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101.
The total synthesis of isomer of didemnaketal A was achieved in 26 steps. The position of esters is switched at C7 and C8 with respect to their proposed position in natural didemnaketal A, which shows potent anti-HIV activity but so far has not been synthesized in the laboratory. Structural analysis of synthetic isomer of didemnaketal A indicates that the esters at C7 and C8 are correctly assigned, suggesting that the problems for the structural reassignment of natural didemnaketal A lie elsewhere.  相似文献   
102.
In this paper, we study the Heinz type inequalities for mappings satisfying Poisson’s equation. Some results generalize the ones obtained by Partyka and Sakan.  相似文献   
103.
A new star-shaped molecule StOF-Br_3 containing oligofluorenes and halogen atoms(Bromine) has been synthesized and studied by Scanning Tunneling Microscopy(STM) at the highly oriented pyrolytic graphite(HOPG) surface.We have obtained the high-resolution self-assembled STM images,from which the highly ordered and closely packed non-porous arrangements of the StOF-Br_3 molecular selfassemblies at the heptanoic acid/HOPG surface could be observed.The molecular models and selfassembled StOF-Br_3 architectures have been given in the following text.Besides,we have also figured out the surface free energy by the density functional theory(DFT) calculation,which proved that the halogen...halogen interaction was strong enough to stabilize the ordered molecular self-assemblies.This work verifies the existence of bromine...bromine interactions,and meanwhile provides a kind of effective approach for quickly building ordered molecular nanoarchitectures with large areas and different geometries.  相似文献   
104.
A colorimetric Al3+ sensor based on fluorescence recovery of a conjugated copolymer-ATP complex is proposed. An optimized ratio of two polythiophene (PT) monomers is utilized to synthesize copolymer (CP) that yielded maximized colorimetric response for Al3+ in deionized (DI) and tap water. The electrostatic disassembly of CP-ATP upon addition of Al3+ led to an evident visual color change. The lowest concentration of Al3+ for naked eye observation is around 4 μM, which is below the threshold levels in drinking water according to European Economic Community (EEC) standard. Besides, the proposed assay showed a similar response to Al3+ in tap water. The proposed methodology showed selective and sensitive detection for Al3+ in analytically relevant concentration ranges without involving sophisticated instrumentation, illustrating the applicability for on-site drinking water monitoring.  相似文献   
105.
Wang  Xiwen  Liu  Suqin  Wang  Haiyan  Tu  Feiyue  Fang  Dong  Li  Yanhua 《Journal of Solid State Electrochemistry》2012,16(11):3593-3602
Journal of Solid State Electrochemistry - A series of Co3O4 nanoplates/graphene nanosheets (GNS) composites are fabricated using a facile and green method by hydrothermal treatment and subsequent...  相似文献   
106.
A biocompatible complex has been prepared as gene carrier via electrostatic interaction, which is composed of a polycation, that is, poly[(dimethylamino)ethyl methacrylate] end-capped with cholesterol moiety (Chol-PDMAEMA30), along with a polyanion named poly(aspartic acid)-grafted-poly(ethylene glycol) (PASP-g-PEG). The complexes have less cytotoxicity compared to the case of alone Chol-PDMAEMA30 or branched polyethylenimine (PEI) system.

In the present study, biocompatible complexes have been prepared as gene carrier via electrostatic interaction, which is composed of a polycation, that is, poly[(dimethylamino)ethyl methacrylate] end-capped with cholesterol moiety (Chol-PDMAEMA30), along with a polyanion named poly(aspartic acid)-grafted-poly(ethylene glycol) (PASP-g-PEG). We first synthesized polysuccinimide (PSI) via condensation polymerization of aspartic acid, and then used PEG-NH2 to react with the partial pentacyclic rings of PSI to yield a kind of graft copolymer polysuccinimide-grafted-poly(ethylene glycol) (PSI-g-PEG). After hydrolysis of the residual succinimide units, a new biodegradable and biocompatible graft copolymer PASP-g-PEG was prepared successfully. Chol-PDMAEMA30 was synthesized via oxyanion-initiated polymerization, as reported in our previous literature. We investigated the interactions between every pair among calf thymus DNA, Chol-PDMAEMA30, and PASP-g-PEG by agarose gel retardation assay. The results indicate that the prepared complexes could completely bind DNA and may become more stable during systemic circulation. The complexes have less cytotoxicity compared to the case of alone Chol-PDMAEMA30 or branched polyethylenimine (PEI) system. Furthermore, the physicochemical properties of the complexes were also investigated by zeta potential, transmission electron microscopy (TEM) and dynamic light scattering (DLS) measurements. These biodegradable and biocompatible polymeric carriers have potential applications in gene delivery.  相似文献   
107.
Four cone calix[4]arene-1,2-crown ethers each with two ionisable side arms containing dansyl groups are synthesised. The crown ether ring on the lower rim is varied from crown-4 to crown-5 with hydrogen or tert-butyl groups on the para position of the upper rim. Di(tetramethylammonium) salts of the di-ionised ligands are utilised for spectrofluorimetric titration experiments in MeCN. The influence of alkali metal, alkaline earth metal and selected transition and heavy metal (Co2+, Fe2+, Hg2+, Mn2+, Pb2+, Zn2+ and Fe3+) cations on the spectroscopic properties of the two dansyl groups linked to the lower rim of the conformationally locked, di-ionised calix[4]arene-1,2-crown ether frameworks is investigated by emission spectrophotometry. All of the metal cations induce red shifts in the emission spectra of the di-ionised ligands. The metal cations produce enhancement or quenching of the fluorescence emissions. Changes in the fluorescence emission as a function of the metal cation identity, the lower rim crown ether ring size and the absence or presence of upper rim tert-butyl groups are investigated.  相似文献   
108.
109.
Concise and efficient three‐component domino [4+1+1] carbocyclization to highly substituted fluoren‐9‐one derivatives promoted by K2CO3 has been developed under microwave irradiation conditions. The direct bis‐cyanation and aryl amination residing in fluoren‐9‐one framework were achieved in a one‐pot operation. The reaction proceeds at fast rates and can be finished within 30 min, which makes workup convenient to give good to excellent chemical yields.  相似文献   
110.
To investigate long-term CO2 behavior in geological formations and quantification of possible CO2 leaks, it is crucial to investigate the potential mobility of CO2 dissolved in brines over a wide range of spatial and temporal scales and density distributions in geological media. In this work, the mass transfer of aqueous CO 2 in brines has been investigated by means of a chemical potential gradient model based on non-equilibrium thermodynamics in which the statistical associating fluid theory equation of state was used to calculate the fugacity coefficient of CO2 in brine. The investigation shows that the interfacial concentration of aqueous CO2 and the corresponding density both increase with increasing pressure and decreasing temperature; the effective diffusion coefficients decrease initially and then increase with increasing pressure; and the density of the CO2 -disolved brines increases with decreasing CO2 pressure in the CO2 dissolution process. The aqueous CO2 concentration profiles obtained by the chemical potential gradient model are considerably different from those obtained by the concentration gradient model, which shows the importance of considering non-ideality, especially when the pressure is high.  相似文献   
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