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911.
In this study, we developed an analytical method for the enantioseparation of ofloxacin, using capillary electrophoresis with fluorescence detection. The optimum background electrolyte was obtained to be 60 mM hydroxylpropyl‐β‐cyclodextrin (HP‐β‐CD) in 50 mM phosphate buffer at pH 2.30. Under these conditions, the (+) and (‐) ofloxacin were completely separated, with the detection limit of 10 nM when the sample was prepared in deionized water. The linear ranges of levofloxacin in deionized water and untreated urine were 10?7 to 5 × 10?3 M with R2 = 0.9989 and 5 × 10?6to 5 × 10?3 M with R2 = 0.9943, respectively. We also applied this method to investigate the purity of a commercial drug. The results revealed that the ratio between (+)‐ofloxacin and (‐)‐ofloxacin (levofloxacin) was 99.9:0.1, and there is about 93 mg levofloxacin per tablet (200 mg). The concentration of levofloxacin in patient's urine was founded to be 7.9 × 10?4M, and the ratio between the two optical isomers was 99.3:0.7. 相似文献
912.
Jean‐Louis Schmitt Adrian‐Mihail Stadler Nathalie Kyritsakas Jean‐Marie Lehn 《Helvetica chimica acta》2003,86(5):1598-1624
Control over the folding of molecular strands may be achieved by appropriate choice of the constituting subunits, in particular for chains of specific heterocycles such as sequences of directly connected pyridine (py) and pyrimidine (pym) rings, which are known to fold into extended helical structures. Since the hydrazone (hyz) group represents an isomorphic analogue of a py site, the condensation of hydrazine and carboxaldehyde derivatives of pym offers a very efficient approach to strands incorporating hyz instead of py units and constituted by sequences of alternating hyz and pym groups. A series of such strands of different lengths, up to ten hyz units, i.e., 1 – 7 , were synthesized. Their spectral properties indicate that they fold indeed into helical shapes. Extensive characterization was performed in solution by 1HNMR spectroscopy and in the solid state by determination of the crystal structures of eight such strands. They all display the expected helical geometry with up to 3 1/3 turns and direct stacking contacts. The efficiency and flexibility of the synthetic approach as well as its wide potential for generation of diversity through lateral decoration make the (hyz? pym) subunit a particularly attractive helicity codon. 相似文献
913.
Qing‐Xiang Liu Feng‐Bo Xu Qing‐Shan Li Xian‐Shun Zeng Xue‐Bing Leng Zheng‐Zhi Zhang 《中国化学》2002,20(9):878-883
Dinuclear silver (I) six‐membered ring complex [Ag2 (bta)2 ‐(hmbta)2] (ClO4)2 (3) has been synthesized by the reaction of benzotriazole (bta) (1) and 1‐hydroxymethyl benzotriazole (hmbta) (2) with Ag (CH3CN)4ClO4. The structures of compound 2 and Complex 3 have been studied by single crystal X‐ray diffraction analysis. The change of luminescent intensity of 1, 2 and 3 was reported. Compound 2 crystallizes in the monoclinic system with space group P2 (1)/c, a = 0.7655 (10) nm, b = 1.0126 (14) nm, c =0.9502 (13) nm, β = 95.07 (2)°, V = 0.7337 (17) nm3 and Z = 4. Complex 3 crystallizes in the triclinic system with space group P1, a = 0.73611 (18) nm, b = 0.9152 (2) nm, c = 1.2277 (3) nm, β = 87.170 (5)°, V = 0.8221 (3) nm3 and Z = 1. The main structural feature of complex 3 is a symmetric dinuclear six‐membered ring formed by two silver (I) atoms and four N‐atoms from two benzotriazoles. The second structural feature of complex 3 is the τ‐τ stacking interaction between two adjacent molecular planes, which forms the two‐dimentional layer structure. Besides, compared with 2, the luminescent intensity of complex 3 shows a remarkable enhancement. 相似文献
914.
Electrochemistry and Raman spectroscopy have shown that aquocob(III)alamin (Cbl(III)) can be reduced by nitric oxide (NO) to form Cbl(II) on an electrode surface. The Cbl(II) formed in this way can bind NO to form nitrosyl-cobalamin, Cbl(II)-NO, which is reduced to form Cbl(I) at about -1.0 V vs a KCl saturated Ag/AgCl reference electrode. In addition, nitrite was found to bind both Cbl(III) and Cbl(II) and a binding constant of 3.5 x 10(2) M(-1) was measured for (NO(2)-Cbl(II))(1-). UV-vis spectrophotometry and mass spectroscopy were used to show that Cbl(I) reduces NO to form Cbl(II)-NO and N(2)O and N(2), and this reaction is involved in the cyclic voltammetry of cobalamin in the presence of excess NO where a catalytic reduction of NO occurs involving the cycling of Cbl(II)-NO/Cbl(I). This redox couple is also involved in the electrochemical catalytic reduction of nitrite. These results can be used to explain a number of physiological effects involving NO interaction in biological systems with added cobalamin or with cobalamin in the methionine synthase enzyme. 相似文献
915.
A protein array for cell detection was fabricated by spotting different antibodies on modified glass slides. Glass slides were modified to allow antibodies to be immobilized on it and to selectively bind antigens. Antibodies were specially selected with the cells to be detected as targets, which permitted target cells in samples to bind specifically to the array with little nonspecific binding. Results can be obtained by directly putting the samples onto the array for 1 h or a little longer to let the cells specifically interact with the antibodies. After washing the unbound samples away, images were observed with a microscope and captured with a CCD camera. The assessment of antibody-cell binding was evaluated by capturing red blood cells (RBCs) in human blood with blood group antibodies (anti-A and anti-B). Blood group antibodies were spotted on the modified glass slide and kept at 4<.deg> degrees C overnight for immobilization. Human blood samples diluted to different concentrations were used to examine the sensitivity and specificity of the method. 相似文献
916.
An oligosaccharide homologue named SnS-2 was isolated from the root of Scrophularia ningpoensis Hemsl.SnS-2 was purified by means of gel-permeation chromatography and ion-exchange chromatography. Its physicochemical properties, including carbohydrate content and molecular weight were determined. The structure of SnS-2 was elucidated by chemical methods along with ^1H and ^13C NMR spectroscopy, including two-dimensional DQCOSY and H-detected ^1H, ^13C HMQC experiments. These results show that SnS-2 possesses a backbone consisting of terminal α-Galp-(1→, α-Galp-(1→6), α-Glcp-(1→6) and nonreducing end β-Fruf-(2→. The bioactive assay showed that it could inhibit the growth of Lewis pulmonary carcinoma implanted in mice. 相似文献
918.
919.
920.
三核铁甲酸配合物的热解过程及其若干催化活性碎片的研究 总被引:1,自引:0,他引:1
三重桥氧三核铁甲酸配合物[Fe_3(μ_3-O)(μ-O_2CH)_6(H_2O)_2·(O_2CH)]·2H_2O的热反应行为十分有趣,其在热解过程某阶段失去部分配体后的碎片能活化乙炔进行加氢或加水反应生成乙烯、乙醛和丙酮,为揭示这些活性碎片的本质,我们应用了原位红外光谱(in situ IR),热重(TG)、差热分析(DTA),气相色谱(GC)、X-射线粉未衍射(XRD)和质谱(MS)等手段综合研究该化合物的热解过程,求出各热解碎片的组成,并研究它们在不同条件下的反应性能.本文报道它们相互验证的定性及定量结果. 相似文献