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11.
Acetylenephosphonates carrying the XCF(2) group have been studied in a base-mediated heterocyclization reaction with selected 2-amino-3-formylchromones to give 2-difluoromethyl azaxanth-3-ylphosphonates. The presence of the fluorinated substituent determined the regioselectivity as well as the reactivity of this process. 相似文献
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Repetitive processes are a distinct class of two-dimensional systems (i.e. information propagation in two independent directions occurs) of both systems theoretic and applications interest. In this paper we introduce a new model for these processes in order to represent dynamics which arise in some applications areas and which are not included in those currently available. Then we proceed to de.ne quadratic stability for this case, obtain conditions for its existence, and also use feedback control to solve a stabilization problem. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Nonlinear Dynamics - Rotating machines are exposed to different faults such as shaft cracks, bearing failures, rotor misalignment, stator to rotor rub, etc. Therefore, turbo-generators, aircraft... 相似文献
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15.
Slominski A Semak I Zjawiony J Wortsman J Gandy MN Li J Zbytek B Li W Tuckey RC 《Chemistry & biology》2005,12(8):931-939
We demonstrate the metabolism of ergosterol by cytochrome P450scc in either a reconstituted system or isolated adrenal mitochondria. The major reaction product was identified as 17alpha,24-dihydroxyergosterol. Purified P450scc also generated hydroxyergosterol as a minor product, which is probably an intermediate in the synthesis of 17alpha,24-dihydroxyergosterol. In contrast to cholesterol and 7-dehydrocholesterol, cleavage of the ergosterol side chain was not observed. NMR analysis clearly located one hydroxyl group to C24, with evidence that the second hydroxyl group is at C17. 17alpha,24-Dihydroxyergosterol inhibited cell proliferation of HaCaT keratinocytes and melanoma cells. Thus, in comparison with cholesterol and 7-dehydrocholesterol, the 24-methyl group and the C22-C23 double bond of ergosterol prevent side chain cleavage by P450scc and change the enzyme's hydroxylase activity from C22 and C20, to C24 and C17, generating bioactive product. 相似文献
16.
Matejícek P Cígler P Olejniczak AB Andrysiak A Wojtczak B Prochazka K Lesnikowski ZJ 《Langmuir : the ACS journal of surfaces and colloids》2008,24(6):2625-2630
We report the first evidence that boron-containing nucleoside conjugates have a tendency to associate in water solutions. The size, charge, and exoskeletal pattern of the boron cluster can strongly influence the aggregation. The aggregation of nucleosides with attached boron clusters was observed using light scattering and atomic force microscopy techniques. Although the species containing either the bulky amphiphilic [3-cobalt(III) bis(1,2-dicarbollide)]- anion or the electroneutral dicarba-closo-dodecaboranyl moiety tend to form stable nanoparticles in aqueous solutions, the compounds bearing the smaller, negatively charged dicarba-nido-undecaboranyl moiety as well as the unmodified nucleosides do not aggregate. The light scattering measurements also showed that the aggregated species can interact with nonionic surfactant Triton X-100 in solution. The partition coefficients P in the water-octanol system correlate fairly well with the aggregation tendency observed by light scattering measurements. This finding allows us to predict the association behavior of boron-cluster-containing nucleosides on a qualitative level. The observed phenomenon can contribute to a better understanding of biological properties of boronated nucleosides and the design of boronated nucleoside-based drugs such as boron carriers for boron neutron capture therapy of tumors (BNCT) and antiviral agents. 相似文献
17.
Elzbieta Galezowska Joanna Kosman Agnieszka Stepien Blazej Rubis Maria Rybczynska Bernard Juskowiak 《Chemical Papers》2012,66(2):79-84
G-quadruplexes are a family of DNA secondary structures resulting from the folding of a guanine-rich sequence. Targeting quadruplexes
by small molecules is an approach that is currently being studied with the aim of exploring their biological roles and developing
new anti-cancer agents. There is evidence that the formation of G4 structures by telomeric DNA can be used to inhibit the
enzyme activity of telomerase, and thereby to activate the pathway to senescence in tumour cells. It was previously shown
that the papaverine oxidation products 6a,12a-diazadibenzo-[a,g]fluorenylium derivative (ligand I) and 2,3,9,10-tetramethoxy-12-oxo-12H-indolo[2,1-a]isoquinolinium chloride (ligand II) bind to G-quadruplex representing the human telomeric sequence. These ligands possess the ability to inhibit telomerase
and polymerase action at the micromolar level. Here we report a DNA binding study on these two ligands and a new derivative
2-(2-carboxy-4,5-dimethoxyphenyl0-6,7-dimethoxyisoquiloliniuminner salt (ligand III) in order to evaluate their binding selectivity to samples of nucleic acids (ssDNA, dsDNA, triplexes, and quadruplexes).
Simultaneous investigations on several DNA-ligand complexes carried out using an equilibrium dialysis approach revealed pronounced
binding selectivity of ligand I and ligand II to tetraplex DNA structures over the doublestranded DNA forms. 相似文献
18.
Blazej Gorzolnik Patrick Davidson Isabelle Beurroies Renaud Denoyel Daniel Grande 《Macromolecular Symposia》2010,287(1):127-134
Summary: Novel carboxy (COOH)-functionalized mesoporous polystyrene membranes were prepared from polystyrene-block-poly(D,L-lactide) (PS-b-PLA) diblock copolymers through the selective degradation of the PLA block. The combination of atom transfer radical polymerization (ATRP) and ring-opening polymerization (ROP) techniques enabled the synthesis of nanostructured diblock copolymers possessing carboxylic acid functionality at the junction between both blocks. Such copolymers were subjected to shear flow through the use of a channel die to align their nanodomains. Under mild alkaline conditions, the quantitative hydrolysis of the polyester nanodomains afforded mesoporous materials with COOH-coated pore walls. The PS-b-PLA precursors as well as the resulting porous systems were carefully analyzed by size exclusion chromatography (SEC), 1H NMR, scanning electron microscopy (SEM), and two-dimensional small-angle X-ray scattering (2-D SAXS). Moreover, the specific surface area and pore size distribution were determined by nitrogen sorption porosimetry. 相似文献
19.
A. Galatík und A. Blazej 《Colloid and polymer science》1978,256(6):616
Ohne Zusammenfassung 相似文献
20.
Blazej Scheibe Ewa Borowiak-Palen Ryszard J. Kalenczuk 《Journal of nanoparticle research》2011,13(11):5769-5780
This study presents the approach to the purification and subsequent metallic/semiconductive (M/S) fractionation of single-walled
carbon nanotubes (SWCNTs) with diameter from 1.04 to 1.60 nm produced via laser ablation. SWCNTs were purified through 3-fold
refluxing processes in nitric acid followed by the multiple washings with sodium hydroxide and hydrochloric acid. The purified-annealed
SWCNTs sample was divided into seven batches. One batch was dispersed in acetone as a reference sample. Each of the remaining
batches were dispersed in one of the following surface agents: sodium dodecyl sulfate, sodium cholate acid (SCA), sodium deoxycholate,
cetrimonium bromide, cetylpyridinium chloride, and benzalkonium chloride (BKC). SWCNT suspensions were fractionated via free
solution electrophoresis technique. The recovered fractions from electrode and control areas were analyzed via optical absorption
spectroscopy in UV–Vis–NIR range to evaluate the efficiency of the separation process. Raman spectroscopy was applied to analyze
the purity of the samples. The catalyst content was estimated by atomic absorption spectroscopy. The morphology of the investigated
samples was observed via high-resolution transmission electron microscopy. This contribution clearly shows that among the
investigated surfactants there are two promising candidates (SCA and BKC) which can efficiently enrich the bulk sample in
one electronic type of carbon nanotubes when FSE is applied. 相似文献