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261.
Tay-Yean Lin Charles A. Kingsbury Jules Adelfang Norman H. Cromwell 《Journal of heterocyclic chemistry》1985,22(4):1017-1020
The synthesis and spectral characteristics of certain bis(1-alkyl-3-phenyl-2-aziridinyl)ketones are reported. The reactions of 1,2,4,5-tetrabromo-1,5-diphenyl-3-pentanone ( 2 ) with primary amines are assumed to have a mechanism similar to that of a simple dibromo-ketone. The so-called cis, cis- or trans, trans-configurations of the bis-aziridinylketones were determined by 1H and 13C nmr spectra. 相似文献
262.
Mangiferin (2-beta-D-glucopyranosyl-1,3,6,7-tetrahydroxyxanthen-9-one) has been isolated from the herbal root of Anemarrhena asphodeloides Bung showing antioxidative, antiviral, and anticancer effect. An in vivo microdialysis sampling method coupled to microbore high-performance liquid chromatography (HPLC) was employed for continuous monitoring of free mangiferin in rat blood. Microdialysis probes were inserted into the jugular vein/right atrium and brain striatum of Sprague-Dawley rats, and mangiferin at doses of 10, 30 or 100 mg/kg were then administered via the femoral vein. Dialysates were collected every 10 min and injected directly into a microbore HPLC system. Mangiferin was separated by a reversed-phase C18 microbore column (150 x 1 mm) from dialysate within 10 min. The mobile phase consisted of acetonitrile-0.05% phosphoric acid-tetrahydrofuran (10:75:15, v/v/v) with a flow-rate of 0.05 ml/min. The wavelength of the UV detector was set at 257 nm. The limit of quantification for mangiferin was 0.05 microg/ml and in vivo recovery of mangiferin at concentrations of 1, 5 and 10 microg/ml was in range of 37.7-39.8%. The results indicate that the pharmacokinetics of mangiferin at doses of 10-30 mg/kg reveals a linear relation, while doses of 30-100 mg/kg show a nonlinear pharmacokinetic phenomenon. Mangiferin was undetectable in brain dialysate. The proposed method provides a technique for rapid and sensitive analysis of free mangiferin in rat blood and further application in pharmacokinetic study. Furthermore, the metabolites of mangiferin in the rat bile were confirmed by LC electrospray ionization (ESI) tandem mass spectrometry (MS-MS). 相似文献
263.
Lin Z 《Chemical Society reviews》2002,31(4):239-245
Transition metal-silane complexes containing metal-eta 2-H-Si coordination display different structural and bonding characteristics in comparison to other sigma-complexes, such as dihydrogen and alkane (agostic) complexes. The different characteristics can be related to the strong sigma*-accepting properties of the eta 2-silane ligand(s) because of the weaker H-Si sigma bond. Various examples of metal-silane complexes have been reviewed and their structural stabilities have been systematically discussed. Silyl-hydride complexes having substantial silyl-hydrido interactions have also been emphasized. 相似文献
264.
Wong KL Lin X Kwon KY Pawin G Rao BV Liu A Bartels L Stolbov S Rahman TS 《Langmuir : the ACS journal of surfaces and colloids》2004,20(25):10928-10934
Para-halosubstituted thiophenols (X-TPs, where X is Br, Cl, or F) form ordered islands and monolayers on Cu(111) at temperatures as low as 81 K. At incomplete coverages, all X-TPs adsorb with the dehydrogenated thiol group attached to the substrate and the substituted ring inclined toward the surface, as verified experimentally and theoretically. The structure of ordered islands has a pronounced dependence on the nature of the halogen substituent: while unsubstituted TP and pentafluoro-TP molecules do not self-assemble into extended ordered patterns at 81 K, X-TP molecules form a range of different structures which depend both on the size and electronegativity of the substituent, as well as on the coverage. 相似文献
265.
Intracellular delivery of enzymes is essential for protein-based diagnostic and therapeutic applications. Protein-spherical nucleic acids (ProSNAs) defined by protein core and dense shell of oligonucleotides have been demonstrated as a promising vehicle-free enzyme delivery platform. In this work, we reported a crosslinking strategy to vastly improve both delivery efficiency and intracellular sensor performance of ProSNA. By assembling individual ProSNA with lactate oxidase (LOX) core into a nanoscale particle, termed as crosslinked SNA (X-SNA), the enzyme delivery efficiency increased up to 5–6 times higher. The LOX X-SNA was later demonstrated as a ratiometric probe for quantitative detection of lactate in living cells. More importantly, X-SNA probe showed significantly improved sensor performance with signal-to-noise ratio 4 times as high as ProSNA when detecting intracellular lactate.By crosslinking protein spherical nucleic acid (SNA) into a supramolecular architecture X-SNA, the intracellular enzyme delivery efficiency was significantly enhanced, showing 3–4 times higher signal-to-noise ratio in detecting intracellular lactate. 相似文献
266.
Peng Chen Xiaojun Luo Guanqi Dai Yuchuan Jiang Yue Luo Shuang Peng Hao Wang Penghui Xie Chen Qu Wenyu Lin Jian Hong Xue Ning Aimin Li 《Experimental & molecular medicine》2020,52(7):1062
Dexmedetomidine (DEX) is an anesthetic that is widely used in the clinic, and it has been reported to exhibit paradoxical effects in the progression of multiple solid tumors. In this study, we sought to explore the mechanism by which DEX regulates hepatocellular carcinoma (HCC) progression underlying liver fibrosis. We determined the effects of DEX on tumor progression in an orthotopic HCC mouse model of fibrotic liver. A coculture system and a subcutaneous xenograft model involving coimplantation of mouse hepatoma cells (H22) and primary activated hepatic stellate cells (aHSCs) were used to study the effects of DEX on HCC progression. We found that in the preclinical mouse model of liver fibrosis, DEX treatment significantly shortened median survival time and promoted tumor growth, intrahepatic metastasis and pulmonary metastasis. The DEX receptor (ADRA2A) was mainly expressed in aHSCs but was barely detected in HCC cells. DEX dramatically reinforced HCC malignant behaviors in the presence of aHSCs in both the coculture system and the coimplantation mouse model, but DEX alone exerted no significant effects on the malignancy of HCC. Mechanistically, DEX induced IL-6 secretion from aHSCs and promoted HCC progression via STAT3 activation. Our findings provide evidence that the clinical application of DEX may cause undesirable side effects in HCC patients with liver fibrosis.Subject terms: Cancer microenvironment, Cell growth 相似文献
267.
Summary Three novel heterotrinuclear complexes have been prepared, [Cu2(oxdn)2Zn](ClO4)2 (1) and [Cu2(oxdn)2-M(H2O)2](ClO4)2 with M=Mn (2) and Co (3) [oxdn-oxamidobis (propionato)], and characterized by spectral data. The temperature dependence of the magnetic susceptibilities of (2) and (3) has been studied in the 4–300K range, and the exchange integrals J=–20.90cm–1 for (2) and J=–62.36cm–1 for (3) calculated. These results are commensurate with antiferromagnetic interactions between the adjacent metal ions. 相似文献
268.
269.
The vibrational distribution of CO produced from the following two electronic-to-vibrational energy transfer reactions: have been determined by means of infrared resonance absorption measurements employing a cw CO laser. The CO molecules formed in both reactions were found to be vibrationally excited up to the limits of available electronic energies carried by the excited atoms. A similar result was also observed in the Br(42P) + CO reaction, in which absorption occurred only in the 1 → 2 band. For the O* + CO reaction the efficiency of E → V energy transfer was determined to be 16%. Our present results were found to be inconsistent with the impulsive (half-collision) model. 相似文献
270.
Magnetically recoverable chiral catalysts immobilized on magnetite nanoparticles for asymmetric hydrogenation of aromatic ketones 总被引:1,自引:0,他引:1
Novel heterogenized asymmetric catalysts were synthesized by immobilizing preformed Ru catalysts on magnetite nanoparticles via the phosphonate functionality and were characterized by a variety of techniques, including TEM, magnetization, and XRD. These nanoparticle-supported chiral catalysts were used for enantioselective heterogeneous asymmetric hydrogenation of aromatic ketones with very high enantiomeric excess values of up to 98.0%. The immobilized catalysts were easily recycled by magnetic decantation and reused for up to 14 times without loss of activity and enantioselectivity. Orthogonal nature of the present catalyst immobilization approach should allow the design of other superparamagnetic nanoparticle-supported asymmetric catalysts for a wide range of organic transformations. 相似文献