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121.
122.
V. Percec A. D. Asandei Q. Zheng 《Journal of polymer science. Part A, Polymer chemistry》2000,38(19):3631-3655
(S)‐1‐Cyano‐2‐methylpropyl‐4′‐{[4‐(8‐vinyloxyoctyloxy)benzoyl]oxy}biphenyl‐ 4‐carboxylate [ (S)‐11 ] and (R)‐1‐cyano‐2‐methylpropyl‐4′‐{[4‐(8‐vinyloxyoctyloxy)benzoyl]oxy}biphenyl‐4‐carboxylate [( R)‐11 ] enantiomers, both greater than 99% enantiomeric excess, and their corresponding homopolymers, poly[ (S)‐11 ] and poly[ (R)‐11 ], with well‐defined molecular weights and narrow molecular weight distributions were synthesized and characterized. The mesomorphic behaviors of (S)‐11 and poly[ (S)‐11 ] are identical to those of (R)‐11 and poly[ (R)‐11 ], respectively. Both (S)‐11 and (R)‐11 exhibit enantiotropic SA, S, and SX (unidentified smectic) phases. The corresponding homopolymers exhibit SA and S phases. The homopolymers with a degree of polymerization (DP) less than 6 also show a crystalline phase, whereas those with a DP greater than 10 exhibit a second SX phase. Phase diagrams were investigated for four different pairs of enantiomers, (S)‐11 /( R)‐11 , (S)‐11 /poly[ (R)‐11 ], and poly[ (S)‐11 ]/poly[ (R)‐11 ], with similar and dissimilar molecular weights. In all cases, the structural units derived from the enantiomeric components are miscible and, therefore, isomorphic in the SA and S phases over the entire range of enantiomeric composition. Chiral molecular recognition was observed in the SA and SX phases of the monomers but not in the SA phase of the polymers. In addition, a very unusual chiral molecular recognition effect was detected in the S phase of the monomers below their crystallization temperature and in the S phase of the polymers below their glass‐transition temperature. In the S phase of the monomers above the melting temperature and of the polymers above the glass‐transition temperature, nonideal solution behavior was observed. However, in the SA phase the monomer–polymer and polymer–polymer mixtures behave as an ideal solution. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3631–3655, 2000 相似文献
123.
以R(-)-4-N,N-二甲基磺酰胺-7-(3-异氰酸吡咯烷)-2,1,3-苯并氧杂咪唑(R(-)-DBD-PyNCS)为手性荧光衍生化试剂,成功地拆分了甲状腺素对映体D,L-四碘甲状腺原氨酸(T4)和L-三碘甲状腺原氨酸(T3)。在反应温度为40 ℃、反应时间为20 min时,R(-)-DBD-PyNCS在碱性介质中可与甲状腺素对映体生成稳定的非对映体衍生物。该衍生物在以乙腈-水-醋酸(体积比为60∶40∶1)为流动相,流速为1.0 mL/min,色谱柱为Intersil-ODS-3 C18柱(150 mm×4.6 mm,5 μm)的色谱条件下得到了充分的分离。采用荧光检测器在激发波长460 nm、发射波长550 nm下检测。D,L-T4和L-T3分别在0.016~0.30 μg/μL和0.0067~0.22 μg/μL范围内,峰面积与浓度呈良好的线性关系(r>0.999)。D,L-T4和L-T3的最低检出限分别为0.02 μg/mL和0.85 μg/mL(S/N=3)。在D-T4、L-T4、L-T3质量浓度分别为0.10 μg/μL下测得峰面积的相对标准偏差分别为3.40%,1.63%,3.30%(n=7)。该方法成功地应用于甲状腺片中T4和T3的含量测定。 相似文献
124.
The use of cyclodextrin derivatives for the efficient separation of enantiomeric drugs is described. Hydroxypropylation, methylation or carboxymethylation of the cyclodextrin not only result in a better solubility of the cyclodextrin in aqueous solutions, but also favor, via additional hydrogen bonding, the stabilization of one of the cyclodextrin-analyte complexes. The influence of the background electrolyte on peak shape is also described here. Carboxymethylated cyclodextrin can be used in similar manner to uncharged cyclodextrins at low pH values (below 4). At pH values above 5, however, its charge also allows the separation of uncharged enantiomers as in a micellar-like system. 相似文献
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127.
首次以具有适当疏水性的甲状腺素衍生物O-methyl-T4为半抗原,用杂交瘤技术得到相应的抗体(6E8),又经过苯甲基磺酰氟和NaHSe的化学修饰引入了催化基团硒代半胱氨酸,制备出具有较高甲状腺素脱碘酶活力的抗体酶(Se-6E8).用SDS-PAGE电泳对Se-6E8的纯度进行了鉴定,同时研究了其解离常数、温度及pH等酶学性质.结果表明,Se-6E8活力为2010U/μmolprotein,纯度达到电泳纯,催化反应的最适温度为57℃,最适pH为82. 相似文献
128.
129.
C. Álvarez J. A. Sánchez-Brunete S. Torrado-Santiago R. Cadórniga J. J. Torrado 《Chromatographia》2000,52(7-8):455-458
Summary An easy and rapid enantioselective separation for assay of racemic thalidomide on an immobilized α1-acid glycoprotein chiral stationary phase (GPA CSP) is described. The effects of tetrahydrofuran (THF) as organic modifier,
buffer concentration to control the ionic strenth, and mobile phase pH were studied. These variations have consequences in
terms of chromatographic retention (k), resolution (R
s), selectivity (α), and peak asymmetry (USP tailing factor). The main condition affecting chromatographic retention was mobile
phase pH. At pH 4.5, no separation of thalidomide enantiomers was achieved whereas at pH 7.9 chiral separation was optimum.
Peak tailing was directly related to changes in pH and to addition of THF as mobile phase modifier. Results also indicated
that the resolution factor is THF concentration-dependent, and that the separation factor (α) is the best parameter for evaluating
enantioselectivity. The best mobile phase was pH 7.0, 30 mM ammonium acetate containing 0.3% THF. Under these conditions validation
including linearity, recovery, and precision was performed. The suitability of this method has been successfully proved in
a limited in-vivo study after intravenous administration of thalidomide to a New Zealand male rabbit. 相似文献
130.
Qianqian Jia Jia Fu Peida Liang Saisai Wang Yamin Wang Xin Zhang Huaxin Zhou Liyang Zhang Yanni Lv Shengli Han 《Journal of separation science》2022,45(2):456-467
Chloroquine and hydroxychloroquine have been studied since the early clinical treatment of SARS-CoV-2 outbreak. Considering these two chiral drugs are currently in use as the racemate, high-expression angiotensin-converting enzyme 2 cell membrane chromatography was established for investigating the differences of two paired enantiomers binding to angiotensin-converting enzyme 2 receptor. Molecular docking assay and detection of SARS-CoV-2 spike pseudotyped virus entry into angiotensin-converting enzyme 2-HEK293T cells were also conducted for further investigation. Results showed that each single enantiomer could bind well to angiotensin-converting enzyme 2, but there were differences between the paired enantiomers and corresponding racemate in frontal analysis. R-Chloroquine showed better angiotensin-converting enzyme 2 receptor binding ability compared to S-chloroquine/chloroquine (racemate). S-Hydroxychloroquine showed better angiotensin-converting enzyme 2 receptor binding ability than R-hydroxychloroquine/hydroxychloroquine. Moreover, each single enantiomer was proved effective compared with the control group; compared with S-chloroquine or the racemate, R-chloroquine showed better inhibitory effects at the same concentration. As for hydroxychloroquine, R-hydroxychloroquine showed better inhibitory effects than S-hydroxychloroquine, but it slightly worse than the racemate. In conclusion, R-chloroquine showed better angiotensin-converting enzyme 2 receptor binding ability and inhibitory effects compared to S-chloroquine/chloroquine (racemate). S-Hydroxychloroquine showed better angiotensin-converting enzyme 2 receptor binding ability than R-hydroxychloroquine/hydroxychloroquine (racemate), while the effect of preventing SARS-CoV-2 pseudovirus from entering cells was weaker than R-hydroxychloroquine/hydroxychloroquine (racemate). 相似文献