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81.
A new CZE method relying on in-capillary reaction and direct UV detection at the wavelength 270 nm is presented for the simultaneous separation of the neutral carbohydrates xylitol, D-(-)-mannitol, sucrose, D-(+)-fucose, D-(+)-cellobiose, D-(+)-galactose, D-(+)-glucose, L-rhamnose, D-(+)-mannose, D-(-)-arabinose, D-(+)-xylose, and D-(-)-ribose. The alkaline electrolyte solution was prepared of 130 mM sodium hydroxide and 36 mM disodium hydrogen phosphate dihydrate. Separation of the sample mixture was achieved within 35 min. Calibration plots were linear in the range of 0.05-3 mM. Reproducibility of migration times was between 0.3 and 1.1%, and the detection limits for the analytes were 0.02 and 0.05 mM. The optimized method was applied for the determination of neutral monosaccharides in lemon, pineapple, and orange juices and a cognac sample. The methodology is fast since no other sample preparation except dilution is required. 相似文献
82.
Viitala T Hautala JT Vuorinen J Wiedmer SK 《Langmuir : the ACS journal of surfaces and colloids》2007,23(2):609-618
The adsorption of anionic phospholipids on silica was investigated by the dissipative quartz crystal microbalance (QCM) technique. Liposomes composed of 1 mM 80:20 mol % of 1-palmitoyl-2-oleyl-sn-glycero-3-phosphatidylcholine (POPC)/phosphatidic acid, POPC/phosphatidylglycerol, or POPC/phosphatidylserine in N-(2-hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid) buffer at pH 7.4 (with or without 3 mM of CaCl2) were examined. We have previously demonstrated that similar phospholipid coatings can be used in capillary electrochromatography as a stationary phase for the separation of analytes. In this work, we focus on the formation of the coatings and on the type of lipid structure formed on silica. The QCM investigation comprised qualitative results based on changes in frequency and resistance, and quantitative modeling of the obtained results. The latter was performed using the dissipative QCM, which measures the quartz crystal impedance, combined with equivalent circuit analysis. A previously developed coating and cleaning procedure for phospholipid-coated fused silica capillaries was adopted in this study, and the same silica-coated crystal was used throughout the QCM study. We will demonstrate in this work that the type of lipid structure formed on silica, that is, a rather rigid supported lipid bilayer or a viscoelastic supported vesicle layer (SVL), is highly dependent on the lipid and solvent composition. We also show for the first time that the modeling of the dissipative QCM data can be used to extract a more quantitative picture of an adsorbed SVL, because, so far, published studies have merely used the QCM data in a qualitative sense. 相似文献
83.
Kiriazis A Rüffer T Jäntti S Lang H Yli-Kauhaluoma J 《Journal of combinatorial chemistry》2007,9(2):263-266
As part of our continuing studies of polymer-supported pericyclic reactions for preparing biologically interesting heterocyclic compounds, we have introduced a traceless solid-phase synthesis of hexahydrocinnolines. We developed a method in which mild reaction conditions can be used for the hetero-Diels-Alder reactions on a polymeric support. The dienoic 3-vinyl-2-cyclohexenol attached to a Wang resin through an ether linkage undergoes [4 + 2] cycloaddition reaction with several azadienophiles. The highly stereoselective Diels-Alder reaction showed preferential formation of a single cycloadduct resulting from an anti attack of the dienophile on the polymer-bound diene. Trifluoroacetic acid-mediated cleavage of the polymer-bound cycloadducts yields fused nonaromatic hexahydrocinnolines in moderate yields in three steps. 相似文献
84.
The accumulation of heavy metals in fish has been extensively studied and well documented. However, the research has been mainly focused on the muscle tissue, while the distribution patterns among other tissues, such as liver and gills, have been mostly neglected. Within the present study, the concentrations of Ag, Al, As, B, Ba, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Se, Sr, Zn and Li in the muscle, gills, liver and intestine of the sterlet (Acipenser ruthenus) from the Danube River have been assessed by using the inductively-coupled plasma optical spectrometry. The analysis has revealed a high degree of differential accumulation of the studied heavy metals and trace elements in the tissues of the Danube sterlet. Liver appeared to be the main heavy metal storage tissue, while the lowest levels of analyzed metals were found in muscles. Heavy metal concentrations in the muscle were at acceptable levels for human consumption, except partly for cadmium. We conclude that, in order to enable a more efficient control of contaminants in fish products, there is an apparent need to resolve the problem of lack of legal limits for many metals in European legislation. 相似文献
85.
Salminen JP Karonen M Sinkkonen J 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(10):2806-2816
Tannins are chemically complex plant polyphenols and only little is known of their true molecule-specific anti-herbivore activities. Here we will show that modern tannin chemistry is able to reveal fully new types of tannins in plants together with new types of biological activities for the tannins. Most of these new findings relate to ellagitannins, one of the least studied and underestimated classes of bioactive plant polyphenols. 相似文献
86.
S. Sahin P. M?ki-Arvela M. Kangas K. Er?nen J. W?rnn? T. Salmi D. Yu. Murzin 《Kinetics and Catalysis》2012,53(6):673-683
The kinetic resolution of racemic 1-phenylethanol with ethyl acetate was investigated in a down-flow fixed-bed reactor operated in a continuous mode mainly at the molar ratio of 1: 3 in 400 mL toluene at 70°C. The catalytic activity of the immobilized lipase was studied by: (i) changing the flow rates, (ii) utilizing different substrate concentrations, (iii) applying step changes using ethyl acetate, ethyl benzene, acetic acid, acetophenone etc., (iv) investigating the inhibitory effect of either the desired or the stoichiometric products (R)-1-phenylethyl acetate and ethanol, respectively), (v) elucidating the effect of water on the activity and stability of the immobilized lipase. The residence time distribution and the reactor hydrodynamics were also discussed along with kinetic modelling. The results were linked to the one-pot reactions. 相似文献
87.
We apply the coherent-mode expansion to correlation functions used to describe the coherence properties of supercontinuum generated in nonlinear ?bers. We show that the leading term of the expansion represents the quasi-coherent part of the ?eld while the quasi-stationary part is embedded into the higher-order modes. The evolution of the modal expansion and the number of modes needed to describe the supercontinuum ?eld are also discussed. 相似文献
88.
Katri Huitu Ritva Kinnunen Jari Laamanen Sami Lehti Sourov Roy Tapio Salminen 《The European Physical Journal C - Particles and Fields》2008,58(4):591-608
In grand-unified theories (GUT), non-universal boundary conditions for the gaugino masses may arise at the unification scale
and may affect the observability of the neutral MSSM Higgs bosons (h/H/A) at the LHC. The implications of such non-universal gaugino masses are investigated for Higgs boson production in the SUSY
cascade decay chain
,
,
,
produced in pp interactions. In the singlet representation with universal gaugino masses only the light Higgs boson can be produced in this
cascade with the parameter region of interest for us, while with non-universal gaugino masses heavy neutral MSSM Higgs boson
production may dominate. The allowed parameter space in the light of the WMAP constraints on the cold dark-matter relic density
is investigated in the above scenarios for gaugino mass parameters. We also demonstrate that combination of representations
can give the required amount of dark matter in any point of the parameter space. In the non-universal case we show that heavy
Higgs bosons can be detected in the cascade studied in parameter regions with the WMAP preferred neutralino relic density. 相似文献
89.
We find a concrete integral formula for the class of generalized Toeplitz operators \(T_a\) in Bergman spaces \(A^p\), \(1<p<\infty \), studied in an earlier work by the authors. The result is extended to little Hankel operators. We give an example of an \(L^2\)-symbol a such that \(T_{|a|} \) fails to be bounded in \(A^2\), although \(T_a : A^2 \rightarrow A^2\) is seen to be bounded by using the generalized definition. We also confirm that the generalized definition coincides with the classical one whenever the latter makes sense. 相似文献
90.
Phospholipid-coated fused-silica capillaries with immobilized avidin were applied in the chiral separation of D,L-tryptophan, D,L-PTH-serine, and D,L-PTH-threonine at pH 7.4 by open-tubular CEC. Liposomes prepared from 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-N-(Cap biotinyl), or 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-N-(Biotinyl) with different amounts of phosphatidylserine were assessed as phospholipid coating materials. The stability of the coating and the success of the coating procedure were evaluated in terms of the repeatability of the enantiomer migration times and the resolution of enantiomers. The coating procedure itself significantly affected the migration times and resolution of the enantiomers. Reliable chiral separations with high separation efficiencies were achieved through careful choice of the coating method. 相似文献