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61.
Pavel Řezanka Klára Navrátilová Pavel Žvátora David Sýkora Pavel Matějka Ivan Mikšík Václav Kašička Vladimír Král 《Journal of nanoparticle research》2011,13(11):5947-5957
In this study, spherical gold nanoparticles (GNPs) of 14.7 nm diameter, prepared by citrate reduction of a gold(III) salt
and characterized by UV–Vis absorption spectrometry and transmission electron microscopy, were modified by a covalent attachment
of 6I-O-(3-mercaptopropyl)β-cyclodextrin (β-CD-SH) or per-6-deoxy-per-6-mercapto-β-cyclodextrin (β-CD-SH7). Subsequently, via three
alternative approaches, β-CD-modified GNPs were immobilized onto the inner wall of the fused-silica (FS) capillaries and applied
as special stationary phases for open-tubular capillary electrochromatography (OT-CEC). The first immobilization procedure
was based on pre-derivatization of a FS capillary with (3-mercaptopropyl)trimethoxysilane (MPTMS) followed by subsequent reactions
with GNPs and β-CD-SH or β-CD-SH7. The other two preparation protocols took advantage of sol–gel approach gaining a significant
increase in the interaction surface for solutes. In both instances, the sol–gel created 3D structure was further covalently
modified with GNPs. Serving that purpose, either β-CD-SH7 modified GNPs were used for the immobilization into the sol–gel
matrix (“one-step sol–gel technique”) or native GNPs were immobilized first into the sol–gel matrix and subsequently modified
with β-CD-SH7 (“two-step sol–gel technique”). The separation performance of CD-GNPs modified FS capillaries was tested by
OT-CEC in reversed-phase mode applied to separation of a model mixture of five polyaromatic hydrocarbons. The highest separation
efficiencies were obtained with the capillaries prepared by two-step sol–gel technique. However, with respect to the relatively
low reproducibility of this method, the first of the above preparation procedures, i.e., a simple pre-derivatization of the
FS capillary with MPTMS ensued with β-CD-SH7-GNPs immobilization seems to be more feasible approach providing decent separation
efficiency. 相似文献
62.
Dr. Pavlína Košinová Dr. Radek Gažák Prof. Jean‐Luc Duroux Prof. Roberto Lazzaroni Prof. Vladimír Křen Prof. Xavier Assfeld Dr. Patrick Trouillas 《Chemphyschem》2011,12(6):1135-1142
Natural polyphenols are known to be oxidized by free radicals, which partially explains the antioxidant properties of a number of these compounds. This oxidation may also be used to synthesise new compounds of biological interest, for example, dimers. The present theoretical study describes the existing experimental evidence showing that silybin and dehydrosilybin [natural polyphenols isolated from milk thistle (Silybum marianum)] form dimers regioselectively. Based on DFT calculations, thermodynamic and kinetic values were computed in order to better understand the physicochemical behaviour of these dimerisation processes. Calculations showed that after H‐atom transfer (from polyphenol to radical), dimerisation could proceed in two steps: 1) bond formation and, when possible, 2) tautomerisation reorganisation. The former step is the limiting step, while the latter is crucial for the process to be thermodynamically favourable (ΔG<0). If this rearrangement is impossible then dimerisation is not feasible, or at least becomes a minor process (e.g., dehydrosilybin dimerisation after H‐atom abstraction from the 3‐OH group). This explains the regioselectivity of polyphenol dimerisation. 相似文献
63.
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65.
Richard Delanghe Roman Lávička Vladimír Souček 《Advances in Applied Clifford Algebras》2011,21(3):521-530
The aim of the paper is to study relations between polynomial solutions of generalized Moisil-Théodoresco (GMT) systems and polynomial solutions of Hodge-de Rham systems and, using these relations, to describe polynomial solutions of GMT systems. We decompose the space of homogeneous solutions of GMT system of a given homogeneity into irreducible pieces under the action of the group O(m) and we characterize individual pieces by their highest weights and we compute their dimensions. 相似文献
66.
67.
High‐throughput workflow for identification of phosphorylated peptides by LC‐MALDI‐TOF/TOF‐MS coupled to in situ enrichment on MALDI plates functionalized by ion landing
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Lukáš Krásný Petr Pompach Marcela Strnadová Radovan Hynek Karel Vališ Vladimír Havlíček Petr Novák Michael Volný 《Journal of mass spectrometry : JMS》2015,50(6):802-811
We report an MS‐based workflow for identification of phosphorylated peptides from trypsinized protein mixtures and cell lysates that is suitable for high‐throughput sample analysis. The workflow is based on an in situ enrichment on matrix‐assisted laser desorption/ionization (MALDI) plates that were functionalized by TiO2 using automated ion landing apparatus that can operate unsupervised. The MALDI plate can be functionalized by TiO2 into any array of predefined geometry (here, 96 positions for samples and 24 for mass calibration standards) made compatible with a standard MALDI spotter and coupled with high‐performance liquid chromatography. The in situ MALDI plate enrichment was compared with a standard precolumn‐based separation and achieved comparable or better results than the standard method. The performance of this new workflow was demonstrated on a model mixture of proteins as well as on Jurkat cells lysates. The method showed improved signal‐to‐noise ratio in a single MS spectrum, which resulted in better identification by MS/MS and a subsequent database search. Using the workflow, we also found specific phosphorylations in Jurkat cells that were nonspecifically activated by phorbol 12‐myristate 13‐acetate. These phosphorylations concerned the mitogen‐activated protein kinase/extracellular signal‐regulated kinase signaling pathway and its targets and were in agreement with the current knowledge of this signaling cascade. Control sample of non‐activated cells was devoid of these phosphorylations. Overall, the presented analytical workflow is able to detect dynamic phosphorylation events in minimally processed mammalian cells while using only a short high‐performance liquid chromatography gradient. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
68.
Arrival time distributions of product ions reveal isomeric ratio of deprotonated molecules in ion mobility–mass spectrometry of hyaluronan‐derived oligosaccharides
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Martina Hermannová Andreea‐Maria Iordache Kristína Slováková Vladimír Havlíček Helena Pelantová Karel Lemr 《Journal of mass spectrometry : JMS》2015,50(6):854-863
Hyaluronic acid is a naturally occurring linear polysaccharide with substantial medical potential. In this work, discrimination of tyramine‐based hyaluronan derivatives was accessed by ion mobility–mass spectrometry of deprotonated molecules and nuclear magnetic resonance spectroscopy. As the product ion mass spectra did not allow for direct isomer discrimination in mixture, the reductive labeling of oligosaccharides as well as stable isotope labeling was performed. The ion mobility separation of parent ions together with the characteristic fragmentation for reduced isomers providing unique product ions allowed us to identify isomers present in a mixture and determine their mutual isomeric ratio. The determination used simple recalculation of arrival time distribution areas of unique ions to areas of deprotonated molecules. Mass spectrometry data were confirmed by nuclear magnetic resonance spectroscopy. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
69.
The Identification of a Novel Highly Condensed Pentacyclic Heteroaromatic Ring System 1,3,5,5b,6,8,10,10b‐Octaazacyclopenta[h,i]Aceanthrylene and its Application in the Synthesis of 5,7‐Substituted Pyrazolo[4,3‐d]Pyrimidines
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Libor Havlíček Daniela Moravcová Vladimír Kryštof Miroslav Strnad 《Journal of heterocyclic chemistry》2015,52(3):669-673
Pyrazolo[4,3‐d]pyrimidines are of interest as potential kinase inhibitors. This article describes the formation of a novel highly conjugated, condensed, centrosymmetric heteroaromatic compound, 4,9‐dichloro‐2,7‐diisopropyl‐1,3,5,5b,6,8,10,10b‐octaazacyclopenta[h,i]aceanthrylene ( 3 ), during the chlorination of 5,7‐dihydroxypyrazolo[4,3‐d]pyrimidine ( 1 ) with phenylphosphonic dichloride. The nucleophilic attack of benzylamine on 3 afforded N‐benzyl‐5‐chloro‐3‐isopropyl‐1H‐pyrazolo[4,3‐d]pyrimidin‐7‐amine ( 6 ), which was further substituted to yield a pyrazolo[4,3‐d]pyrimidine analogue of roscovitine, a well‐known cyclin‐dependent kinase inhibitor. 相似文献
70.
This study proposes changes to the design and evaluation of the CO2 headspace test, which is used as a simple method for assessment of the complete biodegradability of surfactants. It presents a modified equation for the calculation of biodegradation. It is proposed that the solution of 7 mol L?1 sodium hydroxide commonly used in the process involving alkalinisation of the vial contents be replaced with 15 mol L?1 sodium hydroxide. The use of the higher hydroxide concentration leads to a significant reduction in the value of the blank CO2 headspace test. 相似文献