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1.
Ewelina Minta 《Tetrahedron letters》2005,46(11):1795-1797
Alkali metal trimethylsilanolates, TMSO−, M+, has been used for efficient conversion of methyl esters into their corresponding anhydrous acid salts under mild non-aqueous conditions. This strategy has been applied to SPPS for the preparation of neurotoxin cyclic analogues and in (S)-5-hydroxynorvaline synthesis. 相似文献
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Ewelina Nawrot 《Journal of fluorine chemistry》2006,127(7):943-947
N-Aryl substituted amides react with chlorodifluoromethane in the presence of concentrated aqueous sodium hydroxide and benzyltriethylammonium chloride (TEBAC) as a catalyst in benzene (phase-transfer catalysis, PTC), affording mixtures of N- and O-difluoromethyl substituted derivatives. Amide anions are involved in this process. The reaction carried out with oximes gives O-difluoromethyl oxime ethers. 相似文献
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The elucidation of structures of glutathione (GSH) complexes play an important role in the fundamental understanding of biochemical pathways of metal ion deactivation in plants. This article attempts to feature key studies for stoichiometry of metal complexes with glutathione and its constituent amino acids to obtain a better understanding of the different metal affinities of the complexation sites of glutathione. The SEC-ICP-MS experiments have indicated that oxidation process of glutathione was accelerated by metal ion presence in following order Cu+, Pb2+ and Cd2+. The redox activity of metal ions was confirmed by ESI-MS experiments, which allowed to observe formation of glutathione disulphide (GSSG) in time. The stoichiometry of Cd2+, Cu+ and Pb2+ complexes with GSH was defined by observing the isotope pattern of investigated metals and hydrogen loss or transfer during binding. The complexes with metal bound to sulphur of 1:1 and 1:2 stoichiometry were found in case of cadmium and lead. The number of hydrogen atoms lost during metal binding and the SEC-ESI-MS results allowed to elucidate that copper is bound by GSSG in ratio 1:1 and 1:2. Additionally, size exclusion chromatography coupled to electrospray MS allowed to differentiate more stable complexes from weak ones that could be created in the gas phase. 相似文献
4.
Ewelina Pogorzelska-Nowicka Marcin Kurek Monika Hanula Agnieszka Wierzbicka Andrzej Ptorak 《Molecules (Basel, Switzerland)》2022,27(14)
Meat is a rich source of various nutrients. However, it needs processing before consumption, what in turn generates formation of carcinogenic compounds, i.a., polycyclic aromatic hydrocarbons (PAH), nitrosamines (NOCs), and the most mutagenic heterocyclic aromatic amines (HAAs). It was widely found that many factors affect the content of carcinogens in processed meat. However, it has recently been discovered that after digestion free HAAs are released, which are not detectable before enzymatic treatment. It was established that the highest percentage of carcinogens is released in the small intestine and that its amount can be increased up to 6.6-fold. The change in free HAAs content in analyzed samples was dependent on many factors such as meat type, doneness, particle size of meat, and the enzyme concentration used for digestion. In turn, introduction of bacteria naturally occurring in the human digestive tract into the model significantly decreases total amount of HAAs. Contrary, the addition of food ingredients rich in polyphenols, fiber, and water (pepper powder, onions, apples) increases free HAAs’ release up to 56.06%. Results suggests that in vitro digestion should be an integral step of sample preparation. Artificial digestion introduced before chromatographic analysis will allow to estimate accurately the content of carcinogens in processed meat. 相似文献
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Ewelina Ciecierska Anna Boczkowska Krzysztof Jan Kurzydlowski Iosif Daniel Rosca Suong Van Hoa 《Journal of Thermal Analysis and Calorimetry》2013,111(2):1019-1024
The paper concerns thermal properties of epoxy/nanotubes composites for aircraft application. In this work, influence of carbon nanotubes on thermal stability, thermal conductivity, and crosslinking density of epoxy matrix was determined. Three kinds of nanotubes were used: non-modified with 1- and 1.5-μm length, and 1-μm length modified with amino groups. Scanning electron microscopy observations were done for examining dispersion of nanotubes in the epoxy matrix. Glass transition temperature (T g) was readout from differential scanning calorimetry. From dynamic mechanical analysis, crosslinking density was calculated for epoxy and its composites. Also, thermogravimetric analysis was done to determine influence of nanotubes addition on thermal stability and decomposition process of composites. Activation energy was calculated from TGA curves by Flynn–Wall–Ozawa method. Thermal diffusivity was also measured. SEM images proved the uniform dispersion of carbon nanotubes without any agglomerates. It was found that nanotubes modified with amino groups lead to the increase of epoxy matrix crosslinking density. The significant increase in T g was also observed. On the other hand, addition of carbon nanotubes leads to the decrease of thermal stability of polymer due to the increase of thermal diffusivity. 相似文献
7.
Antoni W. Morawski Ewelina Kusiak-Nejman Jacek Przepiórski Roksana Kordala Juliusz Pernak 《Cellulose (London, England)》2013,20(3):1293-1300
TiO2/N-cellulose nanocomposite was successfully prepared in the (cyclohexyl)hexyl-dimethylammonium acetate–dimethyl sulfoxide solution. The obtained composite was characterized with various techniques like UV–Vis/DR, FTIR/DRS, X-ray diffraction, thermogravimetric analysis, DLS method and BET SSA measurements. TiO2/N-cellulose nanocomposite exhibited high UV–Vis light absorption with energy gap shifted to the visible region. Additive of TiO2/N photocatalyst to cellulose-IL-DMSO solution leads to obtaining the material with higher thermostability and limited photoactivity. 相似文献
8.
Prof. Dr. Antoni W. Morawski Dr. Ewelina Kusiak-Nejman Dr. Iwona Pełech Katarzyna Ćmielewska Dr. Daniel Sibera Piotr Staciwa Dr. Agnieszka Wanag Marcin Gano Dr. Ewa Ekiert Dr. Joanna Kapica-Kozar Kordian Witkowski Prof. Dr. Urszula Narkiewicz 《ChemistryOpen》2022,11(4):e202100262
A new approach to hydrogen production from water is described. This simple method is based on carbon dioxide-mediated water decomposition under UV radiation. The water contained dissolved sodium hydroxide, and the solution was saturated with gaseous carbon dioxide. During saturation, the pH decreased from about 11.5 to 7–8. The formed bicarbonate and carbonate ions acted as scavengers for hydroxyl radicals, preventing the recombination of hydroxyl and hydrogen radicals and prioritizing hydrogen gas formation. In the presented method, not yet reported in the literature, hydrogen production is combined with carbon dioxide. For the best system with alkaline water (0.2 m NaOH) saturated with CO2 under UV-C, the hydrogen production amounted to 0.6 μmol h−1 during 24 h of radiation. 相似文献
9.
Emilia Janiszewska-Turak Katarzyna Rybak Ewelina Grzybowska Ewelina Konopka Dorota Witrowa-Rajchert 《Molecules (Basel, Switzerland)》2021,26(12)
Vegetable processing pomace contains valuable substances such as natural colors that can be reused as functional ingredients. Due to a large amount of water, they are an unstable material. The aim of our research was to assess how the pretreatment method (thermal or nonthermal) affects the properties of powders obtained from beet juice and pomace after the freeze-drying process. The raw material was steamed or sonicated for 10 or 15 min, and then squeezed into juice and pomace. Both squeezed products were freeze-dried. The content of dry substance; L*, a*, and b* color parameters; and the content of betalain pigments were analyzed. Pretreatments increased the proportion of red and yellow in the juices. Steam and ultrasound caused a significant reduction in parameter b* in the dried pomace. A significant increase in betanin in lyophilizates was observed after pretreatment with ultrasound and steam for 15 min. As a result of all experiments, dried juices and pomaces can also be used as a colorant source. However, there is higher potential with pomaces due to their additional internal substances as well as better storage properties. After a few hours, juice was sticky and not ready to use. 相似文献
10.
Peptides derivatized with bicyclic quaternary ammonium ionization tags. Sequencing via tandem mass spectrometry
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Bartosz Setner Magdalena Rudowska Ewelina Klem Marek Cebrat Zbigniew Szewczuk 《Journal of mass spectrometry : JMS》2014,49(10):995-1001
Improving the sensitivity of detection and fragmentation of peptides to provide reliable sequencing of peptides is an important goal of mass spectrometric analysis. Peptides derivatized by bicyclic quaternary ammonium ionization tags: 1‐azabicyclo[2.2.2]octane (ABCO) or 1,4‐diazabicyclo[2.2.2]octane (DABCO), are characterized by an increased detection sensitivity in electrospray ionization mass spectrometry (ESI‐MS) and longer retention times on the reverse‐phase (RP) chromatography columns. The improvement of the detection limit was observed even for peptides dissolved in 10 mM NaCl. Collision‐induced dissociation tandem mass spectrometry of quaternary ammonium salts derivatives of peptides showed dominant a‐ and b‐type ions, allowing facile sequencing of peptides. The bicyclic ionization tags are stable in collision‐induced dissociation experiments, and the resulted fragmentation pattern is not significantly influenced by either acidic or basic amino acid residues in the peptide sequence. Obtained results indicate the general usefulness of the bicyclic quaternary ammonium ionization tags for ESI‐MS/MS sequencing of peptides. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献