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971.
Maria Bykhovskaia Boris Gelmont Tatiana Globus Dwight L. Woolard Alan C. Samuels Tap Ha Duong Krystyna Zakrzewska 《Theoretical chemistry accounts》2001,106(1-2):22-27
We present a computational method which couples normal mode analysis in internal coordinates of a molecule with very far
IR spectroscopy. The analytical expression for the dependence of IR absorption on frequency incorporates frequencies and optical
activities of each normal mode. In order to predict far-IR spectra of a molecule we evaluate the optical activity of each
normal mode. This optical activity is determined by the vibration amplitude of the dipole moment produced by a normal mode.
We calculated normal modes of DNA double-helical fragments (dA)12 · (dT)12 and (dA-dT)6 · (dA-dT)6 and evaluated their optical activities. These were found to be very sensitive to the DNA base-pair sequence. The positions
of the resonance peaks in the calculated absorption spectrum of (dA)12 · (dT)12 are in a good agreement with those obtained by Fourier transform IR spectroscopy (Powell JW et al. 1987 Phys Rev A 35: 3929–3939).
Received: 20 June 2000 / Accepted: 5 January 2001/ Published online: 3 May 2001 相似文献
972.
Yongqiang Ma Jinshan Li Zhenai Xuan Runchang Liu 《Journal of organometallic chemistry》2001,620(1-2):235-242
A series of novel arylantimony(V) triphenylgermanylpropionates with the formula (Ph3GeCHR1CHR2CO2)nSbAr(5−n) (R1=H, Ph; R2=H, CH3; n=1, 2) were synthesized and characterized by elemental analysis, IR, 1H-NMR, 13C-NMR and mass spectroscopy. The crystal structures of Ph3GeCH(Ph)CH2CO2SbPh4 and [Ph3GeCH2CH(CH3)CO2]2Sb(4-ClC6H4)3 were determined by X-ray diffraction. The in vitro antitumor activities of some selected compounds against five cancer cells are reported. 相似文献
973.
在作黄酮和黄酮甙的快原子轰击质谱时,如果同时加入氯化钠和氯化钾两种碱金属盐,就会在谱图中同时出现两个强峰,由于这两个峰相差16个原子质量单位,很容量辨认,并且发现在其谱图中找不到明显的碎片离子和Na^+和K^+的加合离子,而只有其分子和K^+和Na^+的加合,所以很容易在FAB谱中识别它们,因而就可以快速,准确地确定样品的分子量。 相似文献
974.
Sabrina Aufar Salma Cuong M.Q. Le Dong Woo Kim Xuan Thang Cao Yeon Tae Jeong 《Molecular Crystals and Liquid Crystals》2018,662(1):188-196
ABSTRACTA well-defined amphiphilic block copolymer, poly (ethylene oxide)-b-(poly (furfuryl methacrylate) (PEO-b-PFMA) was prepared by single electron transfer living radical polymerization using tris(dimethylamino)ethyl amine (Me6TREN) as a ligand. The block copolymer formed sub-100 nm micelles in water with PEO as a shell and PFMA as a core. Diels–Alder click type reaction was employed to form core-crosslinked micelles using a diselenide-containing crosslinker without any catalyst. The block copolymer and micelles were characterized by gel permeation chromatography, nuclear magnetic resonance, Fourier-transform infrared spectroscopy, dynamic light scattering analysis and transmission electron microscopy. The stability of core-crosslinked micelles under reductive-oxidative condition was also investigated. The diselenide crosslinked micelles displayed good stability against extensive dilution but decomposed under the presence of hydrogen peroxide or glutathione. The redox responsive core-crosslinked micelles can be a promising carrier for drug delivery applications. 相似文献
975.
976.
977.
Xiahui Lin Shuya Liu Xuan Zhang Rong Zhu Shan Chen Xiaoyuan Chen Jibin Song Huanghao Yang 《Angewandte Chemie (International ed. in English)》2020,59(4):1682-1688
Sonodynamic therapy (SDT) has the advantages of high penetration, non‐invasiveness, and controllability, and it is suitable for deep‐seated tumors. However, there is still a lack of effective sonosensitizers with high sensitivity, safety, and penetration. Now, ultrasound (US) and glutathione (GSH) dual responsive vesicles of Janus Au‐MnO nanoparticles (JNPs) were coated with PEG and a ROS‐sensitive polymer. Upon US irradiation, the vesicles were disassembled into small Janus Au‐MnO nanoparticles (NPs) with promoted penetration ability. Subsequently, GSH‐triggered MnO degradation simultaneously released smaller Au NPs as numerous cavitation nucleation sites and Mn2+ for chemodynamic therapy (CDT), resulting in enhanced reactive oxygen species (ROS) generation. This also allowed dual‐modality photoacoustic imaging in the second near‐infrared (NIR) window and T1‐MR imaging due to the released Mn2+, and inhibited orthotopic liver tumor growth via synergistic SDT/CDT. 相似文献
978.
Chao-Qun Wang Li-Wei Yi Lin Zhao Yu-Zhen Zhou Fang Guo Yu-Shu Huo Da-Qing Zhao Feng Xu Xuan Wang Shao-Qing Cai 《Molecules (Basel, Switzerland)》2021,26(11)
Wild ginseng (W-GS), ginseng under forest (F-GS, planted in mountain forest and growing in natural environment), and cultivated ginseng (C-GS) were compared via HPLC-DAD and HPLC-IT-TOF-MSn. A total of 199 saponins, including 16 potential new compounds, were tentatively identified from 100 mg W-GS (177 saponins in W-GS with 11 new compounds), F-GS (56 saponins with 1 new compound), and C-GS (60 saponins with 6 new compounds). There were 21 saponins detected from all the W-GS, F-GS, and C-GS. Fifty saponins were only detected from W-GS, including 23 saponins found in ginseng for the first time. Contents of ginsenosides Re (12.36–13.91 mg/g), Rh1 (7.46–7.65 mg/g), Rd (12.94–12.98 mg/g), and the total contents (50.52–55.51 mg/g) of Rg1, Re, Rf, Rb1, Rg2, Rh1, and Rd in W-GS were remarkably higher than those in F-GS (Re 1.22–3.50 mg/g, Rh1 0.15–1.49 mg/g, Rd 0.19–1.49 mg/g, total 5.69–18.74 mg/g), and C-GS (Re 0.30–3.45 mg/g, Rh1 0.05–3.42 mg/g, Rd 0.17–1.68 mg/g, total 2.99–19.55 mg/g). Contents of Re and Rf were significantly higher in F-GS than those in C-GS (p < 0.05). Using the contents of Re, Rf, or Rb1, approximately a half number of cultivated ginseng samples could be identified from ginseng under forest. Contents of Rg1, Re, Rg2, Rh1, as well as the total contents of the seven ginsenosides were highest in ginseng older than 15 years, middle–high in ginseng between 10 to 15 years old, and lowest in ginseng younger than 10 years. Contents of Rg1, Re, Rf, Rb1, Rg2, and the total of seven ginsenosides were significantly related to the growing ages of ginseng (p < 0.10). Similarities of chromatographic fingerprints to W-GS were significantly higher (p < 0.05) for F-GS (median: 0.824) than C-GS (median: 0.745). A characteristic peak pattern in fingerprint was also discovered for distinguishing three types of ginseng. Conclusively, wild ginseng was remarkably superior to ginseng under forest and cultivated ginseng, with ginseng under forest slightly closer to wild ginseng than cultivated ginseng. The differences among wild ginseng, ginseng under forest, and cultivated ginseng in saponin compositions and contents of ginsenosides were mainly attributed to their growing ages. 相似文献
979.
新的4’-去甲表鬼臼衍生物的合成及其抗癌活性 总被引:1,自引:0,他引:1
根据鬼臼毒衍生物和5-氟尿嘧啶的抗癌机理和构效关系,合成了7个新的4β- 5-氟尿嘧啶取代-4’-去甲表鬼鬼臼毒衍生物。在抑制金属基质蛋白酶I和胶原酶I 活性测试中,化合物2.4和2.6的抑制活性比鬼臼乙叉甙(VP-16)和5-氟尿嘧啶( 5-Fu)强的3倍和5倍,在治疗癌细胞转移方面值得进一步探讨。 相似文献
980.
直链低碳α-烯烃是生产线性低密度聚乙烯的共聚单体及合成高级润滑油和一些精细化学品的中间体,通过乙烯齐聚反应生成直链α-烯烃是目前工业上重要的生产方法,近几年来使乙烯齐聚成α-烯烃的含二或三齿配体后过渡金属催化剂的催化特性受到人们很大的关注。 相似文献