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排序方式: 共有114条查询结果,搜索用时 31 毫秒
31.
32.
Aromatic hydrocarbons can be selectively recognized by four endo-functionalized molecular tubes through C/N-H...π interactions in nonpolar media with binding constants up to 1580 L/mol. 相似文献
33.
Erkki Aitola Arto Puranen Harri Setl Sami Lipponen Markku Leskel Timo Repo 《Journal of polymer science. Part A, Polymer chemistry》2006,44(22):6569-6574
Vinylcyclohexane (VCH) was copolymerized with ethene and propene using methylaluminoxane‐activated metallocene catalysts. The catalyst precursor for the ethene copolymerization was rac‐ethylenebis(indenyl)ZrCl2 ( 1 ). Propene copolymerizations were further studied with Cs‐symmetric isopropylidene(cyclopentadienyl)(fluorenyl)ZrCl2 ( 2 ), C1‐symmetric ethylene(1‐indenyl‐2‐phenyl‐2‐fluorenyl)ZrCl2 ( 3 ), and “meso”‐dimethylsilyl[3‐benzylindenyl)(2‐methylbenz[e]indenyl)]ZrCl2 ( 4 ). Catalyst 1 produced a random ethene–VCH copolymer with very high activity and moderate VCH incorporation. The highest comonomer content in the copolymer was 3.5 mol %. Catalysts 1 and 4 produced poly(propene‐co‐vinylcyclohexane) with moderate to good activities [up to 4900 and 15,400 kg of polymer/(mol of catalyst × h) for 1 and 4 , respectively] under similar reaction conditions but with fairly low comonomer contents (up to 1.0 and 2.0% for 1 and 4 , respectively). Catalysts 2 and 3 , both bearing a fluorenyl moiety, gave propene–VCH copolymers with only negligible amounts of the comonomer. The homopolymerization of VCH was performed with 1 as a reference, and low‐molar‐mass isotactic polyvinylcyclohexane with a low activity was obtained. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6569–6574, 2006 相似文献
34.
We demonstrate a proof-of-concept optical spectroscopic system for bioaerosol-particle fluorescence detection, in which a pulsed high-power laser is replaced by a highly compact linear array of sequentially fired light from blue light-emitting diodes. The results suggest that low-cost, compact optical aerosol detection may be feasible with the contemporary emergence of efficient UV light-emitting diodes. 相似文献
35.
ABSTRACTIn the solid state, uranyl-salophen complex 1, decorated with bipyridyl sidearms, self-assembles from moist acetonitrile into dimeric species displaying a confined water pentamer, as observed by X-ray diffraction on single crystals. The linear water cluster is incarcerated within the dimeric cavity by coordination to the Lewis acidic uranyl centres and by a network of hydrogen bonds established with the pyridinic nitrogen atoms on the sidearms. 相似文献
36.
Vuorimaa E Urtti A Seppänen R Lemmetyinen H Yliperttula M 《Journal of the American Chemical Society》2008,130(35):11695-11700
Cationic polymers bind DNA and form compacted nanoparticulates (i.e., polyplexes). Polyplexes augment DNA delivery into the cells as a nonviral method of gene therapy. DNA packing and release are the key factors in polyplex-mediated gene delivery, but they are poorly understood due to the lack of physical methods of investigation. We used time-resolved fluorescence spectroscopy to study poly(ethylenimine) (PEI) and poly(L-lysine) (PLL) polyplexes. Analysis of fluorescence lifetimes and time-resolved spectra revealed that DNA exists in several different states in PEI polyplexes and only in one tightly bound state in PLL polyplexes. The observed difference in the nature of the polyplexes may explain why PEI releases DNA more easily than PLL even though both polycations condense DNA effectively. The present method utilizing time-resolved fluorescence spectroscopy gives information on the specific interactions between DNA and the cationic polymers in the polyplexes. This kind of information is very important in the development of biologically effective nonviral systems for DNA delivery. 相似文献
37.
Monitoring of Saccharomyces cerevisiae cell proliferation on thiol-modified planar gold microelectrodes using impedance spectroscopy 总被引:1,自引:0,他引:1
Heiskanen AR Spégel CF Kostesha N Ruzgas T Emnéus J 《Langmuir : the ACS journal of surfaces and colloids》2008,24(16):9066-9073
An impedance spectroscopic study of the interaction between thiol-modified Au electrodes and Saccharomyces cerevisiae of strain EBY44 revealed that the cells formed an integral part of the interface, modulating the capacitive properties until a complete monolayer was obtained, whereas the charge transfer resistance ( R ct) to the redox process of [Fe(CN)6] 3-/4- showed a linear relationship to the number of cells even beyond the monolayer coverage. R ct showed strong pH dependence upon increasing the pH of the utilized buffer to 7.2. Upon addition of S. cerevisiae cells at pH 7.2, the obtained value of R ct showed over 560% increase with respect to the value obtained on the same thiol-modified electrode without cells. It was demonstrated that real-time monitoring of S. cerevisiae proliferation, with frequency-normalized imaginary admittance (real capacitance) as the indicator, was possible using a miniaturized culture system, ECIS Cultureware, with integrated planar cysteamine-modified Au microelectrodes. A monolayer coverage was reached after 20-28 h of cultivation, observed as an approximately 15% decrease in the real capacitance of the system. 相似文献
38.
Coordinatively Unsaturated Lanthanide(III) Helicates: Luminescence Sensors for Adenosine Monophosphate in Aqueous Media
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Jashobanta Sahoo Rajendran Arunachalam Dr. Palani S. Subramanian Dr. Eringathodi Suresh Dr. Arto Valkonen Prof. Dr. Kari Rissanen Prof. Dr. Markus Albrecht 《Angewandte Chemie (International ed. in English)》2016,55(33):9625-9629
Coordinatively unsaturated double‐stranded helicates [(H2L)2Eu2(NO3)2(H2O)4](NO3)4, [(H2L)2Tb2(H2O)6](NO3)6, and [(H2L)2Tb2(H2O)6]Cl6 (H2L=butanedioicacid‐1,4‐bis[2‐(2‐pyridinylmethylene)hydrazide]) are easily obtained by self‐assembly from the ligand and the corresponding lanthanide(III) salts. The complexes are characterized by X‐ray crystallography showing the helical arrangement of the ligands. Co‐ligands at the metal ions can be easily substituted by appropriate anions. A specific luminescence response of AMP in presence of ADP, ATP, and other anions is observed. Specificity is assigned to the perfect size match of AMP to bridge the two metal centers and to replace quenching co‐ligands in the coordination sphere. 相似文献
39.
40.
Leskinen MV Yip KT Valkonen A Pihko PM 《Journal of the American Chemical Society》2012,134(13):5750-5753
The dehydrogenative β'-functionalization of α-substituted β-keto esters with indoles proceeds with high regioselectivities (C3-selective for the indole partner and β'-selective for the β-keto ester) and good yields under mild palladium catalysis at room temperature with a variety of oxidants. Two possible mechanisms involving either late or early involvement of indole are presented. 相似文献