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排序方式: 共有1698条查询结果,搜索用时 15 毫秒
111.
Jang HS Ryu KE Ahn WS Chun HJ Dal Park H Park KD Kim YH 《Colloids and surfaces. B, Biointerfaces》2006,50(2):141-146
Previously, novel poly(ethylene glycol) (PEG) and sulfonated PEG acrylate (PEG-SO3A/OA) copolymers were prepared as coating and/or blending materials for biomedical applications. Surfaces modified with copolymers exhibited increased anti-coagulation properties and decreased plasma adsorption level due to increased hydrophilic properties and reorientation characteristics of PEG/PEG-SO3A chains in water phase. As continuation study, anti-complement effects of PEG-SO3/OA copolymers were investigated in vitro, and compared with those of low-density polyethylene (LDPE) and PEG/OA. C3 activation by PEG-SO3/OA samples was lower than that by PEG/OA samples, which was attributed to decreased surface nucleophile level of samples. PEG-SO3/OA samples increased inhibition of Bb production, resulting in decreased C5 activation. Owing to reduced activations of C3 and C5, PEG-SO3/OA samples markedly decreased SC5b-9 levels in plasma. 相似文献
112.
The effect of metal substitution in La2C2Br2 by Lu (non-magnetic) and Ce (magnetic), respectively, on Tc was studied. The Lu substitution affects Tc, which decreases moderately with increasing amount of Lu. However Ce substitution affects Tc drastically, such that only 10% Ce substitution makes superconductivity disappear. 相似文献
113.
Rho HS Ghimeray AK Yoo DS Ahn SM Kwon SS Lee KH Cho DH Cho JY 《Molecules (Basel, Switzerland)》2011,16(4):3338-3344
The objective of this study was to examine the biological activity of kaempferol and its rhamnosides. We isolated kaempferol (1), a-rhamnoisorobin (2), afzelin (3), and kaempferitrin (4) as pure compounds by far-infrared (FIR) irradiation of kenaf (Hibiscus cannabinus L.) leaves. The depigmenting and anti-inflammatory activity of the compounds was evaluated by analyzing their structure-activity relationships. The order of the inhibitory activity with regard to depigmentation and nitric oxide (NO) production was kaempferol (1) > a-rhamnoisorobin (2) > afzelin (3) > kaempferitrin (4). However, a-rhamnoisorobin (2) was more potent than kaempferol (1) in NF-kB-mediated luciferase assays. From these results, we conclude that the 3-hydroxyl group of kaempferol is an important pharmacophore and that additional rhamnose moieties affect the biological activity negatively. 相似文献
114.
Peterca M Imam MR Ahn CH Balagurusamy VS Wilson DA Rosen BM Percec V 《Journal of the American Chemical Society》2011,133(7):2311-2328
The synthesis, structural, and retrostructural analysis of two libraries containing 16 first and second generation C(3)-symmetric self-assembling dendrimers based on dendrons connected at their apex via trisesters and trisamides of 1,3,5-benzenetricarboxylic acid is reported. A combination of X-ray diffraction and CD/UV analysis methods demonstrated that their C(3)-symmetry modulates different degrees of packing on the periphery of supramolecular structures that are responsible for the formation of chiral helical supramolecular columns and spheres self-organizable in a diversity of three-dimensional (3D) columnar, tetragonal, and cubic lattices. Two of these periodic arrays, a 3D columnar hexagonal superlattice and a 3D columnar simple orthorhombic chiral lattice with P222(1) symmetry, are unprecedented for supramolecular dendrimers. A thermal-reversible inversion of chirality was discovered in helical supramolecular columns. This inversion is induced, on heating, by the change in symmetry from a 3D columnar simple orthorhombic chiral lattice to a 3D columnar hexagonal array and, on cooling, by the change in symmetry from a 2D hexagonal to a 2D centered rectangular lattice, both exhibiting intracolumnar order. A first-order transition from coupled columns with long helical pitch, to weakly or uncorrelated columns with short helical pitch that generates a molecular rotator, was also discovered. The torsion angles of the molecular rotator are proportional to the change in temperature, and this effect is amplified in the case of the C(3)-symmetric trisamide supramolecular dendrimers forming H-bonds along their column. The structural changes reported here can be used to design complex functions based on helical supramolecular dendrimers with different degree of packing on their periphery. 相似文献
115.
Abstract The rate of sulfonation of bead copolymers of styrene cross-linked with 8 mole % divinylbenzene (mixed isomers) is remarkably sensitive to the isomeric (para/meta) composition of the mixture of divinylbenzenes. The rate is enhanced by a factor of 4 for compositions containing 20–40% para isomer. 相似文献
116.
Liu Q Hong IP Ahn MJ Yoo HS Han SB Hwang BY Lee MK 《Natural product communications》2011,6(12):1839-1841
Inhibition of adipocytes differentiation is suggested to be an important strategy for prevention and/or treatment of obesity. In our present study, Cordyceps militaris showed significant inhibitory activity on adipocyte differentiation in 3T3-L1 preadipocytes as assessed by measuring fat accumulation using Oil Red O staining. Activity-guided fractionation led to the isolation of cordycepin (1), guanosine (2) and tryptophan (3) as active compounds. All the three compounds were more effective in the prevention of early stage of adipogenesis than in lipolysis. In addition, combinational treatment of three compounds significantly increased anti-adipogenic activity. 相似文献
117.
118.
Sang-Woo Bae Kihun Ahn Yoon-Mo Koo Sung Ho Ha 《Applied biochemistry and biotechnology》2013,171(5):1289-1298
Ionic liquids (ILs) are molten salts which do not crystallize at room temperature. Tunable physicochemical properties of ILs including hydrophobicity and polarity facilitate their applications in many biological processes. In this study, a copper-based IL was employed in order to enhance the refolding efficiency of laccase from Trametes versicolor which requires copper as a cofactor. When 1-ethyl-3-methylimidazolium trichlorocuprate ([EMIM][CuCl3]) was added to refolding buffer instead of urea, the laccase refolding yield was improved more than 2.7 times compared to the conventional refolding buffer which contains urea. When the refolding of laccase was carried out at different temperatures (4, 25, and 37 °C), the highest refolding yield was obtained at 25 °C. At low temperature, two conflicting effects, i.e., suppression of the aggregate formation and decrease of folding rate, influence the protein refolding. In contrast, a copper-based IL did not enhance the refolding of lysozyme, a non-copper-containing protein. From these results, we can conclude that this copper-based IL, [EMIM][CuCl3], was exclusively effective on the refolding process of a copper-containing protein. 相似文献
119.
Zaesung No Shi Yong Ryu Seong-Kie Kim Jong Woong Ahn Bok Ju Song Keun Jae Kim 《合成通讯》2013,43(5):887-892
Thermal or base-promoted conversion of 5′-O-TBDMS-3′-O-(1H-imidazole-1-thiocarbonyl)thymidine (1) afforded 5′-O-TBDMS-2,3′-anhydro-thymidine (2), a pivotal intermediate for the transformation of the 3′-hydroxy group of 2′-deoxyribonucleosides, in high yield. 相似文献
120.
The palladium-catalyzed arylation and vinylation of 2,3-dihydrofuran with aryl and alkenyl iodonium salts afforded 2-phenyl- or 2-alkenyl-2,5-dihydrofurans at room temperature in an aqueous medium. 相似文献