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991.
共聚焦激光扫描显微术研究天花粉蛋白对小鼠胚胎细胞的作用机制 总被引:2,自引:0,他引:2
天花粉蛋白是从中草药Ku楼根中根中取的一种核糖体失活蛋白,具有致流产、抗肿瘤和抗HIV功能。本文应用共聚焦激光扫描显微术结合特异性荧光探针2',7'-二氯荧光黄双乙酸酯和Fluo-3AM,观察了天花粉蛋白作用于小鼠胚胎细胞过程中活性氧自由基和细胞内钙离子浓度的变化。实验结果表明,天花粉蛋白能诱导小鼠胚胎细胞钙浓度升高和产生活性氧自由基,并且天花粉蛋白能有效抑制小鼠胚胎细胞的分裂,为天花粉蛋白的致流产提出了新的机制。 相似文献
992.
A class of processes for which the problem of species balance can be solved without using any assumptions concerning the mechanism of the chemical event of the reaction was found in the problem of species balance in the reaction zone. The mathematical statement of the problem in this case was discussed; it was shown that the solution is mainly determined by the system geometry. The method for reducing the problem to determination of the probability of species entering the chemical event zone is substantiated; this can be done by the Green function method. 相似文献
993.
非离子型微乳液对结晶紫-磷钼杂多酸光度分析的增敏作用 总被引:5,自引:1,他引:4
本文首次研究了非离子型O/W微乳液TritonX-100/n-C5H11OH/n-C9H20/H2O对结晶紫-磷钼杂多酸显色体系的增敏作用。结果表明,与相同含量胶束体系比较,微乳液介质体系中测定灵敏度增加二分之一。通过测定显色剂在微乳液及相应胶束体系中的分配系数KD、胶束位n和结合常数K,探讨了非离子型O/W微乳液对结晶紫-磷钼杂多酸显色体系的增敏作用机理。 相似文献
994.
The photochemical processes of aromatic amino acids were investigated in aqueous solution using acetone as photosensitizer by KrF (248 nm) laser flash photolysis. Laser-induced transient species were characterized according to kinetic analysis and quenching experiments. The intermediates recorded were assigned to the excited triplet state of tryptophan, the radicals of tryptophan and tyrosine. The excited triplet state of tryptophan produced via a triplet-triplet excitation transfer and the radicals arising from electron transfer reaction has been identified. Neither electron transfer nor energy transfer between triplet acetone and phenylalanine can occur in photolysis of phenylalanine aqueous solution which contains acetone. Furthermore, triplet acetone-induced radical transformation: Trp/N-Tyr→Trp-Tyr/O was observed directly in photolysis of dipeptide (Trp-Tyr) aqueous solution containing acetone, and the transformation resulting from intramolecular electron transfer was suggested. 相似文献
995.
多波长线性回归分光光度法同时测定磷和硅 总被引:1,自引:0,他引:1
以钼酸铵-Sb^3+-抗坏血酸为显色体系,详细考察了磷、硅的锑钼蓝杂多酸络合物的最佳形式条件,据此建立了多波长线顺归分光光度法同时测定磷、硅的新方法。该方法操作简便、快速、对多种环境水样中痕量磷、硅测定的相对标准偏差小于5%。测定结果与利用光度法分别测定的结果相吻合,相对误差小于10%。 相似文献
996.
W. Hoffbauer S. Wefing G. Klsters F. Frick M. Jansen 《Solid state nuclear magnetic resonance》1999,14(3-4)
The rotational dynamics of P4O6S and P4O7 in the solid state were studied by means of 31P NMR spectra of spinning and static powder samples in the temperature range of 153–295 K and 295–388 K, respectively. All spectra were simulated to confirm the type of the motion and to extract the time scales as a function of the temperature. Good agreement between experimental and theoretical data was obtained on the basis of a three-site jump model. For P4O6S, the activation energy and the pre-exponential factor derived from the lineshape simulations amount to 51(2) kJ/mol and 6(3)·1015 s−1. For P4O7, the spectral analysis yields an activation energy of 67(1) kJ/mol and a pre-exponential factor of 6(2)·1014 s−1. The dynamic behavior was checked independently by lineshape analyses under both MAS and static conditions. Activation energies are consistent within the errors for the lineshape analyses. Additionally, we have analyzed spin–lattice relaxation measurements, which show the correct trends for the activation energies. 相似文献
997.
用乙酸镍、2-乙基己酸镍、二乙基氯化铝、倍半乙基氯化铝等组成Ziegler-Natta催化剂催化丁烯齐聚.测定了二聚物组成,讨论了活性物种的形成过程,推导了反应机理. 相似文献
998.
K.R.Tsai 《高等学校化学研究》1993,9(3):264-268
Since the pioneer work of Keller and Bhasin on the oxidative coupling of methane, many catalyst systems, mostly based on the oxides or complex oxides of alkali metals, alkali earth metals and rare earth metals, have been developed. In some studies, halides, especially chlorides and bromides, have been added to these oxides in order to improve the catalvtic activitv and selectivity. howevek of 相似文献
999.
Georgiana Negru Laure Kamus Elena Bîcu Sergiu Shova Boualem Sendid Faustine Dubar Alina Ghinet 《Molecules (Basel, Switzerland)》2021,26(19)
The treatment of benzylidenemalononitriles with phenylhydrazines in refluxing ethanol did not provide pyrazole derivatives, but instead furnished hydrazones. The structure of hydrazones was secured by X-ray analysis. The chemical proof was also obtained by direct reaction of 3,4,5-trimethoxybenzaldehyde with 2,4-dichlorophenylhydrazine. Newly synthesized hydrazones were tested against eight Candida spp. strains in a dose response assay to determine the minimum inhibitory concentration (MIC99). Five compounds were identified as promising antifungal agents against Candida spp. (C. albicans SC5314, C. glabrata, C. tropicalis, C. parapsilosis and C. glabrata (R azoles)), with MIC99 values ranging from 16 to 32 µg/mL and selective antifungal activity over cytotoxicity. 相似文献
1000.
铈钼氧化物表面氧性质和催化性能 总被引:4,自引:0,他引:4
在甲苯选择性氧化制苯甲醛反应中,Mo基氧化物是一类重要的催化剂[1].通常的认识是反应物与催化剂表面晶格氧作用,并通过催化剂本身的还原和氧化的循环过程促使反应进行。生成产物.因此,催化剂表面不同氧物种的热脱附性能应与催化反应性能密切相关.对于Ce-Mo氧化物的TPD-MS研究,尚未见文献报导.为了能获得该方面的信息,本文应用程序升温脱附-质谱检测(TP-MS)联用技术,对Ce-Mo氧化物样品进行了表面氧TPD谱测定和动力学参量等计算,并试图与其催化性能进行关联.1实验部分1.1样品的制备和表征分别将一定质量的硝酸铈铵和仲… 相似文献