Über die meßbaren Funktionen

Ohne Zusammenfassung     

Photodynamic Crosslinking of Proteins. III. Kinetics of the FMN- and Rose Bengal-sensitized Photooxidation and Intermolecular Crosslinking of Model Tyrosine-containing N-(2-Hydroxypropyl)methacrylamide Copolymers

As part of a study on the role of Tyr residues in the photosensitized intermolecular crosslinking of proteins, we have surveyed the kinetics of the rose bengal- and flavin mononucleotide (FMN)-sensitized photooxidation and crosslinking of a water-soluble N-(2-hydroxypropyl)methacrylamide copolymer with attached 6-carbon side chains terminating in tyrosinamide groups (thus the -OH group of the Tyr is free, but both the amino and carboxyl groups are blocked, simulating the situation of a nonterminal Tyr in a protein). The intermolecular photodynamic crosslinking of the Tyr copolymer can result only from the formation of Tyr-Tyr (dityrosine) bonds, because the copolymer itself is not photooxidizable. Rose bengal, primarily a Type II (singlet oxygen) sensitizer, sensitized the rapid photooxidation of the Tyr residue in the Tyr copolymer only at high pH, where the Tyr phenolic group is ionized; crosslinking did not occur with rose bengal under any of the reaction conditions used. In contrast, FMN, which can sensitize by both Type I (free radical) and Type II processes, sensitized the photooxidation of the Tyr copolymer over the pH range 4-9.5. Also, significant photocrosslinking occurred, but only from pH 4 to 8, with a maximum rate at pH 6. Crosslinking required the presence of oxygen. Studies with inhibitors, D2O as solvent, catalase and superoxide dismutase indicated that the photooxidation and photocrosslinking of the Tyr copolymer with FMN at pH 6 were not mediated by singlet oxygen, superoxide or hydrogen peroxide. It appears that crosslinking involves the abstraction of an H atom from the Tyr phenolic group to give Tyr and FMN radicals. The Tyr radical in one Tyr copolymer can then react with a Tyr radical in another Tyr copolymer to give an intermolecular dityrosine crosslink.     

Determination of cyclodextrins and their derivatives by capillary electrophoresis with indirect UV and conductivity detection

A fast and simple capillary electrophoretic method suitable for the determination of native α-, β-, γ-cyclodextrins, their randomly substituted tert-butyl derivatives (average degree of substitution 3.8 – 4.4), heptakis (2,6-di-O-methyl)- and heptakis (2,3,6-tri-O-methyl)-β-cyclodextrin was developed. Naphthyl-2-sulfonic acid (2-NSA), 3-iodobenzoic acid (3-IBA) and (1S)-1-phenylethylamine (PHEA) were tested as selective complex forming and UV absorbing background electrolyte additives. The composition of optimized background electrolyte for the separation of uncharged cyclodextrins and their derivatives was: 15 mM 3-iodobenzoic acid titrated with tris[hydroxymethyl]aminomethane to pH 8.0, 5% (v/v) of acetonitrile. A complete resolution of mono-2-O-, mono-3-O- and mono-6-O-carboxymethyl-β-cyclodextrin regioisomers was achieved in the optimized background electrolyte system: 40 mM PHEA titrated with 2-[N-morpholino]ethanesulfonic acid to pH 5.6. In addition to indirect UV detection a contactless conductometric detector was successfully utilized.     

Numerical Modelling of Wood Gasification in Thermal Plasma Reactor

Biomass gasification for synthesis gas production represents a promising source of energy based on plasma treatment of renewable fuel resources. Gasification/pyrolysis of crushed wood as a model substance of biomass has been experimentally carried out in the plasma-chemical reactor equipped with gas–water stabilized torch which offer advantage of low plasma mass-flow, high enthalpy and temperature making it possible to attain an optimal conversion ratio with respect to synthesis gas production in comparison with other types of plasma torches. To investigate this process of gasification in detail with possible impact on performance, a numerical model has been created using ANSYS FLUENT program package. The aim of the work presented is to create a parametric study of biomass gasification based on various diameters of wooden particles. Results for molar fractions of CO for three different particles diameters obtained by the modeling (0.55, 0.52 and 0.48) at the exit are relatively good approximation to the corresponding experimental value (0.60). The numerical results reveal that the efficiency of gasification and syngas production slightly decreases with increasing diameter of the particles. Computed temperature inhomogeneities in the volume of the reactor are strongest for the largest particle diameter and decrease with decreasing size of the particles.     

Measurement of gas solutions in small samples of intermetallic alloys

This article describes a measuring system that was proposed so as to enable measurement of the content of dissolved gas in samples, whose shape is determined by the specific requirements of the simultaneous measurements and cannot be modified to satisfy the requirements on solubility measurements. The apparatus — a dynamic UHV vacuum system — consists of a measuring chamber fitted with a heater based on electron bombardment, which permits a change in the sample temperature according to the selected schedule. The design of the heater permits reduction of additional heating in the actual measuring chamber, so that the increase in pressure caused by the action of the heater can be neglected. The measuring part of the system permits recording of changes in the overall pressure and partial pressures of selected gases in the measuring chamber. The lowest detectable amount of dissolved gas is less than 10⁻⁵ Pa m³. The results of measurement of the solubility of hydrogen in Ti and Fe aluminides in samples that are simultaneously used to measure the electrical conductivity are given as an example of the suitability of the apparatus for such measurements. This work is a part of research plan MSM 0021620834 financed by the Ministry of Education, Youth and Sports of the Czech Republic.     

Averaging over N-dimensional balls and Cauchy problem for equations of mathematical physics

In this paper, we deal with averaging over balls in E_N and derive an equality describing a relation between scale and space dependence of the average function. We also show connections with equations of mathematical physics.