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91.
Barbara Grzeszczyk Kamila Poławska Yasser M. Shaker Sebastian Stecko Adam Mames Magdalena Woźnica Marek Chmielewski Bartłomiej Furman 《Tetrahedron》2012,68(52):10633-10639
Kinugasa reactions between terminal acetylenes and six-membered ring nitrones when one or both components are chiral, proceed in a low to moderate yield and with a high diastereoselectivity affording mostly one, dominant β-lactam product. The first step of the reaction is controlled by the configuration of the nitrone, whereas the protonation of the C-7 center of the carbacepham skeleton in the second step depends on: a) the configuration of the bridgehead carbon atom formed in the first step, b) epimerization process in the presence of a base, and c) on the configuration of the stereogenic center in the acetylenic partner. In the case of the nitrone derived from dihydroisoquinoline, the reaction proceeds in a more complex way affording not only β-lactams, but also products derived from the alternative regio-1,3-cycloaddition, or nucleophilic addition of the acetylene to the double bond of the nitrone. 相似文献
92.
Anna Palko-abuz Maria Baszczyk Kamila
roda-Pomianek Olga Wesoowska 《Molecules (Basel, Switzerland)》2021,26(15)
Isobavachalcone (IBC) is an active substance from the medicinal plant Psoralea corylifolia. This prenylated chalcone was reported to possess antioxidative, anti-inflammatory, antibacterial, and anticancer activities. Multidrug resistance (MDR) associated with the over-expression of the transporters of vast substrate specificity such as ABCB1 (P-glycoprotein) belongs to the main causes of cancer chemotherapy failure. The cytotoxic, MDR reversing, and ABCB1-inhibiting potency of isobavachalcone was studied in two cellular models: human colorectal adenocarcinoma HT29 cell line and its resistant counterpart HT29/Dx in which doxorubicin resistance was induced by prolonged drug treatment, and the variant of MDCK cells transfected with the human gene encoding ABCB1. Because MDR modulators are frequently membrane-active substances, the interaction of isobavachalcone with model phosphatidylcholine bilayers was studied by means of differential scanning calorimetry. Molecular modeling was employed to characterize the process of membrane permeation by isobavachalcone. IBC interacted with ABCB1 transporter, being a substrate and/or competitive inhibitor of ABCB1. Moreover, IBC intercalated into model membranes, significantly affecting the parameters of their main phospholipid phase transition. It was concluded that isobavachalcone interfered both with the lipid phase of cellular membrane and with ABCB1 transporter, and for this reason, its activity in MDR cancer cells was presumptively beneficial. 相似文献
93.
Kamila Klimaszewska Costel Sârbu Żaneta Polkowska Dariusz Lech Piotr Pasławski Stanisław Małek Jacek Namieśnik 《Central European Journal of Chemistry》2009,7(1):20-30
This paper presents the results of determination of selected characteristics (anions, cations, formaldehyde, hydrogen peroxide,
phenols, TC, TIC, TOC and metals) in dew samples collected in six different sites in Poland. The influence of local parameters
(e.g. wind speed, humidity) was investigated. Discriminant analysis was applied to the study of several dew samples collected from
different sampling sites covering six agglomerations in Poland. Discriminant function analysis was used not only for classifying
samples into different groups with a better than chance accuracy, but also for detecting the most important variables that
discern between the groups of samples considered. In this way it was possible to identify which ions or other physicochemical
features are responsible for the similarities or differences observed between different groups of dew samples. A good agreement
with their origin and location was observed. It is interesting to note that the classification of all samples was dominated
by pH, wind direction, pressure and temperature with a significant contribution of Na+ and Cl− ions.
相似文献
94.
ZnS nanoparticles were prepared and deposited on montmorillonite (MMT) in the presence of cetyltrimethylammonium (CTA). UV spectrometry and transmission electron microscopy (TEM) proved the formation of nanoparticles with diameters ranging from 3 nm to 5 nm. Selected-area electron diffraction (SAED) patterns revealed the presence of romboedric ZnS. The band gap energy of nanosize ZnS was estimated at 3.89 ± 0.03 eV. Photoluminescence spectra exhibited a strong emission band between 300 nm and 600 nm explained by the vacant ZnS nanostructure. The prepared ZnS-montmorillonite nanocomposite (ZnS-MMT) was used for the photocatalytic reduction of CO(2) providing a considerably high efficiency that exceeded 5-6-fold the results of commercial TiO(2) Degussa P25. The main reaction products were hydrogen and methane. Methanol and carbon oxide were also observed in about 7-fold lower amounts. The stability of ZnS against oxidation was confirmed by the determination of sulphate using capillary isotachophoresis. 相似文献
95.
Zdeněk Kameník Franz Hadacek Markéta Marečková Dana Ulanova Jan Kopecký Vladimír Chobot Kamila Plháčková Jana Olšovská 《Journal of chromatography. A》2010,1217(51):8016-8025
A fingerprinting method for chemical screening of microbial metabolites, potential antibiotics, in spent cultivation broths is described. The method is based on high-throughput ultra-high-performance liquid chromatography (UHPLC) separation with UV detection (photodiode array detector). Thirteen antibiotic standards and four cultivation broths were used for the method development. The comparison of ten liquid–liquid and solid phase extraction protocols for sample clean-up and pre-concentration revealed that Oasis HLB C18 sorbent gives the best recoveries. The Acquity BEH C18 chromatographic column was chosen for the samples separation with respect to its universality, selectivity, efficiency and robustness. The method is presented by two 3D fingerprints for every sample that was obtained under different, acidic and alkaline, UHPLC conditions. The acidic mobile phase consisted of 0.5% phosphoric acid with methanol and the alkaline mobile phase of 1 mM ammonium formate, pH 9 with acetonitrile. Each pair of 3D fingerprints includes the following physico-chemical information: polarity (retention time), presence and characterization of chromophores (UV spectra), compound concentration (detector response), and acid–base properties (influence of different pH of the aqueous parts of mobile phases on retention times). The sample extraction and method validation were assessed with relative standard deviation (RSD) of 0.5, 5.0 and 20.0% for retention times, peak areas and minor compound peak areas, respectively. 相似文献
96.
Anita R. Taulbee-Combs Matthew J. Bachus Kamila M. Wiaderek William H. Steinecker Zechariah D. Sandlin James A. Cox Gilbert E. Pacey 《Journal of Sol-Gel Science and Technology》2010,56(2):134-140
Terahertz (THz) time-domain reflectance spectroscopy is evaluated as a technique for nondestructive analysis of sol–gels over
the first week of aging without directly contacting or disturbing the sol–gels. In the sol–gels analyzed, tetramethyl orthosilicate
(TMOS) is the precursor and polyamidoamine (PAMAM) dendrimers are incorporated into each of two sol–gel sample groups; a third
control group contains no dendrimer. The study reports data acquired during sol–gel aging in contrasting humidity and ventilation
conditions and determines statistically whether the inclusion of a particular dendrimer and/or the humidity and air circulation
of the environment produce significant differences in the THz reflectance intensity observed throughout the first week of
sol–gel aging. The results of this study are correlated with previous studies of the same three species analyzed using AFM,
impact testing and nitrogen adsorption. The correlations are used to interpret the THz reflectance intensity differences between
the sol–gel groups studied using the previously reported results from established methods of analysis regarding the influence
of each dendrimer on polymer density, pore size and distribution, and homogeneity of the resulting amorphous silica monoliths. 相似文献
97.
Gabriela P. Aguiar Kamila A. L. Wakabayashi Guilherme F. Luz Vilma B. Oliveira Leda Mathias Ivo J. C. Vieira Raimundo Braz‐Filho Antonio E. M. Crotti 《Rapid communications in mass spectrometry : RCM》2010,24(3):295-308
The fragmentation of six plumeran indole alkaloids (PIAs) previously isolated from Aspidosperma spruceanum has been investigated by electrospray ionization tandem mass spectrometry (ESI‐MS/MS) in the positive ion mode. The fragmentation pathways have been established on the basis of MS/MS experiments using fragment ions generated in‐source and deuterium‐labeled alkaloids as precursor ions and on the basis of accurate mass measurements. Our results demonstrated that the fragmentation routes observed for the protonated PIAs are essentially derived from a pericyclic reaction and from the opening of rings D and E, followed by 1,4‐hydrogen rearrangements. Product ions resulting from radical eliminations were also observed, contrary to the ‘even‐electron rule’. Our data reveals that some product ions from protonated PIAs provide crucial information for the characterization of the acyl substituent at N‐1, the methoxyl and hydroxyl groups at the aromatic moiety, and give evidence of an ether bridge between C‐18 and C‐21. The data reported here were used for the dereplication of these compounds in a stem bark methanolic extract of Aspidosperma spruceanum. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
98.
Kamila Goderska Artur Szwengiel Zbigniew Czarnecki 《Applied biochemistry and biotechnology》2014,173(8):2189-2197
Lactobionic acid is a relatively new product derived from lactose oxidation, with high potential applications as a bioactive compound. Conducted experiments confirmed that both the time and temperature influenced the production of lactobionic acid during bioconversion of lactose using the Pseudomonas taetrolens bacteria. The study also investigated the effect of inoculum concentration on the production of lactobionic acid as a result of oxidation of whey-derived lactose. The highest concentration of lactobionic acid during oxidation of whey-derived lactose at a temperature of 30 °C by microorganisms. P. taetrolens was obtained during 50-h oxidation of the medium, which contained 25 % addition of the inoculum, in which the count of live cells was 2.85?×?109 CFU/ml. 相似文献
99.
4,4‐Dialkyl and 4,4‐diaryl‐4H‐benzo[d][1,3]oxathiin‐2‐ones were synthesized by the reaction of 2‐(mercapto‐phenyl)‐dialkyl‐ (or diaryl)‐methanol with CDI in excellent yield. The 2‐(mercaptophenyl)‐dialkyl‐ (or diaryl)‐methanols were prepared by the reaction of commercially available methylthiosalicylate with an appropriate alkyl or aryl Grignard reagent. 相似文献
100.
Kamila Malecka Iwona Grabowska Jerzy Radecki Anna Stachyra Anna Góra‐Sochacka Agnieszka Sirko Hanna Radecka 《Electroanalysis》2013,25(8):1871-1878
A DNA biosensor for the detection of specific oligonucleotide sequences of Avian Influenza Virus type H5N1 has been proposed. The NH2‐ssDNA probe was deposited onto a gold electrode surface to form an amide bond between the carboxyl group of thioacid and the amino group from ssDNA probe. The signals generated as a result of hybridization were registered in square wave voltammetry and electrochemical impedance spectroscopy in the presence of [Fe(CN)6]3?/4? as a redox marker. The genosensor is capable to determine 20‐mer and 180‐bp (PCR products) oligonucleotides complementary sequences with detection limit in the fM range. The genosensor displays good selectivity and sensitivity. The 20‐mer as well as 180‐bp oligonucleotides without a complementary sequence generate very low signal. 相似文献