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161.
A new method is applied to prepare stable aqueous dispersion of magnetic iron oxide nanoparticles (MNPs) by biocompatible maleate polymers. Fe3O4 magnetic core–shell nanoparticles are obtained via forming an inclusion complex between carboxylic acid groups of maleated biocompatible polymers shell and Fe3O4 MNPs core surface. Maleate polymers are synthesized via esterification of poly(ethylene glycol), poly(vinyl alcohol) and starch with maleic anhydride (MA). The Fe3O4 magnetic core–shell nanoparticles are characterized by Fourier transform infrared spectroscopy, X‐ray diffraction, transmission electron microscopy and vibrating sample magnetometer. The obtained magnetic core–shell nanoparticles exhibit superparamagnetic property and reveal long‐term aqueous stability. This work represents a valid methodology to produce highly stable aqueous dispersion of Fe3O4 MNPs ferrofluids which can be expected to have great potential as contrast agent for magnetic resonance imaging. Furthermore, the shell composition of biocompatible maleate polymers with double bond of MA as crosslinker agent allows the polymerization with other monomers to design preferred drug delivery systems. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
162.
Development of highly functional cesium selective adsorbents for the decontamination of high-activity-level water(HALW) from the Fukushima NPP-1 accident is very urgent. In order to selectively adsorb the radioactive cesium, three kinds of novel porous silica gels loaded with insoluble ferrocyanides(SLFC) were prepared using a successive impregnation/precipitation method. Based on the results of previous research, the SLFC composites have relatively large uptake ratio above 95%, distribution coefficients(Kd) above 103 cm3/g, and excellent adsorption kinetics even in seawater. The solidification results also indicate that zeolites have an excellent Cs immobilization characteristic, gas-trapping and self-sintering abilities, and low leachability. We chose three kinds of SLFC composites to achieve the optimization of solidification by mixing with nine kinds of additives at high temperatures(up to 1200 °C). The Cs contents in the three composites were estimated to be below 30% of the initial contents and decreased with the three stages at calcination temperatures ranging from 25 to 1200 °C. By contrast, the Cs immobilization ratio was markedly lowered by mixing with additives: of those, allophane had the best immobilization result. By increasing the additive ratio to 50 wt%, the Cs immobilization ratio became almost 100% and no volatilization of Cs was detected even after calcination at 1200 °C. This result indicates that calcination of the mixture of SLFC composites after adsorbing Cs+ ions and specific additives under appropriate ratio is effective for stable solidification. 相似文献
163.
164.
The demand for more efficient methods of establishing the undetermined stereochemistries of peptidic natural products continues unabated. A new method for microscale stereochemical determination was devised by integrating solid-phase synthesis, split-and-mix randomization, 18O/16O-encoding of d /l -configurations, tandem mass spectrometry, and biological evaluation. Here we applied gramicidin A as the molecule for a blind test. Gramicidin A and its 31 diastereomers were randomly prepared in microgram scale with 18O/16O-stereochemical encoding and subjected to MS/MS-structural determination and cytotoxicity assay. Only the parent gramicidin A was selected from among the 32 stereoisomers, validating the high reliability of the present strategy. 相似文献
165.
166.
Guo-Qiang Tang Xian-Hua Li Qiu-Li Li Yu Liu Xiao-Xiao Ling 《Surface and interface analysis : SIA》2020,52(5):190-196
Carbonate oxygen (O) and carbon (C) isotopes are widely used as proxies for tracing the processes and physicochemical conditions of many geological events and environmental changes in Earth Science. In particular, O and C isotopic variations at micrometer scales revealed by modern microbeam analytical techniques such as SIMS and NanoSIMS are robust archives for reconstructing palaeoenvironment and paleoclimate changes at annual and seasonal resolution or even higher temporal resolution. Widespread application of carbonate O and C isotopic microanalysis in Earth Sciences, however, has been restricted due to limitation of high-quality carbonate reference materials for O and C isotopic microanalysis. We introduce in this paper a new calcite reference material for calcite O and C isotopic microanalysis. This calcite is collected from a drill-core of the Oka carbonatite complex (Quebec, Canada). We demonstrated that the Oka calcite is fairly homogeneous in O and C isotopic compositions at micrometer scales based on homogeneity test by hundreds of SIMS O and C isotopic analyses. Precise determinations by using conventional gas-source IRMS yield the recommended value of δ18OVPDB = −23.12 ± 0.15‰ (1SD) and δ13CVPDB = −5.23 ± 0.06‰ (1SD) for the Oka calcite, which has been certified as the first class of Chinese national certified reference material (GBW04481) for O and C isotopic microanalysis. 相似文献
167.
毛细管电泳经常遭受结果不稳定、不重现的困扰。该文从理论上推导了一些新模式并以例证说明,这些模式能在一定条件下抵抗条件变化,获得超重现电泳谱图。它们是加权淌度谱、迁移电量谱、电荷密度谱、摩尔电荷密度谱、扩散系数谱、液相质量谱,以及它们各自的比例谱等,其中前4种为实时测量模式,其余的为实验后模式。这些模式需要发展新的仪器或算法,但都有发展潜力,值得深入研究。 相似文献
168.
Eder Toms‐Mendivil Marc Devillard Vianney Regnier Jacques Pecaut David Martin 《Angewandte Chemie (International ed. in English)》2020,59(28):11516-11520
Oxyallyl derivatives are typically elusive compounds. Even recently reported “stabilized” 1,3‐diaminooxyallyl species are still highly reactive and have short lifetimes at room temperature. Herein, we report the synthesis and preliminary study of mesoionic pyrimidine derivatives that feature 1,3‐bis(dimethylamino)oxyallyl patterns with an unprecedented level of stabilization. The latter are not only insensitive towards air and moisture, but they are also compatible with the formation of an ancillary stable N‐heterocyclic carbene moiety. As the oxyallyl pattern is proton‐responsive, it allows the reversible switching of the electronic properties of the carbene, as a ligand. 相似文献
169.
Felix Nußbaumer Raphael Plangger Manuel Roeck Christoph Kreutz 《Angewandte Chemie (International ed. in English)》2020,59(39):17062-17069
We present the access to [5‐19F, 5‐13C]‐uridine and ‐cytidine phosphoramidites for the production of site‐specifically modified RNAs up to 65 nucleotides (nts). The amidites were used to introduce [5‐19F, 5‐13C]‐pyrimidine labels into five RNAs—the 30 nt human immunodeficiency virus trans activation response (HIV TAR) 2 RNA, the 61 nt human hepatitis B virus ? (hHBV ?) RNA, the 49 nt SAM VI riboswitch aptamer domain from B. angulatum, the 29 nt apical stem loop of the pre‐microRNA (miRNA) 21 and the 59 nt full length pre‐miRNA 21. The main stimulus to introduce the aromatic 19F–13C‐spin topology into RNA comes from a work of Boeszoermenyi et al., in which the dipole‐dipole interaction and the chemical shift anisotropy relaxation mechanisms cancel each other leading to advantageous TROSY properties shown for aromatic protein sidechains. This aromatic 13C–19F labeling scheme is now transferred to RNA. We provide a protocol for the resonance assignment by solid phase synthesis based on diluted [5‐19F, 5‐13C]/[5‐19F] pyrimidine labeling. For the 61 nt hHBV ? we find a beneficial 19F–13C TROSY enhancement, which should be even more pronounced in larger RNAs and will facilitate the NMR studies of larger RNAs. The [19F, 13C]‐labeling of the SAM VI aptamer domain and the pre‐miRNA 21 further opens the possibility to use the biorthogonal stable isotope reporter nuclei in in vivo NMR to observe ligand binding and microRNA processing in a biological relevant setting. 相似文献
170.
The saline lacustrine deposit of the Oligocene Lower Ganchaigou Formation is the main source rock for the Western Qaidam Basin,NW China.In this study,abundant highly branched isoprenoids with 25 carbon atoms (C25HBI) were detected in the upper section of the Lower Ganchaigou Formation.C25HBI is a biomarker for diatoms,and can provide information regarding biogeochemical processes during production and preservation of sedimentary organic matter.The carbon isotopic values of C25HBI in these source rocks were in the range of-18‰ to-20‰.The relative enrichment in 13C of C25HBI suggests that these isoprenoids were derived from diatom blooms.In this case,the diatoms used HCO3-as an additional carbon source to dissolved CO2 in water column due to their high biological productivity.Conversely,the diatom blooms indicated an abundant nutrient supply to the environment and high primary productivity.Thus,the occurrence of 13C-enriched C25HBI could be an ideal marker for good source rocks.The decreased concentration of CO2(aq) in the water column induced by diatom blooms can result in an enrichment in 13C of organic matter synthesized by primary producers.This may be a possible reason for the occurrence of 13C-enriched organic matter in the Cenozoic source rocks of the Western Qaidam Basin.Previous studies have shown that the high carbon number n-alkanes sourced from diatoms have no carbon preference.Hence,the sources of n-alkanes in regional source rocks are complex,and should be considered when discussing the sources of organic matter in future studies. 相似文献