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91.
Nicotine is the primary psychoactive component in tobacco. It is taken into the body by tobacco smoking, and mainly metabolized to cotinine in the hepatic cytochrme P450 (CYP) 2A6. The objective of this study was to develop a sensitive method for the determination of nicotine metabolism to cotinine using HPLC. The internal standard, trans-4'-carboxycotinine methyl ester was synthesized with a simple method. The nicotine and cotinine were separated completely and detected by C(18) 5-μm analytical column (L-column Octa decyl silyl (ODS), 150 mm × 4.6 mm i.d.) equipped with a C(18) 5-μm guard column (L-column ODS, 10 mm × 4.6 mm i.d.) and ultraviolet detection at 260 nm. The detection limit of the assay was 0.05 μM for cotinine (n=5, R.S.D) and 0.1 μM for nicotine. Thus the present results provided a sensitive and useful method for the determination of nicotine metabolism catalyzed by CYP2A6. 相似文献
92.
Takigawa A Setoguchi H Okawa M Kinjo J Miyashita H Yokomizo K Yoshimitsu H Nohara T Ono M 《Chemical & pharmaceutical bulletin》2011,59(9):1163-1168
Alkaline hydrolysis of the crude resin glycoside fraction of the leaves, stems, and roots of Calystegia soldanella ROEM. et SCHULT. (Convolvulaceae) gave four new glycosidic acids, named calysolic acids A, B, C, and D, along with one known glycosidic acid, soldanellic acid B, and three organic acids, 2S-methylbutyric, tiglic, and 2S,3S-nilic acids. The structures of the new glycosidic acids were characterized on the basis of spectroscopic data and chemical evidence. 相似文献
93.
Tomoko Mineno Rie Tsukagoshi Tsubasa Iijima Kazuki Watanabe Hiroyuki Miyashita Hitoshi Yoshimitsu 《Tetrahedron letters》2014
A reductive coupling reaction was effectively developed to convert an aldehyde to its symmetrical ether. The successful reactions required Et3SiH and CH2Cl2 as the suitable solvent in the presence of a catalytic amount of In(OTf)3. Various aldehydes were subjected to the method, and each afforded the expected ethers in good to excellent yields. 相似文献
94.
Tomoaki Nishimura Yoshito Sasaki Yoshimitsu Tachi Shuichi Suzuki Keiji Okada Masatoshi Kozaki 《化学:亚洲杂志》2020,15(5):594-600
A stimulus‐responsive receptor 1 was designed and prepared to control the ligand‐binding ability of three active sites, two zinc tetraphenylporphyrin units (P1) and one zinc diethynyldiphenylporphyrin unit (P2), with one effector molecule 2 . Bulky hexarylbenzene units were incorporated as shielding panels in the middle of the flexible side arms of 1 . Spectroscopic titrations indicated that a stable supramolecular complex 1 ? 2 (K 1 ? 2 =6.7×106 m ?1) was produced by the cooperative formation of multiple hydrogen and coordination bonds. As a result, the binding of a ligand to P1 was inhibited by 2 in a competitive manner. Additionally, the formation of 1 ? 2 brought about conformational restriction of the side arms to cover both faces of P2 with the shielding panels. The binding constant of 4‐phenylpyridine with P2 in 1 ? 2 decreased to 8.9 % of that in 1 . Namely, the ligand‐binding ability of P2 was inhibited according to an allosteric mechanism. 相似文献
95.
The modification of the InAs quantum dots (QDs) by the GaAs capping growth was studied by using cross-sectional STEM and atomic force microscopy. In case of the GaAs capping growth at 450 °C, it was found that the lateral size of the InAs QDs significantly decreases rather than the height and that this size-shrinkage effect is enhanced for the large QDs. The shrinkage behavior is mainly attributed to the indium surface segregation, strongly depending on the surface strain of the QDs. The growth process of the GaAs capping layer plays an important role for achieving the size ordering of the embedded QDs. 相似文献
96.
Hirokazu Tanaka Yoshikuni Itoh Hiroichi Ikushima Masanori Okamoto Yoshio Kawai Hiroshi Imanaka 《Tetrahedron letters》1980,21(45):4359-4360
The structure elucidation and synthesis of WS 5995, produced by , were described. 相似文献
97.
Luminescence of high density electron-hole plasma in CdSe is observed in the 77–300 K temperature range by picosecond pulse excitation. With increasing temperature from 77 K the stimulated emission band is replaced by the spontaneous emission band. Temperature changes of spectral features of these two bands and also their time dependence after pulse excitation are consistent with the theoretical consideration. 相似文献
98.
Redesigning enzymes based on adaptive evolution for optimal function in synthetic metabolic pathways 总被引:1,自引:0,他引:1
Nature has balanced most metabolic pathways such that no one enzyme in the pathway controls the flux through that pathway. However, unnatural or nonnative, constructed metabolic pathways may have limited product flux due to unfavorable in vivo properties of one or more enzymes in the pathway. One such example is the mevalonate-based isoprenoid biosynthetic pathway that we previously reconstructed in Escherichia coli. We have used a probable mechanism of adaptive evolution to engineer the in vivo properties of two enzymes (3-hydroxy-3-methylglutaryl-CoA reductase [tHMGR] and many terpene synthases) in this pathway and thereby eliminate or minimize the bottleneck created by these inefficient or nonfunctional enzymes. Here, we demonstrate how we significantly improved the productivity (by approximately 1000 fold) of this reconstructed biosynthetic pathway using this strategy. We anticipate that this strategy will find broad applicability in the functional construction (or reconstruction) of biological pathways in heterologous hosts. 相似文献
99.
Treatment of an (o-alkynylphenyl)phosphine with a stoichiometric amount of BuLi effects a cyclization reaction to produce a 3-lithiobenzo[b]phosphole, which affords a variety of 3-substituted benzophospholes upon reaction with electrophiles. An example is given for the synthesis of a bis-benzo[b]phosphole, which can be further converted to the corresponding benzo[b]phosphole oxide possessing high electron affinity. 相似文献
100.
Yuta Fujisawa Dr. Yiling Nan Prof. Dr. Atsushi Asano Dr. Yu Yanagisawa Dr. Keiichi Yano Dr. Yoshimitsu Itoh Prof. Dr. Takuzo Aida 《Angewandte Chemie (International ed. in English)》2023,62(5):e202214444
Can commodity polymers are made to be healable just by blending with self-healable polymers? Here we report the first study on the fundamental aspect of this practically challenging issue. Poly(ether thiourea) (PTUEG3; Tg=27 °C) reported in 2018 is extraordinary in that it is mechanically robust but can self-heal even at 12 °C. In contrast, poly(octamethylene thiourea) (PTUC8; Tg=50 °C), an analogue of PTUEG3, cannot heal below 92 °C. We found that their polymer blend self-healed in a temperature range above 32 °C even when its PTUEG3 content was only 20 mol %. Unlike PTUEG3 alone, this polymer blend, upon exposure to high humidity, barely plasticized, keeping its excellent mechanical properties due to the non-hygroscopic nature of the PTUC8 component. CP/MAS 13C NMR analysis revealed that the polymer blend was nanophase-separated, which possibly accounts for why such a small amount of PTUEG3 provided the polymer blend with humidity-tolerant self-healable properties. 相似文献