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排序方式: 共有256条查询结果,搜索用时 16 毫秒
161.
Miloš Lukáč Martin Pisárčik Mária Garajová Martin Mrva Aneta Dušeková Andrej Vrták Renáta Horáková Branislav Horváth Ferdinand Devínsky 《Journal of surfactants and detergents》2020,23(6):1025-1032
A series of phosphonium amphiphilic compounds was synthesized. Cationic parts of molecules contain triphenylphosphonium moieties. Lipophilic parts of compounds are represented by straight alkyl chain or the alkyl chains which are ornamented by benzyl or metronidazole. The physicochemical properties of phosphonium amphiphilic compounds were investigated by the measurements of surface tension and conductivity. The critical micelle concentration (cmc), the surface tension value at the cmc (γcmc), the surface area at the surface saturation per head group (Acmc) were determined. The lowest cmc value was determined for phosphonium salts with straight dodecyl alkyl chain. Its value was 1.5 × 10−3 mol dm−3. Surface tension at the cmc decreases with the addition of bulky moieties (benzyl, radical from metronidazol) at the end of alkyl chains. Biological activities of compounds were studied on human erythrocytes and strains of Acanthamoeba lugdunensis and Acanthamoeba quina. Dodecyltriphenylphosphonium bromide showed the highest activity against Acanthamoeba. To the best of our knowledge, it is the first compound of the group of phosphonium amphiphiles, which exhibited high activity against Acanthamoeba. The determined structure–activity relationship indicated nonspecific trophocidal and hemolytic activity that depends on physicochemical properties of the studied compounds. 相似文献
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164.
Berit B. Rasmussen Kai Wang Johan G. Karstoft Søren N. Skov Morten Køcks Christina Andersen Aneta Wierzbicka Joakim Pagels Peter B. Pedersen Marianne Glasius Merete Bilde 《Indoor air》2021,31(4):1084-1094
Emissions from candles are of concern for indoor air quality. In this work, five different types of pillar candles were burned under steady burn conditions in a new laboratory scale system for repeatable and controlled comparison of candle emissions (temperature ~25°C, relative humidity ~13%, O2 >18%, air exchange rate 1.9 h−1). Burn rate, particle number concentrations, mass concentrations, and mode diameters varied between candle types. Based on the results, the burning period was divided in two phases: initial (0–1 h) and stable (1–6 h). Burn rates were in the range 4.4–7.3 and 4.7–7.1 g/h during initial and stable phase, respectively. Relative particle number emissions, mode diameters, and mass concentrations were higher during the initial phase compared to the stable phase for a majority of the candles. We hypothesize that this is due to elevated emissions of wick additives upon ignition of the candle together with a slightly higher burn rate in the initial phase. Experiments at higher relative humidity (~40%) gave similar results with a tendency toward larger particle sizes at the higher relative humidity. Chemical composition with respect to inorganic salts was similar in the emitted particles (dry conditions) compared to the candlewicks, but with variations between different candles. 相似文献
165.
Tobias Heck Dipl. Biol. Artur Reimer Dieter Seebach Prof. Dr. James Gardiner Dr. Gildas Deniau Dr. Aneta Lukaszuk Dr. Hans‐Peter E. Kohler Dr. Birgit Geueke Dr. 《Chembiochem : a European journal of chemical biology》2010,11(8):1129-1136
We have previously shown that the β‐aminopeptidases BapA from Sphingosinicella xenopeptidilytica and DmpA from Ochrobactrum anthropi can catalyze reactions with non‐natural β3‐peptides and β3‐amino acid amides. Here we report that these exceptional enzymes are also able to utilize synthetic dipeptides with N‐terminal β2‐amino acid residues as substrates under aqueous conditions. The suitability of a β2‐peptide as a substrate for BapA or DmpA was strongly dependent on the size of the Cα substituent of the N‐terminal β2‐amino acid. BapA was shown to convert a diastereomeric mixture of the β2‐peptide H‐β2hPhe‐β2hAla‐OH, but did not act on diastereomerically pure β2,β3‐dipeptides containing an N‐terminal β2‐homoalanine. In contrast, DmpA was only active with the latter dipeptides as substrates. BapA‐catalyzed transformation of the diastereomeric mixture of H‐β2hPhe‐β2hAla‐OH proceeded along two highly S‐enantioselective reaction routes, one leading to substrate hydrolysis and the other to the synthesis of coupling products. The synthetic route predominated even at neutral pH. A rise in pH of three log units shifted the synthesis‐to‐hydrolysis ratio (vS/vH) further towards peptide formation. Because the equilibrium of the reaction lies on the side of hydrolysis, prolonged incubation resulted in the cleavage of all peptides that carried an N‐terminal β‐amino acid of S configuration. After completion of the enzymatic reaction, only the S enantiomer of β2‐homophenylalanine was detected (ee>99 % for H‐(S)‐β2‐hPhe‐OH, E>500); this confirmed the high enantioselectivity of the reaction. Our findings suggest interesting new applications of the enzymes BapA and DmpA for the production of enantiopure β2‐amino acids and the enantioselective coupling of N‐terminal β2‐amino acids to peptides. 相似文献
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The stability of phenolic compounds of three strawberry cultivars was evaluated for changes during prefreezing treatments, storage and various freezing and thawing conditions. Polyphenol content was determined by HPLC-DAD-FL. The sum of assayed polyphenolic (proanthocyanidin and monomeric flavan-3-ols, anthocyanins, ellagic acid, p-coumaric acid) represented 2858.4 mg/kg in Kent, 2893.1 mg/kg in Elkat, and 2438.0 mg/kg in Senga Sengana. After freezing, 4.5-33.6% of polyphenols were lost; protective effects of prefreezing treatments were seen on anthocyanidins and proanthocyanidins: ascorbic acid was the most effective pretreatment, allowing retention of 3.9-27.5% of anthocyanins, and almost total recovery (3.9-23.9%) when associated with liquid nitrogen freezing. Pectin and sugar only allowed retention of 3.0-25.1% and 5.5-25.4% of the antocyanins, respectively. Thawing of the strawberries in a microwave oven (instead of 20 h at 20 °C) had a further positive effect on retention of anthocyanins, proanthocyanins, (+)-catechin and ellagic acid. 相似文献
168.
Aneta Jastrzębska 《European Food Research and Technology》2012,235(3):563-572
The selected biogenic amines, BAs (putrescine, cadaverine, histamine, tyramine, spermidine and spermine), in pork, beef, and poultry meat samples were determined by two simple procedures without derivatization using isotachophoretic technique. Two electrolyte systems were proposed for their separation and determination with satisfactory separation parameters. The linearity of the proposed procedures was between 2–10 mg L?1 and 5–50 or 10–60 mg L?1, whereas average recoveries for the standard solutions of amines and their mixture varied between 99–100 % and 95–105 %, respectively. Average recoveries for standard addition method (96–99 %) indicated satisfactory accuracy of proposed electrolyte systems. The obtained coefficient of variation values for standard solutions and meat samples ranged from 0.62 to 4.54 % and from 0.56 to 6.03 %, respectively, which confirmed good repeatability. Except for spermidine and spermine, BAs levels in fresh meat samples were generally low. The effect of storage time on the content of biogenic amines in meat was also studied indicating the increase of BAs levels (excluding Spermine and Spermidine). 相似文献
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Beata Tyliska Benita Wiatrak aneta Czynikowska Aneta Ciela-Niechwiadowicz Elbieta Gbarowska Anna Janicka-Kos 《International journal of molecular sciences》2021,22(8)
In the present paper, new pyrimidine derivatives were designed, synthesized and analyzed in terms of their anticancer properties. The tested compounds were evaluated in vitro for their antitumor activity. The cytotoxic effect on normal human dermal fibroblasts (NHDF) was also determined. According to the results, all the tested compounds exhibited inhibitory activity on the proliferation of all lines of cancer cells (colon adenocarcinoma (LoVo), resistant colon adenocarcinoma (LoVo/DX), breast cancer (MCF-7), lung cancer (A549), cervical cancer (HeLa), human leukemic lymphoblasts (CCRF-CEM) and human monocytic (THP-1)). In particular, their feature stronger influence on the activity of P-glycoprotein of cell cultures resistant to doxorubicin than doxorubicin. Tested compounds have more lipophilic character than doxorubicin, which determines their affinity for the molecular target and passive transport through biological membranes. Moreover, the inhibitory potential against topoisomerase II and DNA intercalating properties of synthesized compounds were analyzed via molecular docking. 相似文献