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991.
An Alignment Medium for Measuring Residual Dipolar Couplings in Pure DMSO: Liquid Crystals from Graphene Oxide Grafted with Polymer Brushes 下载免费PDF全文
Wen Zong Gao‐Wei Li Jiang‐Ming Cao Prof. Xinxiang Lei Prof. Mao‐Lin Hu Dr. Han Sun Prof. Christian Griesinger Prof. Ren Xiang Tan 《Angewandte Chemie (International ed. in English)》2016,55(11):3690-3693
Residual dipolar couplings (RDCs) have attracted attention in light of their great impact on the structural elucidation of organic molecules. However, the effectiveness of RDC measurements is limited by the shortage of alignment media compatible with widely used organic solvents, such as DMSO. Herein, we present the first liquid crystal (LC) based alignment medium that is compatible with pure DMSO, thus enabling RDC measurements of polar and intermediate polarity molecules. The liquid crystals were obtained by grafting polymer brushes onto graphene oxide (GO) using free radical polymerization. The resulting new medium offers several advantages, such as absence of background signals, narrow line shapes, and tunable alignment. Importantly, this medium is compatible with π‐conjugated molecules. Moreover, sonication‐induced fragmentation can reduce the size of GO sheets. The resulting anisotropic medium has moderate alignment strength, which is a prerequisite for an accurate RDC measurement. 相似文献
992.
Wanying He Xu Zheng Qi Zhao Lijie Duan Qiang Lv Guang Hui Gao Shuangjiang Yu 《Macromolecular bioscience》2016,16(6):925-935
A series of pH‐triggered charge‐reversal polyurethane copolymers (PS‐PUs) containing methoxyl‐poly(ethylene glycol) (mPEG), carboxylic acid groups, and piperazine groups is presented in this work. The obtained PS‐PUs copolymers can form into stable micelles at pH 7.4, which response to a narrow pH change (5.5–7.5) and show a tunable pH‐triggered charge‐reversal property. Doxorubicin (DOX) is encapsulated into the PS‐PU micelles as a model drug. The drug release of DOX‐loaded PS‐PU micelles shows an obviously stepped‐up with reducing the pH. Meanwhile, it is found that the charge‐reversal property can improve the cellular uptake behavior and intracellular drug release in both HeLa cells and MCF‐7 cells. Additionally, the time‐dependent cytotoxicity of the DOX‐loaded PS‐PU micelles is confirmed by MTT assay. Attributed to the tunable charge‐reversal property through changing the molar ratio of piperazine/carboxyl, the PS‐PU micelles will be a potential candidate as an intelligent drug delivery system in future studies.
993.
Gao Feng Ivan Djordjevic Vishal Mogal Richard O'Rorke Oleksandr Pokholenko Terry W. J. Steele 《Macromolecular bioscience》2016,16(7):1072-1082
Development of bioadhesive formulations for tissue fixation remains a challenge. The major drawbacks of available bioadhesives are low adhesion strength, toxic byproducts, and complexity of application onto affected tissues. In order to address these problems, this study has developed a hydrogel bioadhesive system based on poly amido amine (PAMAM) dendrimer, grafted (conjugated) with UV‐sensitive, 4‐[3‐(trifluoromethyl)‐3H‐diazirin‐3‐yl] benzyl bromide (PAMAM‐g‐diazirine). This particular diazirine molecule can be grafted to the surface amine groups of PAMAM in a one‐pot synthesis. Diazirine functionalities are carbene precursors that form covalent crosslinks with hydrated tissues after low‐power UV activation without necessity of free‐radical initiators. The rheological properties and adhesion strength to ex vivo tissues are highly controllable depending on diazirine grafting, hydrogel concentration, and UV dose intensity fitting variety types of tissues. Covalent bonds at the tissue/bioadhesive interface provide robust adhesive and mechanical strength in a highly hydrated environment. The free flowing hydrogel conversion to elastic adhesive after UV activation allows intimate contact with the ex vivo swine tissue surfaces with low in vitro cytotoxicity observed, making it a promising bioadhesive formulation toward clinical applications.
994.
pH Dependent Synthesis of NdIII Coordination Compounds Based on Bifunctional 5‐(4‐Pyridyl)tetrazole‐2‐acetic Acid 下载免费PDF全文
Meng Jie Cao Yue Kang Li Peng Peng Sun Chen Yi Zhang Jue Wang Qiao Yun Li Gao Wen Yang 《无机化学与普通化学杂志》2016,642(21):1218-1221
The NdIII coordination compounds [Nd(4‐pytza)3(H2O)2] · 2H2O ( 1 ) and [Nd(4‐pytza)2(H2O)4]Cl · 2H2O ( 2 ) [H4‐pytza = 5‐(4‐pyridyl)tetrazole‐2‐acetic acid] were synthesized by reactions of K4‐pytza and NdCl3 · 6H2O at different pH values. Single crystal X‐ray diffraction analysis reveals that 4‐pytza ligands in 1 in a μ1,3‐COO syn‐syn or μ1,1,3‐COO bridging mode coordinate to two central NdIII atoms to display a dinuclear unit, which is connected by one of these 4‐pytza ligands acting in end‐to‐end bridging mode to form a 1D ladder‐like chain. Different from 1 , each 4‐pytza in 2 with a μ1,3‐COO syn‐anti bridging mode coordinates to two NdIII atoms to display a 1D zigzag chain. Furthermore, the luminescence properties of 1 and 2 were investigated at room temperature in the solid state. 相似文献
995.
A strategy for monitoring and analyzing the chemical stability of Xuebijing injection (XBJ) by multiwavelength chromatographic fingerprints and multivariate classification techniques is presented in this paper. Multiwavelength chromatographic fingerprints were constructed using chromatographic data obtained at four wavelengths (260, 280, 320, and 400?nm). The raw chromatography data were preprocessed by noise reduction, baseline correction, data normalization, and interval correlation optimized shifting (icoshift). Using this method, fingerprints of 166 samples of XBJ subjected to different forced degradation conditions (irradiation, high temperature, and a range of pH values) were properly represented. Forty-one chemical components were identified using the iPeak program. In addition, the identified peak area profiling of chemical components were used for multivariate classification analysis. Principal component analysis (PCA) and Ward’s method were used to classify different XBJ degradation samples. The PCA score plot showed that XBJ degradation samples were clustered into four groups, and the results are confirmed by Ward’s method. Ten key chemical markers under different degradation conditions were found and identified by counterpropagation artificial neural networks (CP-ANN), statistical t-tests, and UPLC-Q-TOF-MS. The results suggest that the proposed strategy could be successfully applied to the comprehensive analysis of complex chemical systems. 相似文献
996.
Two novel heterocyclic diamine monomers: 1,2-dihydro-2-(4-aminophenyl)-4-[ 4-( 4-aminophenoxy) phenyl ]-(2H )-phtha-lazin-1-one and 1, 2-dihydro-2-( 4-aminophenyl )-4-[ 4-( 4-aminophenoxy) -3, 5-dimethylphenyl ] - (2H) -phthalazin-1-one were successfully synthesized using readily available heterocyclic bisphenol-like monomers through two steps in high yield. A series of novel poly( aryl ether amide)s containing the phthalazinone moiety with inherent viscosities of 1.16-1.67 dL/g were prepared by the direct polymerization of the novel diamines and aromatic dicarboxylic acids using triphenyl phosphite and pyridine as condensing agents. The polymers were readily soluble in a variety of solvents such as N, N-dimethyl-formamide (DMF), N,N-dimethylacetamide (DMAc), dimethylsulfoxide ( DMSO ), N-methyl-2-pyrrolidinone (NMP), and pyridine. The polymers had high glass transition temperatures (Tg) in the 291-329℃ range. 相似文献
997.
998.
A one-step pathway has been adopted to fabricate biodegradable polylactide (PLA) hollow spheres by interfacial polymerization
in an oil-in-water emulsion system. The mechanism of sphere formation is suggested with respect to interfacial cross-linking
polymerization and subsequent precipitation of the unreacted PLA macromonomers onto the preformed shells. Their hollow nature
and morphology were verified by transmission electron microscopy and scanning electron microscope characterizations. 相似文献
999.
X. F. Wang Y. F. Wang J. Wang Zh. H. Zhang J. Gao B. Liu Y. Ch. Jiang X. D. Zhang 《Russian Journal of Coordination Chemistry》2008,34(8):555-563
The title complexes, K3[Cd(Dtpa)] (H5Dtpa = diethylenetriamine-N,N,N,N′,N′-pentaacetic acid, (I)), K2[Cd(H2O)4][Cd(Edta)(H2O)]2 · 2H2O (H4Edta = ethylenediamine-N,N,N′,N′-tetraacetic acid, (II)), and Na2[Cd(H2O)4][Cd(Edta)(H2O)]2 · 2H2O (III), were prepared, and their compositions and structures were determined by elemental analyses, IR spectra, and single-crystal X-ray diffraction techniques, respectively. In complex I, the Cd is seven-coordinated by one Dtpa ligand yielding a pseudo-monocapped trigonal prism conformation, and the complex crystallizes in the triclinic crystal system with the Pi space group. The crystal data are as follows: a = 8.7300(17), b = 9.1200(18), c = 15.110(3) Å, α = 95.52(3)°, β = 96.59(3)°, γ = 99.63(3)°, V = 1170.0(4) Å3, Z = 2, ρ = 1.754 g/cm3, μ = 1.519 mm?1, F(000) = 616, R = 0.0644 and wR = 0.1712 for 3842 observed reflections with I ≥ 2σ(I). For complex II, in the [Cd(Edta)(H2O)]2? complex anion the Cd2+ ion is seven-coordinated by one Edta ligand and one water molecule, yielding a pseudo-pentagonal bipyramid conformation. In the [Cd(H2O)4]2+ cation, the bridged Cd is six-coordinated, yielding an almost standard octahedral conformation. The complex crystallizes in the monoclinic system with P21/n space group. The crystal data are as follows: a = 9.098(3), b = 16.442(6), c = 12.023(4) Å, β = 91.053(6)°, V = 1798.3(12) Å3, Z = 2, ρ = 2.098 g/cm3, μ = 2.086 mm?1, F(000) =1124, R = 0.0406 and wR = 0.1152 for 3680 observed reflections with I ≥ 2σ(I). In complex III, the conformations of Cd2+ ions are similar to those of the potassium salt complex, and the complex also crystallizes in the monoclinic crystal system with the P21/n space group. The crystal data are as follows: a = 9.134(7), b = 16.500(13), c = 12.075(10) Å, β = 91.054(12)°, V = 1820(2) Å3, Z = 2, ρ = 2.015 g/cm3, μ = 1.856 mm?1, F(000) = 1092, R = 0.0363 and wR = 0.0879 for 3707 observed reflections with I ≥ 2σ(I). 相似文献
1000.
Jinzhang Gao Haifeng Fan Wu Yang Xiangli Sun Chongyang Li Xuefeng Mao Jie Wang Rong Wang Zhengping Jia 《Central European Journal of Chemistry》2008,6(4):617-621
A rapid, simple and reliable capillary electrophoresis method for the separation and quantitation of inorganic cations with
indirect UV detection at 214 nm was developed. The electrolyte was: 12 mM imidazole as background absorbance provider; 5 mM
malic acid and 1.0 mM 18-crown-6 ether as complexing agents; and 20% D2O (v/v) to improve ion mobility. The pH was 4.25. The applied voltage was 22 kV at 22°C. Nine ions were completely separated
and determined with correlation coefficients of 0.9979-0.9992. The relative standard deviations (RSD) were less than 0.5%
for migration time and less than 5.2% for peak area (n=8). The detection limits (S/N=3) were from 0.08 mg L−1 (for Na+) to 0.51 mg L−1 (for Cu2+). To assess the reliability atomic absorption (AA) was also used to determine the same samples. Satisfactory results were
obtained for real samples of jasmine tea drink and coconut milk.
相似文献