SDH under in vivo conditions, while we propose coenzyme Q binding site as the site of reactive oxygen species production in the case of mGPDH. Distinct mechanism of this production by the two dehydrogenases is also apparent from induction of reactive oxygen species...

Phosphorus is frequently a limiting factor for phytoplankton in freshwater ecosystems, because algae and cyanobacteria are able to incorporate it only in a dissolved inorganic form. Phytoplankton evolved several mechanisms to overcome phosphorus limitation. One of them is the production of extracellular phosphatases. These enzymes are excreted on the surface of cells or released to the environment. They hydrolyze organic molecules containing phosphorus, which can be then incorporated by cells. This mechanism can influence the competitiveness of algae living in environments that are characterised by long-term phosphorus limitation (that is caused e.g. by the effect of low pH). In this study the influence of phosphorus concentration and form on extracellular phosphatase activity under laboratory conditions was investigated. The two experimental strains of the genus Coccomyxa (Chlorophyta) were isolated from acidified localities with different phosphorus availability  Plešné Lake and Hromnické Lake. Extracellular phosphatase activity on a single-cell level was measured using the FLEA technique and fluorescence microscopy. The FLEA technique allows direct visualization of phosphatases on the cell surface by incubating the samples with the artificial substrate ELF® 97 phosphate. Extracellular...

This work deals with issues of application of the graphene material in the field of electrochemical energy storage. It includes basic graphene properties, the overview of methods for the production of lithium-iron-phosphate/graphene composites and results of different research approaches. The general aim is to present growing opportunity of application of graphene based composites in the electrochemical energy storage field. In the experimental part of this work, a electrochemical exfoliation of graphite and a production of LFP/G composites with different amount of graphene material and with different types of graphene material are carried out. This work includes also x-ray diffraction spectroscopy measurements and the evaluation of impacts of graphene additives on final properties of the electrochemical energy storage.

This thesis deals with liquid aprotic electrolytes based on sulfolane with added flame retardant. The theoretical part of the thesis explains concepts - mainly aprotic electrolytes, flame retardants, and their practical use. It also discusses lithium - ion accumulators and materials used in them while focusing on the electrolyte function. The practical part of the thesis aims to measure the properties of aprotic electrolytes: their conductivity, potential window and flashpoint. It also contains a review of the measurement results.