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991.
用高效毛细管电泳前沿分析法研究了酸性药物那格列奈与人血浆白蛋白的结合常数、结合位点和结合率。使用未涂层的毛细管柱 (4 0cm× 5 0 μmi.d .;有效柱长 32cm) ,磷酸盐缓冲溶液 (pH 7.4 ,离子强度0 .17)为背景溶液 ,在紫外检测波长 2 14nm、运行电压 18kV和重力进样 10 0s的条件下 ,利用那格列奈谱峰的平台高度和游离药物浓度的良好线性关系 (r>0 .999,n =6 ) ,测定了那格列奈的游离药物浓度。固定药物浓度 (2 0 0 μmol L ,2 5 0 μmol L) ,考察不同的蛋白质浓度对结合的影响 ;固定蛋白质浓度 (10 0 μmol L) ,考察不同的药物浓度对结合的影响。实验数据采用非线性拟和程序进行处理 ,得到了那格列奈的蛋白质结合参数。高效毛细管电泳前沿分析法测定的数据重现性良好 (RSD <2 .5 % ,n =3) ,在药代动力学和药效学研究方面具有简便、准确的优点。 相似文献
992.
Bahram Hemmateenejad Hashem Sharghi Morteza Akhond Mojtaba Shamsipur 《Journal of solution chemistry》2003,32(3):215-226
The influence of solvent properties on acidity constants of some newly synthesized 9,10-anthraquinone and 9-anthrone derivatives was studied in methanol-water mixtures in a composition range of 0.57 to 1.0 methanol mole fraction. The model was established by using both multiple linear regression and target factor analysis. Both methods revealed that the solvent polarity/polarizability parameter * is a major factor in controlling the acidity behavior of the anthraquinones and anthrones studied in binary methanol-water mixed solvents. A QSPR study was conducted to drive the relationships between the * coefficient s and the polarity/polarizability of molecules. Both dipole moment and polarizability were found to have a linear relationship with s. The results confirm that, in the dipolar protic solvents used, the dipole-dipole interaction (for neutral molecules) and the ion-dipole interaction (for ionized molecules) are the major factors controlling the acidity behavior of these compounds. 相似文献
993.
Apirat Laobuthee Hatsuo Ishida Suwabun Chirachanchai 《Journal of inclusion phenomena and macrocyclic chemistry》2003,46(3-4):179-185
This study was carried out with the aim to optimize the dissolution propertiesof diclofenac (DIC) – a non-steroidal anti-inflammatory drug sparingly solublein water – through association -with -cyclodextrin (CD). Theeffect of CD on the aqueous solubility of DIC was evaluated by thephase solubility method. The amount of DIC dissolved increased linearly withthe addition of CD according to an AL type plot and without precipitationof the complex. The apparent stability constant of the complex, calculated supposinga 1:1 stoichiometry, was 295 M-1; this value was confirmed by circulardichroism analysis. DIC/CD interactions were also studied in water by1H and 13C NMR spectroscopy. Equimolar DIC/CD solid systems were prepared by physical-mixing, kneading, co-evaporation andfreeze-drying, and their properties in the solid state studied by DifferentialScanning Calorimetry, X-ray powder diffractometry and Fourier-TransformInfrared analysis. For sake of comparison, the mixture of DIC and CDseparately lyophilized was investigated too. The results demonstrated that thefreeze-dried product had the highest degree of amorphization and they were inagreement with the existence of an inclusion complex in the solid state. Thedissolution profiles of the drug from each solid system were affected by its physico-chemical properties, the freeze-dried being the most rapidly dissolvingforms. 相似文献
994.
995.
以壳聚糖(CS)对SiO2进行表面修饰, 采用浸渍还原法制备了负载型Ni-B非晶态合金催化剂(Ni-B/CS/SiO2), 并采用XRD、FTIR、电感耦合等离子体发射光谱(ICP)、BET、XPS、TEM、SAED等表征方法研究了催化剂的非晶性质、原子组成、尺寸分布及粒径大小等. 考察了催化剂对糠醇加氢制四氢糠醇反应的催化性能, 并与没有壳聚糖修饰的Ni-B/SiO2催化剂及Raney Ni催化剂进行了对比. 结果表明, 加入壳聚糖制得的Ni-B/CS/SiO2催化剂的活性组分Ni-B团簇粒径更小, 表面活性组分浓度更高, 催化活性更高. 相似文献
996.
Atsushi Yamazoe 《Tetrahedron letters》2004,45(45):8359-8362
Indole 3-acetic acid, a plant hormone auxin, regulates every aspects of plant growth and development. In the screening for specific inhibitors on auxin signaling using the transgenic Arabidopsis plant harboring the auxin-responsive reporter gene, terfestain A was found to be a novel inhibitor of auxin signaling from the culture of Streptomyces sp. F40. The structure of terfestatin A was determined to be p-terphenyl β-glucoside on the basis of spectroscopic analyses, chemical degradation, and total synthesis. 相似文献
997.
The thermal behaviour of [Ba(C2H6O2)4][Sn(C2H4O2)3] used as a BaSnO3 precursor, and its phase evolution during thermal decomposition are described. The initially formed transient barium tin oxycarbonate phase disintegrates into BaCO3 and SnO2, reacting subsequently to BaSnO3. The existence of the intermediate oxycarbonate phase is evidenced by Fourier transformed infrared (FT-IR), X-ray powder diffraction (XRD) and electron energy loss spectroscopy (EELS (ELNES)) investigations. 相似文献
998.
999.
Thiocarbonylchloride reacts with -nitroalcohols yielding symmetrical thionocarbonates. Transesterification of bis(2-fluoro-2,2-dinitroethyl)thioncarbonate affords alkyl 2-fluoro-2,2-dinitroethylthionocarbonates. Fluorination of these thionocarbonates yields the corresponding difluoroformals.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 375–376, February, 1993. 相似文献
1000.
G. Stringari Ivo Pancheri Frank Möller Osvaldo Failla 《Accreditation and quality assurance》1998,3(3):122-126
Chemical analyses of trace elements are affected by relatively high analytical errors due to the different steps of the laboratory
procedures: samples grinding, mineralisation and instrumental measurements. In the present communication, the influence of
the grinding phase on the global uncertainty of Pb, Cd, Ni and Cr determinations in plant samples by the classical method
of atomic absorption spectrometry/electrothermal atomisation (AAS-ETA) after dry ashing is quantified. Two grinding machines,
a planetary mill with balls and jars of agate versus a stainless steel grinder were compared by analysing leaf samples of
cucumber, strawberry, kiwivines, apple trees and grapevines from agricultural experimental plots under controlled conditions.
Variance components due to the difference between grinding methods and experimental plots were estimated. Further, the simultaneous
effects of the grinding methods on all considered metals have been evaluated by analysis of variance. With the stainless steel
grinder, on average, higher levels of the considered heavy metals were obtained (up to 67% of the mean values). On average,
the increments were similar for metals contained in steel (Ni and Cr) and those not contained (Pb and Cd). The true causes
of these differences need further investigation to determine whether the higher metal detection is due to possible contamination,
to a different grinding quality or to other reasons. Finally, the grinding methods did not seem to affect the combined uncertainty
of the analyses.
Received: 3 November 1997 · Accepted: 29 November 1997 相似文献