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991.
Ding L Liu W Wang W Glinka CJ Worcester DL Yang L Huang HW 《Langmuir : the ACS journal of surfaces and colloids》2004,20(21):9262-9269
A neutron diffraction method applicable to nonlamellar phases of substrate-supported lipid membranes is described and validated. When prepared on a flat substrate, the resulting nonlamellar phases have layered symmetry which provides some advantages over powder diffraction for detailed structure determination. This approach recently led to the detection of a rhombohedral phase and a distorted hexagonal phase of lipids. Here the determination of intensity and phase information for such phases is demonstrated by application to the hexagonal phase of diphytanoyl phosphatidylcholine (DPhPC). The hexagonal symmetry is used to verify the data reduction procedure for the intensities of the diffraction peaks. Diffraction intensities measured while varying the D2O/H2O ratio in the relative humidity was used to solve the phase problem. The neutron scattering length density distribution of the hexagonal phase was constructed and analyzed to elucidate the packing of the lipid molecules. The structure of DPhPC in the hexagonal phase is of interest in connection with its stalk structure in the rhombohedral phase. We also found that the incorporation of tetradecane into the DPhPC hexagonal phase is limited, similar to the case for dioleoyl phosphatidylethanolamine. 相似文献
992.
Huang HS Chiou JF Chiu HF Hwang JM Lin PY Tao CW Yeh PF Jeng WR 《Chemical & pharmaceutical bulletin》2002,50(11):1491-1494
The synthesis of a series of anthraquinone moieties bearing symmetrical sulfur-linked substituents in the 1 and 5 positions is described. These compounds were evaluated for their ability to inhibit the growth of suspended rat glioma C6 cells and human hepatoma G2 cells, respectively. In addition, the redox property of the compounds was determined based on the inhibition of lipid peroxidation in model membranes. Compounds 2a and 2h in this series compared favorably and exhibited the most potent cytotoxicity (0.02, 0.05 microM) against C6 cells in the XTT colorimetric assay. As far as redox properties are concerned, all bis-thio-anthraquinones show potential lipid peroxidation in model membranes very close to that of mitoxantrone (MX), and 2a, 2d, 2e, 2i, 2j, and 2k have more potential than that of MX. The lack of cytotoxicity of compound 2i cannot be related to lipid peroxidation, but the steric and electronic properties of the side-chain substituent maybe impair effective recognition of the cleavable complex. In contrast to MX, 2a and 2h are cytotoxic in rat glioma C6 cells and do not enhance lipid peroxidation in model membranes. 相似文献
993.
Shengqiang Fang Lian Fu Changang Pang 《Journal of Radioanalytical and Nuclear Chemistry》1996,203(1):143-149
The methods including collection method, extraction-collection method, and special extraction-collection method have been investigated for high speed and efficient recovery of palladium from high pH reprocessing waste of spent nuclear fuel. The equilibrium of the reactions can be obtained is less than 1 minute. The maximum percent recovery of Pd is about 89%, 96% and 97% for collection, extraction-collection, and special extraction-collection methods, respectively. Nearly 100% of back extraction of Pd in the organic phase can be attained by using 7.4M ammonia solution, with a phase ratio of 1:1. The purity of the Pd product is high. The percent recovery of Pd is constant, up to 5·103 Gy of irradiation dose. 相似文献
994.
Starting with 1,1-dimethoxy-2-propanone ( 1 ), 6-formyl-1,2-dihydro-2-oxo-3-pyridinecarboxylic acid ( 5a ) has been prepared in large quantities by a highly efficient, 4-step synthesis. This compound, along with its one carbon homologue, 6-acetyl-1,2-dihydro-2-oxo-3-pyridinecarboxylic acid ( 5b ) has been reacted with several carbonyl derivative forming reagents to provide a series of side chains for β-lactams. Among these carbonyl derivatives are styrylamides which were prepared from Wittig and Horner-Emmons reagents. The preparation of the phosphonium salts and phosphonate esters is also described. 相似文献
995.
生色冠醚研究.Ⅱ.2、6-二溴靛酚冠醚在甲醇溶液中与碱金属和碱土金属盐的变色作用 总被引:1,自引:0,他引:1
冠醚化酚(1a,1b)和酚型开链冠醚(2a,2b)在甲醇中氢氧化锂的作用下,与2、6—二溴醌氯亚胺反应,生成兰色的2、6—二溴靛酚冠醚(1c,1d,2c,2d)锂盐。在其甲醇溶液中加入其它碱金属和碱土金属盐时,产生颜色变化,其中以2c和2d表现出对Sr~(2+)和Ba~(2+)有较明显的选择性变色作用,其△λ_(max)(nm)分别为:2c:38(SrCl_2),37(BaCl_2);2d:64(SrCl_2),56(BaCl_2)。还考查了介质中含水量对变色作用的影响和锶盐的阴离子效应,探讨了选择性变色作用的机理。 相似文献
996.
可见光化的半导体光催化剂 总被引:1,自引:0,他引:1
光解水制氢能否实用化取决于太阳光的有效利用率, 研究开发可见光化的光催化剂成为当前光催化剂研究中的重要课题.本文介绍了利用 光解水制氢的反应机理,综述了近年来半导体光催化剂在利用可见光方面的研究进展,重点描述了这些光催化剂的结构,并对该领域今后的研究方向进行了展望. 相似文献
997.
998.
999.
The copper-tellurolate cluster [(Cu(6)(TePh)(6)(PPh(2)Et)(5)] has been loaded into the pores of MCM-41 by solid-state impregnation techniques. It was found that the best loading conditions are 110 degrees C and 10(-)(3) Torr static vacuum. The resulting material was analyzed by powder X-ray diffraction (PXRD), nitrogen adsorption isotherms, thermogravimetric analysis (TGA), (31)P CP MAS NMR spectroscopy, and TEM. It was observed that loading is accompanied by loss of the phosphine shell, with retention of the copper-tellurium core. Condensation of the impregnated material may proceed thermally or photochemically. Thermal condensation results in the formation of Cu(2)Te nanoparticles as demonstrated by PXRD, and TEM data suggests that the process has taken place inside the pores of MCM-41. Photochemical condensation yields larger metal-chalcogen clusters in the pores as suggested by the result of UV-vis diffuse reflectance spectroscopy and TEM measurements. 相似文献
1000.
Cui Ping YU Li Fang ZHANG Zhi Quan SHEN Institute of Polymer Science Zhejiang University Hangzhou 《中国化学快报》2003,(10)
The ring-opening polymerization of e-caprolactone (CL) initiated by novel single lanthanide tris(4-tert-butylphenolate)s [Ln(OTBP)3] is reported. Single-component La(OTBP)3 can effectively prepare polycaprolactone (PCL) with over 90% yield and viscosity average molecular weight about 60 x 10 under quite mild conditions: molar ratio of CL to initiator is 1000, 60 C, 2 h in toluene. Mechanism study indicates that the monomer inserts into the growing chain via the break of acyl-oxygen bond of CL. 相似文献