排序方式: 共有34条查询结果,搜索用时 15 毫秒
1.
Mirjana Popsavin Vesna Kojić Saša Spaić Miloš Svirčev Gordana Bogdanović Dimitar Jakimov Lidija Aleksić Velimir Popsavin 《Tetrahedron》2014
Tiazofurin analogues bearing a 5-hydroxymethyl-2-methyl-tetrahydrofuro[2,3-d][1,3]dioxol-6-ol moiety as a sugar mimic (2 and 3), and two novel thiazole-based acyclo-C-nucleosides 4 and 16 have been synthesized in multistep sequences starting from d-xylose (compounds 2 and 3) or from d-arabinose (compounds 4 and 16). All synthesized analogues showed potent in vitro antitumour activities against a panel of human tumour cell lines. Flow cytometry data suggest that cytotoxic effects of analogues 2–4 and 16 in the culture of K562 cells might be mediated by apoptosis. It was also found that these analogues induced changes in cell cycle distribution of K562 cells. Results of western blot analysis (upregulation of Bax and downregulation of Bcl-2, activation of caspase-3 and the presence of a PARP cleavage product) suggest that tiazofurin mimics (2–4 and 16) in K562 cells induced apoptosis in a caspase-dependent way. 相似文献
2.
Surajit?Dasgupta Neven?Bilic Tapas?K.?DasEmail author 《General Relativity and Gravitation》2005,37(11):1877-1890
We demonstrate that a spherical accretion onto astrophysical black holes, under the influence of Newtonian or various post-Newtonian
pseudo-Schwarzschild gravitational potentials, may constitute a concrete example of classical analogue gravity naturally found
in the Universe. We analytically calculate the corresponding analogue Hawking temperature as a function of the minimum number
of physical parameters governing the accretion flow. We study both the polytropic and the isothermal accretion. We show that
unlike in a general relativistic spherical accretion, analogue white hole solutions can never be obtained in such post-Newtonian
systems. We also show that an isothermal spherical accretion is a remarkably simple example in which the only one information–the
temperature of the fluid, is sufficient to completely describe an analogue gravity system. For both types of accretion, the
analogue Hawking temperature may become higher than the usual Hawking temperature. However, the analogue Hawking temperature
for accreting astrophysical black holes is considerably lower compared with the temperature of the accreting fluid. 相似文献
3.
Brian M. Gallagher Jr. Hongjuan Zhao Marc Pesant Francis G. Fang 《Tetrahedron letters》2005,46(6):923-926
A strategy is outlined which enables preparation of novel laulimalide analogues at C.8 and C.11. A representative analogue, 8-(S)-methoxy-11-desmethyl laulimalide, was synthesized via this route. 相似文献
4.
Simultaneous downlink performance improvement and uplink wavelength reuse in a full-duplex millimeter-wave (MMW) radio-over-fiber (RoF) system by using a simple and cost-effective all-fiber optical interleaver are proposed and demonstrated. The MMW RoF downlink performance improvement is based on suppressing optical carrier-to-sideband ratio (OCSR), with which the mechanism is confirmed by theoretic analysis and derived experimental results. Measured results show that, by suppressing OCSR using a fabricated all-fiber optical interleaver, the downlink optical receiver sensitivity is improved about 2.1 dB. The downlink data rate is 1.25 Gbit/s and the carrier frequency is 58.1 GHz; the link consists of 6 km optical single-mode fiber and 1 m wireless connection. On the other hand, with the interleaver suppressing downlink OCSR, simultaneously an optical carrier is recovered from the RoF downlink and is reused for RoF uplink transmission. The uplink is operated at 62.9 GHz and the data rate is the same 1.25 Gbit/s. With the recovered optical carrier, a laser-free remote access point is achieved. The principle, structure, and fabrication of an all-fiber optical interleaver are also presented in this paper. 相似文献
5.
以三聚氰胺(MAM)为类模板分子,甲基丙烯酸(MAA)为功能单体,二甲基丙烯酸乙二醇酯(EDMA)为交联剂,聚己二醇(PEG400)为致孔剂,原位聚合法制备了对三甲氧苄啶(TMP)有较强选择性吸附作用的分子印迹(MIP)整体柱.以该MIP整体柱为高效液相色谱柱,考察了其在不同色谱流动相组成条件下对TMP的识别性能.结果显示,MIP整体柱在甲醇、乙腈、水等条件下能够吸附TMP而不出峰.可以利用MIP整体.柱在甲醇-水( 80:20,V/V)中在线选择性吸附(或富集)TMP,然后将流动相转换为甲醇进一步除去疏水性杂质,最后用强洗脱剂洗脱TMP出峰.MIP整体柱线检测人血清中TMP的工作曲线为A=42.8c 3.03(r=0.9994);线性范围为8.3~93.8 mg/L;检出限为0.14 mg/L. 相似文献
6.
IntroductionγAminobutyricacid(GABA)isrecognizedasthe principalbraininhibitoryneurotransmitter.GABAup takefromthesynapticcleftisoneoftheimportant mechanismsintheregulationofGABAactivity.Inhibi tionoftheuptakeofGABAbypotentandselectivein hibitorsoftheGABAt… 相似文献
7.
3-Ethyl 5-methyl 2-[(2-(2-(2-aminoethoxy)ethoxy)ethoxy)methyl]-4-(2-chlorophenyl)-6-methyl-1,4-dihydropyridine-3,5-dicarboxylate as new analogue of amlodipine was prepared in five steps with an overall yield of 22%. The 1,4-dihydropyridine nucleus was built in two steps via Knoevenagel reaction and the amino group of this analogue has been prepared in good yield by Staudinger reduction of the azido 1,4-dihydropyridine precursor in the last step. 相似文献
8.
罂粟花粉十七肽类似物和片段的合成及其抗肿瘤活性研究 总被引:7,自引:0,他引:7
以从罂粟花粉中分离得到的具有促免疫和抗肿瘤活性的十七肽为先导化合物,设计了4个类似物和3个片段,并用固相法合成,通过CD谱测定了它们在溶液中的初级二级结构,同时测定了它们对人胃癌和人膀胱癌肿瘤细胞的抑制活性,初步讨论了构效关系. 相似文献
9.
10.
Naoyuki Kotoku Shinichi FujiokaChiaki Nakata Masaki YamadaYuji Sumii Takashi KawachiMasayoshi Arai Motomasa Kobayashi 《Tetrahedron》2011,67(35):6673-6678
Structure-activity relationship of furospinosulin-1 (1), a hypoxia-selective growth inhibitor isolated from marine sponge, was investigated. Concise synthetic method of 1 was developed, and some structurally modified analogues were prepared. Biological evaluation of them revealed that the whole chemical structure was important for the hypoxia-selective growth inhibitory activity of 1. Among prepared, the desmethyl analogue 30 showed excellent hypoxia-selective inhibitory activity similar to that of 1 and also exhibited in vivo anti-tumor activity with oral administration. 相似文献