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951.
Xin‐Wei Cao Jun Li Si‐Bao Chen Xiao‐Bo Li Pei‐Gen Xiao Shi‐Lin Chen Da‐Jian Yang 《Journal of separation science》2010,33(11):1587-1594
A sensitive and reliable HPLC‐diode‐array detector method was developed for the first time to simultaneously determine nine nucleosides and nucleobases including uracil, cytidine, guanine, uridine, thymine, inosine, guanosine, thymidine and adenosine in 13 different Fritillaria species. The analysis was performed on a BaseLine C18 column with a gradient of acetonitrile in water at a flow rate of 0.8 mL/min. The diode‐array detector wavelength was set at 260 nm for the UV detection of nucleosides and nucleobases. Satisfactory separation of these compounds was obtained in less than 40 min. The optimized method provided good linear relation (r2 >0.9995 for all the investigated analytes), satisfactory precision (RSD <1.51%) and good recovery (from 97.64 to 101.16%). The established method was successfully applied to simultaneous determination of nine nucleosides and nucleobases in 61 batches of samples from 13 Fritillaria species collected from different habitats in China, which could be helpful to control the quality of Fritillaria bulbs. 相似文献
952.
Surface functionalization of the plasma‐pretreated polycarbonate (PC) track‐etched membranes via plasma‐induced thermally graft copolymerization of acrylic acid (AAc) was carried out. The resulting PC membranes with grafted AAc side chains were characterized by X‐ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric (TG) analysis. The morphology of the PC membranes was studied by scanning electron microscopy (SEM). The results showed that the grafted PAAc polymers were formed uniformly inside the pores throughout the entire membrane thickness. With increase in the pore‐filling ratio, the pore diameters of PAAc‐grafted membranes became smaller. The PC‐g‐PAAc membranes exhibit rapid and reversible response of the flux to the environmental pH as pH is switched between 3 and 9. Between pH 3.5 and 5.5, the membranes demonstrate a pH‐valve function as the carboxyl group changes from neutral to charged with a corresponding variation in chain configuration. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
953.
Hollow α-Fe2O3 nanospheres were synthesized by using novel carbon spheres as templates. By carefully controlling the fundamental experimental parameters, porous nanospheres with diameters of 60–80 nm and nanojujubes with diameters of 80–100 nm have been efficiently obtained, respectively. The growth mechanism and magnetic properties are also discussed in detail. The coercivity values of the hollow α-Fe2O3 nanospheres and nanojujubes are much higher than those of other α-Fe2O3 nanomaterials. Due to the unique morphology with cavum and porous wall, the ferromagnetic nanospheres could be promising candidates as a magnetic carrier for drug targeting. 相似文献
954.
955.
A pcu network can be ordered through trigonal bipyramidal nanocages as secondary building blocks, which have the striking feature of hydrophilic affinity to the polar molecules and π-π interactions for aromatic molecules. 相似文献
956.
The first asymmetric synthesis of indole alkaloid (+)-subincanadine F was successfully accomplished with the uncommon 7-endo-trig stereoselective radical cyclization as the key step and its absolute configuration was thus assigned. 相似文献
957.
958.
以17α-炔雌二醇和17β-雌二醇为原料,分别与烯丙基溴、溴代异戊烯反应,通过一步反应合成了4个新雌激素衍生物,分别是17α-炔雌二醇-3-烯丙基醚(ES-1),17β-雌二醇-3-烯丙基醚(ES-2),17α-炔雌二醇-3-异戊烯基醚(ES-3)和17β-雌二醇-3-异戊烯基醚(ES-4),产率分别为92.2%,73.7%,65.9%和67.6%.化合物通过1HNMR,13CNMR,IR,MS及元素分析确证了结构,4个化合物均未见文献报道.初步的抗辐射升白生物活性研究表明,4个化合物对137Csγ-射线引起的小鼠白细胞低下及造血系统功能损伤有一定的保护作用.其中ES-3的升白作用最佳,经统计学处理,3个给药剂量组与对照组比,升白作用均有非常显著性差异(P0.001). 相似文献
959.
Hybrid chips combing microchips with capillaries have displayed particular advantages in achieving UV-vis and mass spectroscopic detection. In this work, systematic 3-D numerical simulations have been carried out to explore the influence of junction interface cross-sectional area and ζ-potential distribution on sample band broadening in hybrid-chip electrophoresis separation. In this case, the ratio of cross-sectional area of chip to capillary channel (S(ratio) ) is used as the parameter of the variation in junction interface cross-sectional area. Theoretical simulations demonstrated that the decrease of the S(ratio) would increase the separation efficiency in the hybrid-chip-based CE with uniform ζ-potential distribution. ζ-potential distribution along the axial direction of the channel also affects mass transport in hybrid-chip-based CE. Therefore, the effect of ζ-potential distribution has been considered in the 3-D simulation. Theoretical simulation results reveal that ζ-potential distribution rather than the interface cross-sectional area variation (S(ratio) ) controls the sample band broadening and manipulates sample separation efficiency in the hybrid-chip-based CE with non-uniform ζ-potential distribution. Both the theoretical simulations and experimental results show that optimal hybrid-chip CE separation efficiency can be achieved at S(ratio) =1. 相似文献
960.
The creation of tailor-made receptors which are able to recognize molecular targets with high affinity and selectivity has
attracted much attention in the field of chemistry, physics, and biology. Molecular imprinting has proved to be an effective
technique for generating specific recognition sites in synthetic polymers. The synthesis of molecular imprinted polymers specific
for proteins and peptides has been a focus for many scientists working in the area of molecular recognition, since the creation
of synthetic polymers that can specifically recognize biomacromolecules is a very challenging but potentially extremely rewarding
work. These polymers with specificity for biological macromolecules have considerable potential for applications in the areas
of solid phase extraction, catalysis, medicine, clinical analysis, drug delivery, environmental monitoring, and sensors. In
this review, the authors discuss the developed approaches associated with the imprinting of peptides and proteins, and provide
an overview of the significant progress achieved within this field. Finally, the possible mechanism of the molecular imprinting
and recognition has been discussed. 相似文献