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排序方式: 共有233条查询结果,搜索用时 62 毫秒
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2.
Takuji Hirose Kumiko Naito Megumi Nakahara Hiroaki Shitara Yoshio Aoki Hiroyuki Nohira Bruce W. Baldwin 《Journal of inclusion phenomena and macrocyclic chemistry》2002,43(1-2):87-93
Two Kemp's acid diamides were synthesized and applied to chiral amine recognition using 1H NMR analysis. One derivative based on 1-(1-naphthyl)ethylamine had good chiral recognition of six amines and was useful to determine the optical purity for three amines, i.e., methylbenzylamine, 1-(1-naphthyl)ethylamine and 1- henylpropylamine,however, the cyclohexylethylamine derivative showed little discrimination for the amines studied. Together with the results for alkylamines, it was shown that aromatic structure was important for aromatic shielding anisotropy and –– interactions between host and guest. The structure of the 1-(1-naphthyl)ethylamine derivative in solution was also considered based on 1H NMR data and computer simulation. 相似文献
3.
A poly(N-isopropylacrylamide) (PNIPAAm)-like biodegradable thermosensitive polydepsipeptide, poly[Glc-Asn(N-isopropyl)], was synthesized by introducing an isopropyl amide group into poly[Glc-Asn]. Poly[Glc-Asn(N-isopropyl)] was degraded in vitro by cleavage of the ester bonds in the main chain in water at room temperature. The non-toxic nature of the polymer and its degradation products, coupled with a cloud point at 29 degrees C in water, make this polymer attractive for biomedical implant applications. 相似文献
4.
Utilizing a commercially available helium-purging device and PEEK tubes for all tubing, especially for connection between the mobile phase and pump, high performance liquid chromatography with an electrochemical detector (ECD/HPLC) at the cathodic mode is a simple and precise method for the determination of p-nitrophenol (NP). Studies with cyclic and hydrodynamic voltammetry indicated that 25% aqueous MeOH containing 0.1% (v/v) CF(3)CO(2)H and -0.8 V vs. Ag/AgCl are the best mobile phase and detection potential for cathodic ECD/HPLC. With the present system, the limits of detection and determination were 0.2 and 0.25 microM, respectively, and up to 50 microM, a linear calibration curve was afforded. Within-day precisions for the analysis of 5 and 50 microM NP were 0.8 and 0.7% (n=6), respectively, and between-day precisions (n=6) for these samples were 3.5 and 2.2%, respectively. Compared with the commonly used Bessey-Lowry-Brock method, cathodic ECD/HPLC was useful for the assay of acid phosphatase in urine samples with p-nitrophenyl phosphate disodium salt as a substrate. 相似文献
5.
Reaction of 3-methoxy- or 3-chloropyrazine 1-oxides with refluxing phosphoryl chloride in the presence of amine led to a high regioselective formation of 3-substituted 2-chloropyrazines. In contrast, the use of chloroacetyl chloride instead of phosphoryl chloride enabled different regioselectivity to yield 6-substituted 2-chloropyrazines, particularly 3-methoxycarbonylpyrazine 1-oxide was almost exclusively converted into methyl 6-chloropyrazinecarboxylate under the conditions without the amine. 相似文献
6.
Yamamoto Y Yamamoto A Furuta SY Horie M Kodama M Sato W Akiba KY Tsuzuki S Uchimaru T Hashizume D Iwasaki F 《Journal of the American Chemical Society》2005,127(42):14540-14541
The oxidized octaethyltetraphenylporphyrin (1, OETPP) and the corresponding newly prepared octaisobutyltetraphenylporphyrin (3, OisoBuTPP) could be isolated from the reaction of OETPPLi2 (or OisoBuTPPLi2) with SOCl2. The X-ray analysis and the characteristic UV-vis spectra of 1 and 3 revealed that these are the first examples of 16 pi nonaromatic porphyrins. 相似文献
7.
Lim LW Hirose K Tatsumi S Uzu H Mizukami M Takeuchi T 《Journal of chromatography. A》2004,1033(2):205-212
An on-line sample enrichment system was designed using monolithic precolumns in microcolumn LC. The monolithic ODS capillary columns were prepared via in situ sol-gel processes. The enrichment efficiency of the monolithic columns was tested by using phthalates as the analytes. The relative standard deviations (n = 6) for the retention time, peak area and peak height were between 0.4 and 1.2%, 0.9 and 5.5% and 0.4 and 3.9%, respectively. The system was linear (R2 > 0.99) within the working sample concentration and sample volume ranges. Comparing to 0.2 microl injection with a typical sample injector, the theoretical plate number of a same separation column was increased by 3-6-fold when the precolumn unit was used for sample injection. The recoveries of the analytes were between 88 and 120%, and the sample volume that could be injected into the system was increased up to 5000-fold. The limits of detection were improved by more than 2000-fold and were between 0.21 and 0.87 ng ml(-1) even with a UV absorbance detector. This system was applied to the determination of phthalates contained in laboratory distilled water and tap water samples. 相似文献
8.
Evaluation of the adsorption affinity of proteins to calcium hydroxyapatites by desorption and pre-adsorption methods 总被引:1,自引:0,他引:1
Kazuhiko Kandori Aya Fujiwara Megumi Mukai Akemi Yasukawa Tatsuo Ishikawa 《Colloids and surfaces. B, Biointerfaces》1998,11(6):313-320
The adsorption affinity of bovine serum albumin (BSA) and lysozyme (LSZ) to calcium hydroxyapatite (CaHAP) was evaluated by desorption and two step adsorption methods. These experiments were carried out at 15°C in a 1×10−4 mol dm−3 KCl solution of pH 6.0. BSA molecules were scarcely desorbed, exhibiting an irreversible adsorption of BSA, though LSZ slightly desorbed. This result supports our previous findings that LSZ adsorbs weakly onto phosphate ions exposed on ac or bc faces of CaHAP while BSA adsorbs strongly onto positively charged sites on ac or bc faces of CaHAP. The amount of adsorbed LSZ was markedly increased by the pre-adsorption of BSA, where LSZ was adsorbed onto BSA-covered CaHAP. On the other hand, the amount of adsorbed BSA was not changed by the pre-adsorption of LSZ. In both pre-adsorption systems it was confirmed by an HPLC method that no protein molecule pre-adsorbed was desorbed after the post-adsorption procedure. Therefore, it was interpreted that the enhancement of adsorption of positively charged LSZ is induced by an electrostatic attractive force through pre-adsorption of negatively charged BSA molecules with a high coverage. However, since the coverage of LSZ onto CaHAP is considerably low, no stimulation of BSA adsorption occurred on the LSZ-covered surface. The formation of double protein adsorbed layers consisting of pre- and post-adsorbed proteins was proposed. 相似文献
9.
A preparative high-speed counter-current chromatography (HSCCC) method for isolation and purification of coumarin compounds from the Chinese medicinal plant Peucedanum decursivum (Miq.) Maxim (Zihuaqianhu in Chinese) was successfully established by using light petroleum-ethyl acetate-methanol-water (5:5:7:4, v/v) as the two-phase solvent system. The upper phase of light petroleum-ethyl acetate-methanol-water (5:5:7:4, v/v) was used as the stationary phase of HSCCC. Nodakenetin (2.8 mg), 6.1 mg of Pd-C-IV, 7.3 mg of Pd-D-V, 4.7 mg of ostruthin, 7.8 mg of decursidin and 11.2 mg of decursitin C with the purity of 88.3%, 98.0%, 94.2%, 97.1%, 97.8% and 98.4%, respectively, were separated successfully in one-step separation from 150 mg of crude sample from P. decursivum (Miq.) Maxim. After purified by HSCCC again with light petroleum-ethyl acetate-methanol-water (5:5:4:5, v/v) as the two-phase solvent system, the purity of (I) can reach 99.4%. The structures of all the compounds were identified by 1H NMR and 13C NMR. 相似文献
10.
Yano M Taketsugu T Hori K Okamoto H Takenaka S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(16):3991-3999
The series of alkyl 4-[2-(perfluorooctyl)ethoxy]benzoates (F8-n) shows a systematic change of crystal structures depending on the length of the alkyl chain: separate packing of perfluorooctyl (Rf) and alkyl (Rh) chains from each other for shorter (n=2) and longer (n=11) members, alternate packing of Rf and Rh chains for middle (n=6,7) members, and an intermediate type of packing for n=4. Semiempirical MO calculations show slightly repulsive interactions between the Rf chains, and attractive ones between Rf and Rh chains and between Rh and the core of a molecular pair. It is concluded that fluorination determines the molecular shape of the crystal structures by making the chain rigid. It is confirmed that the interactions between Rf chains are small compared with those between other moieties and that they are forced to aggregate owing to the exclusion from other moieties. Thus, the effect is dependent on the geometries and intermolecular interactions of the other moieties. 相似文献