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排序方式: 共有1336条查询结果,搜索用时 15 毫秒
201.
Huang H Zhang J Chen G Lu Z Wang X Sha N Shao B Li P Guo DA 《Biomedical chromatography : BMC》2008,22(4):421-427
A sensitive and simple HPLC method has been developed and validated for the determination of oxyresveratrol (trans-2,4,3',5'-tetrahydroxystilbene, OXY) and resveratrol (trans-3,5,4'-trihydroxystilbene, RES) in rat plasma. The plasma samples were extracted with ethyl acetate and analyzed using HPLC on an Aglient Zorbax SB-C(18) column (250 x 4.6 mm, 5 microm) at a wavelength 320 nm, with a linear gradient of (A) acetonitrile and (B) 0.5% aqueous acetic acid (v/v), at a flow rate of 1.0 mL/min. The method was linear over the range of 0.1265-25.3 microg/mL for OXY and 0.117-23.4 microg/mL for RES. The extraction recovery for OXY, RES and internal standard ranged from 71.1 to 88.3%. The intra- and inter-day precisions were better than 10%, and the accuracy ranged from 89 to 108%. The validated method was used to study the pharmacokinetic profiles of OXY and RES in rat plasma after oral administration of Smilax china root extract. 相似文献
202.
Miao Zhu Qin Zhou He Cheng Prof. Dr. Ye Sha Prof. Dr. Vladimir I. Bregadze Prof. Dr. Hong Yan Prof. Dr. Zhe Sun Prof. Dr. Xiang Li 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2023,135(1):e202213470
The combination of carbon-based nanohoops with other functional organic molecular structures should lead to the design of new molecular configurations with interesting properties. Here, necklace-like nanohoops embedded with carborane were synthesized for the first time. The unique deboronization of o-carborane has led to the facile preparation of ionic nanohoop compounds. Nanohoops functionalized by nido-o-carborane show excellent fluorescence emission, with a solution quantum yield of up to 90.0 % in THF and a solid-state quantum efficiency of 87.3 %, which opens an avenue for the applications of the nanohoops in OLEDs and bioimaging. 相似文献
203.
Dr. Peng Luo Dr. Xue-Jing Zhai Dr. Sha Bai Dr. Yu-Bing Si Dr. Xi-Yan Dong Prof. Dr. Ying-Feng Han Prof. Dr. Shuang-Quan Zang 《Angewandte Chemie (International ed. in English)》2023,62(22):e202219017
Chiral Au nanoclusters have promising application prospects in chiral sensing, asymmetric catalysis, and chiroptics. However, enantiopure superatomic homogold clusters with crystallographic structures emitting bright circularly polarized luminescence (CPL) remain challenging. In this study, we designed chiral N-heterocyclic carbenes (NHCs), and for the first time enantioselectively synthesized a pair of monovalent cationic superatomic Au13 clusters. This new enantiomeric pair of clusters has a quasi-C2 symmetric core and exhibited CPL with an unprecedent solution-state quantum yield (QY) of 61 % among those of the atomically precise Au nanoclusters. DFT calculations provided insights into the circular dichroism behavior, and revealed the origin of CPL from superatomic Au clusters. This work opens a new avenue for developing novel homochiral nanoclusters using chiral NHC ligands and provides fundamental understanding of the origin of the chiroptics of metal clusters. 相似文献
204.
Liu Y Kuzuya A Sha R Guillaume J Wang R Canary JW Seeman NC 《Journal of the American Chemical Society》2008,130(33):10882-10883
We describe the synthesis of a hybrid DNA/organic macrocycle that is prepared by formation of an amide linkage across one full turn of DNA. Formation of a catenane proved that the linkage crossed a turn rather than running along the phosphodiester backbone contour. The product, a doubly tailed catenane, contains 5'- and 3'-termini that can be functionalized further or used to incorporate the catenane structure into other DNA assemblies. 相似文献
205.
Assembly of the highest connectivity Wells-Dawson polyoxometalate coordination polymer: the use of organic ligand flexibility 总被引:2,自引:0,他引:2
Tian AX Ying J Peng J Sha JQ Han ZG Ma JF Su ZM Hu NH Jia HQ 《Inorganic chemistry》2008,47(8):3274-3283
Through tuning the length of flexible bis(triazole) ligands and different metal ion coordination geometries, four Wells-Dawson polyoxoanion-based hybrid compounds, [Cu 6(btp) 3(P 2W 18O 62)].3H 2O ( 1) (btp = 1,3-bis(1,2,4-triazol-1-y1)propane), [Cu 6(btb) 3((P 2W 18O 62)].2H 2O ( 2), [Cu 3(btb) 6(P 2W 18O 62)].6H 2O (btb = 1,4-bis(1,2,4-triazol-1-y1)butane) ( 3), and [Cu 3(btx) 5.5((P 2W 18O 62)].4H 2O (btx = 1,6-bis(1,2,4-triazol-1-y1)hexane) ( 4), were synthesized and structurally characterized. In compound 1, the metal-organic motif exhibits a ladder-like chain, which is further fused by the ennead-dentate [P 2W 18O 62] (6-) anions to construct a 3D structure. In compound 2, the metal-organic motif exhibits an interesting Cu-btb grid layer, and the ennead-dentate polyoxoanions are sandwiched by two Cu-btb layers to construct a 3D structure. Compound 3 exhibits a (4 (2).6 (2).8 (2)) 3D Cu-btb framework with square and hexagonal channels arranged alternately. The hexa-dentate polyoxoanions incorporate only into the hexagonal channels. In compound 4, there exist two sets of (6 (1).10 (2)) 2(6 (1).8 (2).10 (3)) 3D Cu-btx frameworks to generate a 2-fold interpenetrated structure into which the penta-dentate polyoxoanions are inserted to construct a 3D structure. The structural analyses reveal that the length of flexible bis(triazole) ligands and metal ion coordination geometries have a synergic influence on the structures of this series. To our knowledge, they have the highest connectivity for the Wells-Dawson polyoxometalate coordination polymers to date. 相似文献
206.
铈在水鳖叶片内的分布及生理和结构效应分析 总被引:3,自引:1,他引:2
以分布广泛的高等浮水植物--水鳖为研究对象,在人工模拟的含不同浓度Ce的水溶液中培养7 d,研究了Ce在水鳖叶细胞中的分布及其结构和生理效应. 随着Ce浓度的增大,水鳖叶片褪绿程度逐渐加重,光合色素(叶绿素和类胡萝卜素)含量也显著下降. Ce对保护酶系统存在不同影响,分别在2.5和5 mg·L-1时诱导SOD和POD活性达峰值,其后逐渐下降,但POD活性都高于对照,SOD则受到明显抑制,而CAT活性一直呈上升趋势. Ce导致可溶性糖在水鳖叶片内显著积累. 可溶性蛋白含量在2.5 mg·L-1 Ce时最大,比对照增加了12.98%,其后则下降并与Ce浓度显著负相关. SDS-PAGE电泳表明,当Ce浓度大于2.5 mg·L-1后,分子量为141.9,54.8和15.8 kD的蛋白/多肽表达逐渐减弱,但同时诱导出了分子量为33.0和20.7 kD的新蛋白. 电镜观察发现Ce对叶绿体、线粒体和细胞核的结构造成明显损伤,主要是被膜或外膜破裂和核质消失. 定位结果显示Ce主要分布在细胞壁以及细胞壁和质膜之间,原生质体内部没有观察到. 结果表明,(1)Ce不仅损害了水鳖的生理活性,而且也破坏了细胞的超微结构,最终导致植物死亡. (2)光合色素是反应最敏感的生理指标. (3)在实验周期内,Ce对水鳖的半效应浓度(EC50)为10 mg·L-1,水体最大允许浓度为1 mg·L-1. 相似文献
207.
208.
Wen-Bo Lan Sha Gao Ying-Wu Lin Guo-Wen Peng 《Journal of Coordination Chemistry》2016,69(18):2775-2784
Uranyl–salophen (U–S) complexes, as modified by unilateral benzene and coordinated with cyclohexenones substituted by methyls or fluorines in E/Z-types, were investigated using density functional theory calculations at the level of B3LYP/6–311G** basis set. The results indicated that the O of substituted cyclohexenones could coordinate with U of the asymmetric U–S complexes. When the C=C bond of cyclohexenones was located upward in the twisted salophen plane, the binding energies of the cyclohexenones to the asymmetric U–S and Wiberg bond indices (WBIs) of carbonyl oxygen to uranium (U–O) were higher than those of the C=C bonds located downward. It could be concluded that when cyclohexenones were coordinated to the asymmetric U–S, the major products would be the complexes in which the C=C bond of cyclohexenones locates upward in the configuration. Binding energies of the E-type substituted cyclohexenones to the asymmetric U–S were higher than those for the Z-type ones. 相似文献
209.
A discovery that the inexpensive Br2 can serve as a potent Lewis acid catalyst for bis(2-hydroxy-1-naphthyl)methanes synthesis is presented. Under the catalysis of Br2 at room temperature, naphthols reacted smoothly with various aldehydes with high efficiency and broad substrate scope. This reaction used to require highly acidic conditions and/or high temperature and/or pressure, and sometimes featured poor yields. Moreover, theoretical calculations suggested that Br2 is a potent Lewis acid to activate the carbonyl group, yet it was not the primary cause for the remarkable activity of Br2 in the current communication. 相似文献
210.
研究了一类具有逐项分数阶导数的微分方程边值问题.对参数的各种取值情况进行了全面的分析,运用Banach压缩映射原理和Schauder不动点定理,得到并证明了边值问题解的存在性定理.最后,给出了两个例子来证明结论有效. 相似文献