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排序方式: 共有755条查询结果,搜索用时 31 毫秒
31.
Michał Pieckowski Piotr Kowalski Ilona Olędzka Natalia Miękus-Purwin Alina Plenis Anna Roszkowska Tomasz Bączek 《Electrophoresis》2022,43(9-10):990-997
Mitotane is a cytotoxic drug used in the treatment of inoperable adrenocortical carcinoma, it inhibits steroidogenesis as well, and therefore monitoring the level of steroid hormones in patients treated with mitotane is a crucial point of therapy. Hence, we have developed a simple, fast, and efficient electrophoretic method combined with reverse polarity sweeping as online preconcentration technique and dispersive liquid–liquid microextraction for the simultaneous determination of mitotane, its main metabolite DDA, and five steroid hormones (progesterone, testosterone, epitestosterone, cortisol, and corticosterone) in urine samples. In addition, a new sample matrix consisting of β-CD2SDS1 complexes for a high hydrophobic compounds solubilization was developed. Approach based on the application of β-cyclodextrin and SDS complex of a ratio 2:1 allowed for hydrodynamic injection into the capillary of a solution containing both mitotane and other analytes. The detection limits of the analytes for the reverse polarity sweeping-dispersive liquid–liquid microextraction method were found to be in the range of 1.5–3 ng/mL, which were approximately 1000 times lower than in the conventional hydrodynamic injection (5 s, 0.5 psi) without any preconcentration procedure. All analytes were completely resolved in less than 13 min by uncoated silica capillary with an inner diameter of 75 μm (ID) × 60 cm. Electrophoretic separation was performed in reverse polarity with a voltage of –25 kV with a background electrolyte (BGE) consisting of 100 mM SDS, 25% ACN, 25 mM phosphate buffer (pH 2.5), and 7 mM β-cyclodextrin. 相似文献
32.
Facile Conversion of Red Phosphorus into Soluble Polyphosphide Anions by Reaction with Potassium Ethoxide 下载免费PDF全文
Dr. Alina Dragulescu‐Andrasi Dr. L. Zane Miller Dr. Banghao Chen Prof. D. Tyler McQuade Prof. Michael Shatruk 《Angewandte Chemie (International ed. in English)》2016,55(12):3904-3908
Soluble polyphosphide anions were successfully generated in a number of organic solvents by the reaction between shelf‐stable red phosphorus and potassium ethoxide. The species were identified by 31P NMR spectroscopy in solution and by X‐ray crystal‐structure determination of (Bu4N)2P16 in the solid state. The reaction was scaled up to gram quantities by using a flow‐chemistry process. 相似文献
33.
Polymerisation of vinyl acetate in microemulsions with methanol 总被引:1,自引:0,他引:1
D. Donescu L. Fusulan C. Petcu A.-G. Boborodea D.-S. Vasilescu 《Colloid and polymer science》2000,278(10):927-935
The homogeneity domains for the system vinyl acetate – methanol – monomaleate of nonylphenol ethoxylated with 25 mol ethylene
oxide as an aqueous solution (MEMNPEO25) (33%) have been studied; it has been shown that, due to the shorter chain of methanol,
these domains are more reduced than in the case of ethanol. The changes in refractive indexes and electrical conductivities
have shown the formation of microemulsions with different structures (water-in-oil, bicontinuous or oil-in-water). Ammonium
persulphate is soluble only in oil-in-water or in bicontinuous microemulsions. The initial polymerisation rates as well as
the decomposition rates for the initiator are apparently affected when the microemulsion structure is modified. The polymerisation
rate of vinyl acetate is higher in the presence of methanol than in the presence of ethanol for similar compositions; this
fact may be attributed to a higher degree of ionisation of the initiator in the presence of methanol. Also, in polymerisations
initiated by benzoyl peroxide, the conversions are influenced by the microstructure; thus, the maximum corresponds to water-in-oil
microemulsions. By measuring the amount of unreacted MEMNPEO25 (gel permeation chromatography) we were able to show that the
copolymer formed consisted of vinyl acetate and reactive surfactant.
Received: 9 March 1999/Accepted: 13 March 2000 相似文献
34.
Jan Eric Neuburger Alina Gazizova Sven Tiedemann Prof. Dr. Jan von Langermann 《European journal of organic chemistry》2023,26(34):e202201471
This study highlights the straight-forward synthesis of substituted 1,2-amino alcohols from simple and readily available aromatic methyl ketones. Starting from acetophenone derivatives, the straight-forward synthesis strategy involved an initial bromination of the alpha-positioned methyl group in the first step, followed by a simple hydrolysis to the hydroxyketone (2-hydroxyacetophenone). The hydroxylated intermediate was subsequently converted from Silicibacter pomeroyi to the final 1,2-amino alcohol by using the transaminase. The transaminase-catalyzed reaction proceeded with yields up to 62 % and always excellent enantiomeric excess of >99 %. Interestingly, the keto-enol-tautomerism of the hydroxyl ketone yields an unexpected amino alcohol isomer. 相似文献
35.
Gisle Atsang Kiki Raluca Maria Pop Octavia Sabin Ioana Corina Bocsan Veronica Sanda Chedea Sonia Ancua Socaci Alina Elena Prvu Egre Finsia Takvou Francis Zramah Mathieu Anca Dana Buzoianu 《Molecules (Basel, Switzerland)》2022,27(17)
Dichrostachys cinerea (L.) Wigth & Arn. (DC) is widely used in traditional medicine against several inflammatory diseases, especially rheumatoid arthritis, because of its antioxidant and anti-inflammatory effects. This study aimed to characterize the polyphenol-rich DC fruit extracts and investigate the analgesic, anti-inflammatory, and antioxidant effects in a rat inflammation model induced by complete Freund’s adjuvant (CFA). Water and ethanolic extracts were characterized using liquid chromatography coupled with mass spectrometry (LC-MS), Fourier-transform infrared (FTIR) spectroscopy, and gas chromatography coupled with mass spectrometry (GC-MS). The polyphenol-rich extracts were administered in three different concentrations for 30 days. Pain threshold, thermal hyperalgesia, edema, and serum biomarkers specific to inflammatory processes or oxidative stress were evaluated. Both extracts were rich in polyphenolic compounds, mainly flavan-3-ols, proanthocyanidins, and flavone glycosides, which had important in vitro antioxidant capacity. DC fruit extracts administration had the maximum antinociceptive and anti-inflammatory effects after one day since the CFA injection and showed promising results for long-term use as well. The measurement of pro-inflammatory cytokines, cortisol, and oxidative stress parameters showed that DC extracts significantly reduced these parameters, being dose and extract-type dependent. These results showed potential anti-inflammatory, analgesic, and antioxidative properties and revealed the necessity of using a standardized polyphenolic DC extract to avoid result variability. 相似文献
36.
The determination of the content of stable isotopes, 18O and 2H, respectively, in juice water facilitates the distinction between authentic juices and juices made from concentrates by
redilution with tap water. At the same time, the detection of C4 cane or corn-derived sugar syrups in fruit juices which are produced from C3 fruit types is thus facilitated by the characteristic differences in 13C/12C, expressed as δ
13C (‰) values due to photosynthetic CO2 assimilation via the C3−, C4−, and crassulacean acid metabolism pathways. In this study, the quantitative determination of water added to an authentic
juice, on the basis of δ
18O, and δ
2H values, respectively, was successfully performed. Also, the δ
18O, and δ
2H of juice water and δ
13C of the whole juice in 18 samples were also determined. The results obtained provided us with the possibility of distinguishing
between authentic fruit juices and those obtained by redilution of concentrated fruit juices and the detection of C4 type added sugar. 相似文献
37.
Dr. Gleb I. Tselikov Prof. Dr. Victor Yu Timoshenko Prof. Dr. Leonid A. Golovan Dr. Jürgen Plenge Alina M. Shatalova Georgiy A. Shandryuk Irina Yu Kutergina Alexey S. Merekalov Prof. Dr. Eckart Rühl Prof. Dr. Raisa V. Talroze 《Chemphyschem》2015,16(5):1071-1078
The photoluminescence (PL) of CdSe quantum dots (QDs) that form stable nanocomposites with polymer liquid crystals (LCs) as smectic C hydrogen‐bonded homopolymers from a family of poly[4‐(n‐acryloyloxyalkyloxy)benzoic acids] is reported. The matrix that results from the combination of these units with methoxyphenyl benzoate and cholesterol‐containing units has a cholesteric structure. The exciton PL band of QDs in the smectic matrix is redshifted with respect to QDs in solution, whereas a blueshift is observed with the cholesteric matrix. The PL lifetimes and quantum yield in cholesteric nanocomposites are higher than those in smectic ones. This is interpreted in terms of a higher order of the smectic matrix in comparison to the cholesteric one. CdSe QDs in the ordered smectic matrix demonstrate a splitting of the exciton PL band and an enhancement of the photoinduced differential transmission. These results reveal the effects of the structure of polymer LC matrices on the optical properties of embedded QDs, which offer new possibilities for photonic applications of QD–LC polymer nanocomposites. 相似文献
38.
Ioana Sisu Valentina Udrescu Corina Flangea Sorin Tudor Nicolae Dinca Lucian Rusnac Alina D. Zamfir Eugen Sisu 《Central European Journal of Chemistry》2009,7(1):66-73
A variety of carbohydrates, in particular polysaccharides can be subjected to chemical modification to obtain derivatives
with amphiphilic properties, which enable biochemical or biological reactions at the polymer surface. In the present work,
a polydisperse maltodextrin mixture of average molecular weight 3000 was coupled with 1,6-hexamethylenediamine (HMD) via reductive amination reaction. Resulting products were characterized by thermal analysis and positive nanoelectrospray quadrupole
time-of-flight (Q-TOF) mass spectrometry (MS) and tandem mass spectrometry (MS/MS). Both thermal analysis and MS screening
confirmed the formation of the HMD-polysaccharide coupling products. Moreover, HMD-linked polysaccharide chains containing
2 to 26 glucose building blocks were identified by nanoESI Q-TOF MS. MS/MS fragmentation using collision-induced dissociation
(CID) at low ion acceleration energies provided strong evidence for HMD-maltodextrin linkage formation and the set of sequence
ions diagnostic for the composition and structure of a HMD-linked chain containing 18 glucose residues.
相似文献
39.
Losego MD Guske JT Efremenko A Maria JP Franzen S 《Langmuir : the ACS journal of surfaces and colloids》2011,27(19):11883-11888
Self-assembled monolayers (SAMs) of alkanephosphonic acids with chain lengths between 8 and 18 carbon units were formed on thin films of indium tin oxide (ITO) sputter-deposited on silicon substrates with 400 nm thermally grown SiO(2). The silicon substrates, while not intended for use in near-IR or visible optics applications, do provide smooth surfaces that permit systematic engineering of grain size and surface roughness as a function of the sputter pressure. Argon sputter pressures from 4 to 20 mTorr show systematic changes in surface morphology ranging from smooth, micrometer-sized grain structures to <50 nm grains with 3× higher surface roughness. Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy experiments are conducted for alkanephosphonic acids deposited on these wide range of ITO surfaces to evaluate the effects of these morphological features on monolayer ordering. Results indicate that long-chain SAMs are more highly ordered, and have a smaller tilt angle, than short-chain SAMs. Surprisingly, the 1-octadecyl phosphonic acids maintain their order as the lateral grain dimensions of the ITO surface shrink to ~50 nm. It is only when the ITO surface roughness becomes greater than the SAM chain length (~15 ?) that SAMs are observed to become relatively disordered. 相似文献
40.
Sebastian Reimann Alina Bunescu Andranik Petrosyan Muhammad Sharif Silke Erfle Constantin Mamat Tariel V. Ghochikyan Ashot S. Saghyan Anke Spannenberg Alexander Villinger Peter Langer 《Helvetica chimica acta》2013,96(10):1955-1967
A variety of 6‐(trichloromethyl)salicylates (=2‐hydroxy‐6‐(trichloromethyl)benzoates) were prepared by TiCl4‐mediated cyclization of 1,3‐bis(trimethylsilyloxy)buta‐1,3‐dienes with 1,1,1‐trichloro‐4,4‐dimethoxybut‐3‐en‐2‐one. The employment of trimethylsilyl trifluoromethanesulfonate (Me3SiOTf) as Lewis acid resulted in the formation of trichloromethyl‐substituted cyclohexenones. The cyclizations proceeded with good‐to‐very‐good regioselectivities. 相似文献