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211.
以作者开发的从蛋白质结合部位推导出其界面所具有的疏水性质和氢键性质的计算程序PP_SITE为基础,利用蛋白质结构数据库(PDB),对蛋白质-蛋白质相互作用界面进行了统计分析.从PDB中挑出非冗余的链间相互作用对,计算出这个数据集中所有链间界面的疏水和氢键相互作用特征.对得到的界面特征进行统计分析,寻找能够明显聚类的界面特征.结果表明,界面大小、氢键和疏水相互作用在界面所占比例以及疏水相互作用的集中程度可以作为分类的依据. 相似文献
212.
Chiral quaternary ammonium salts derived from cinchonidine have been applied to catalyze the stereoselective iodolactonizations of trans-5-aryl-4-pentenoic acids leading to a mixture of two regioselectively iodolactonized products with fair to excellent yield (37-98%) and moderate enantioselectivity (exo = 42.0% ee, endo = 31.0% ee) under mild conditions. This work is the first example of asymmetric iodolactonization reaction in the presence of less than a stoichiometric amount of chiral reagent. 相似文献
213.
Deng Y Wang C Shen X Yang W Jin L Gao H Fu S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(20):6006-6013
Novel functional microspheres with multistimuli-responsive properties have been prepared and characterized. The as-prepared microspheres respond to an external magnetic field, environmental temperature, and ultraviolet radiation. The in vitro drug-loading efficiency and drug-release behavior of these microspheres demonstrated that they could be used as drug carriers for drug controlled release. The results of in vivo distribution investigations of these microspheres showed that they exhibit a high magnetic-targeting effect, which holds promise for applications in various fields such as magnetic drug targeting and tissue labeling, among others. 相似文献
214.
The reaction of the cluster Os3(CO)10(μ-H)(μ-γ-C5H3O2) (1) with a number of alkynes under thermal or visible light irradiation conditions, afforded in most cases the dinuclear complexes Os2(CO)6(μ-γ-C5H3O2)(μ-LH) (L=PhCCPh, tBuCCH, tBuCCMe or EtCCEt) (2) or the trinuclear chain complexes Os3(CO)9(μ-H)(μ-γ-C5H3O2)(μ-RCCHC6H4) (R=H, Ph) (3). In the case of PhCCPh, a new isomer of Os3(CO)8(PhCCPh)2, viz., Os3(CO)8(μ-PhCCPh)(μ-PhCCHC6H4) (7) has been isolated and characterised. 相似文献
215.
Jian X. Gao Jian C. Wang Chong L. Song T. Liu Tian D. Hu Ya N. Xie J. Zhang G. Wang H. Yang 《Journal of solution chemistry》2006,35(1):113-119
NMR spectroscopy was used to show that the symmetry of the crown ether bis(C6) is increased by an increase of the alkali metal
cation radius. The EXAFS spectrum demonstrates that a seven oxygen atom coordinated configuration is present in the bis(C6)/Cs+/NPME system, where NPME denotes o-nitrophenylmethyl ether. The seventh oxygen in this complex, besides the six crown ether oxygens of bis(C6), may come either
from a H2O molecule or an NO3− ion. 相似文献
216.
A polyaluminum chloride (PAC) sample was prepared using a slow alkaline titration method. The Bio-Gel P-100 gel column chromatographic
technique was used to separate and characterize the various forms of aluminum present in the prepared PAC solution. The effluents
from a gel column were monitored using online chemical method: Al-Ferron timed complexation spectrophotometry and by 27Al nuclear magnetic resonance (NMR) spectroscopy. Effects of different experimental conditions such as eluent flow rate, ionic
strength and pH on separation of Al13 were investigated. Experimental results indicated that molecule size exclusion was not the only parameter affecting the column
chromatographic separation efficiency of Al13 but molecule charge as well. Reducing the eluent flow rate, increasing the ionic strength and suitable pH resulted in increase
in the separation efficiency. Experimental results clearly indicated that by varying the experimental conditions, it is possible
to produce pure Al13 species using a gel column chromatographic technique. 相似文献
217.
A polyaluminum chloride (PAC) sample was prepared using a slow alkaline titration method. The Bio-Gel P-100 gel column chromatographic technique was used to separate and characterize the various forms of aluminum present in the prepared PAC solution. The effluents from a gel column were monitored using online chemical method: Al-Ferron timed complexation spectrophotometry and by 27Al nuclear magnetic resonance (NMR) spectroscopy. Effects of different experimental conditions such as eluent flow rate, ionic strength and pH on separation of Al13 were investigated. Experimental results indicated that molecule size exclusion was not the only parameter affecting the column chromatographic separation efficiency of Al13 but molecule charge as well. Reducing the eluent flow rate, increasing the ionic strength and suitable pH resulted in increase in the separation efficiency. Experimental results clearly indicated that by varying the experimental conditions, it is possible to produce pure Al13 species using a gel column chromatographic technique. 相似文献
218.
Interactive effects of ultraviolet-B radiation and temperature on cotton physiology, growth, development and hyperspectral reflectance 总被引:1,自引:0,他引:1
Current conditions of 2-11 kJ m(-2) day(-1) of UV-B radiation and temperatures of >30 degrees C during flowering in cotton cultivated regions are projected to increase in the future. A controlled environment study was conducted in sunlit growth chambers to determine the effects of UV-B radiation and temperature on physiology, growth, development and leaf hyperspectral reflectance of cotton. Plants were grown in the growth chambers at three day/night temperatures (24/16 degrees C, 30/22 degrees C and 36/28 degrees C) and three levels of UV-B radiation (0, 7 and 14 kJ m(-2) day(-1)) at each temperature from emergence to 79 days under optimum nutrient and water conditions. Increases in main stem node number and the node of first fruiting branch and decrease in duration to first flower bud (square) and flower were recorded with increase in temperature. Main effects of temperature and UV-B radiation were significant for net photosynthetic rates, stomatal conductance, total chlorophyll and carotenoid concentrations of uppermost, fully expanded leaves during squaring and flowering. A significant interaction between temperature and UV-B radiation was detected for total biomass and its components. The UV-B radiation of 7 kJ m(-2) day(-1) reduced boll yield by 68% and 97% at 30/22 degrees C and 36/28 degrees C, respectively, compared with yield at 0 kJ m(-2) day(-1) and 30/22 degrees C. No bolls were produced in the three temperature treatments under 14 kJ m(-2) day(-1) UV-B radiation. The first-order interactions between temperature, UV-B radiation and leaf age were significant for leaf reflectance. This study suggests a growth- and process-related temperature dependence of sensitivity to UV-B radiation. 相似文献
219.
The interaction between gatifloxacin mesylate (GM) and salmon sperm DNA was studied by fluorescence spectrometry and ultra‐violet (UV) spectrometry. Additions of salmon sperm DNA to GM solution resulted in its strong fluorescence quenching and UV absorbance decrease due to the strong interaction between GM and salmon sperm DNA. Both the maximum fluorescence emission wavelength and the maximum UV absorbance wavelength of GM did not change with the increasing concentration of salmon sperm DNA, indicating no intercalative binding existed between them. The Stern‐Volmer plot indicated that the fluorescence‐quenching constant at different temperatures or different salmon sperm DNA concentration ranges was different. Effects of ionic strength and I? on the fluorescence quenching of GM by salmon sperm DNA indicated that electrostatic interaction and groove binding coexisted between them. 相似文献
220.