Interaction of cellulase with sodium dodecyl sulfate at critical micelle concentration level

The interactions between Trichoderma reesei cellulase and an anionic surfactant, sodium dodecyl sulfate (SDS), at critical micelle concentration level have been investigated using isothermal titration calorimetry, fluorescence spectroscopy, and circular dichroism. SDS micelles have dual interactions with cellulase: electrostatic at first and then hydrophobic interactions. When the concentration of SDS is smaller than 45.0 mM, SDS micelles cause a partial loss in the hydrolytic activity together with a steep decrease in the -helical content of cellulase. With further increasing the concentration of SDS, however, a re-formation of the -helical structure and a partial recovery of the hydrolytic activity of cellulase induced by SDS micelles are observed. Taken together, these results indicate that SDS micelles exert dual effects on cellulase through binding as both a denaturant and a recovery reagent.     

Quantitation of seven polyoxypregnane glycosides in Marsdenia tenacissima using reversed-phase high-performance liquid chromatography-evaporative light-scattering detection

A high-performance liquid chromatography coupled with an evaporative light scattering detector (HPLC-ELSD) has been developed for the simultaneous determination of seven polyoxypregnane glycosides, tenacissosides A, B, G, H, I and marsdenosides C, G, in the stem of Marsdenia tenacissima, a Chinese herbal medicine. With a C18 analytical column, the analytes were separated efficiently using methanol-water as the mobile phase in a gradient program. The method limits of detection ranged from ca. 0.3 microg for marsdenoside C to ca. 0.5 microg for marsdenoside G and the method limits of quantitation from 1.0 microg for marsdenoside C to 1.7 microg for marsdenoside G, respectively. The intra- and inter-day precisions of the method were evaluated and all were less than 4%. All the recoveries for the spiked analytes exceeded 90%. This method was successfully used to analyze 19 samples of the stem of M. tenacissima.     

在盐的水溶液中非电解质活度系数的研究(Ⅺ)——正丙酸和正丁酸在苯和盐水溶液间的分配

在25℃下分别测定正丙酸和正丁酸在苯相和纯水相中的分配比,以及在苯相和盐水溶液中的分配比,从而求出酸的活度系数。所用的盐有氯化锂、氯化钠、氯化钾、氯化锶、氯化钡、溴化锂、溴化钠、溴化钾等八种。对弱酸算出了未解离部分的活度系数。在所用盐浓度(0-1mol/l)范围内,作lgf_u-C_s图,都呈直线。比较直线的斜率,对正丙酸为:SrCl₂>BaCl₂>LiCl≈NaCl>LiBr≈NaBr>KCl>KBr。对正了酸为:SrCl₂>BaCl₂>NaCl≈LiC₁>NaBr≈KCl≈LiBr>KBr.指出小离子盐对小脂肪酸盐效应主要是静电力作用。     

IVSPlat 1.0: an integrated virtual screening platform with a molecular graphical interface

Background  

The virtual screening (VS) of lead compounds using molecular docking and pharmacophore detection is now an important tool in drug discovery. VS tasks typically require a combination of several software tools and a molecular graphics system. Thus, the integration of all the requisite tools in a single operating environment could reduce the complexity of running VS experiments. However, only a few freely available integrated software platforms have been developed.     

Rare earth‐doped calcium‐based magnetic catalysts for transesterification of glycerol to glycerol carbonate

Several rare earth‐doped, calcium‐based magnetic catalysts were prepared for the synthesis of glycerol carbonate. The basicity and basic strength analysis of the catalysts showed that the doping of rare earth improved the basicity of the catalysts, and the doping of lanthanum maximized it. In addition, with the doping of lanthanum, the particle size of the catalyst became smaller to promote the organic reactants near the active sites of catalysts, thereby effectively improving the performance. NiFe₂O₄@[CaO‐La₂O₃] shows better catalytic performance with 99.0% yield of glycerol carbonate compared to the other catalysts. The NiFe₂O₄@(CaO‐La₂O₃) could be reused in six cycles without significant loss in activity.     

甲烷单加氧酶活性化合物的体外重构

甲烷氧化菌中甲烷单加氧酶既能催化甲烷转化为甲醇,也能降解小分子含氯有机物.将甲烷单加氧酶组分进行基因重组表达,利用表达的组分重构酶活性化合物,测定了重构化合物的丙烯环氧化活性及对三氯乙烯和三氯甲烷的降解.结果显示:经过30℃、220 r/min、20 min降解,约有52%的三氯乙烯被降解;在32℃、220 r/min、8 h反应条件下,约有26%的三氯甲烷被降解;表明甲烷单加氧酶亚基组分表达正确,能够在微生物体外重构活性化合物.     

长中半径水平井钻柱接触摩擦阻力分析

用整体钻柱静力模型和间隙元法,分析了长中半径水平井钻柱的接触非线性问题,算出了钻柱与井壁接触摩擦阻力的分布,为水平井井眼轨道设计和施工提供了重要参数。     

柔性砷化镓薄膜太阳电池剥离(lift-off)技术研究

对柔性砷化镓薄膜太阳电池关键技术进行研究,通过对柔性衬底表面处理、外延片/柔性衬底键合、衬底剥离技术和柔性薄膜外延层器件工艺技术等进行研究,成功地将砷化镓电池外延层转移到柔性聚酰亚胺薄膜衬底上,研制出效率为30.5;(AM0,25℃)的柔性砷化镓薄膜太阳电池,其重量比功率达到2153 W/kg,为将来卫星及临近空间飞行器的应用打下技术基础.     

基于彩色结构光的自由曲面三维重建方法

彩色结构光三维重建过程中,系统的非线性耦合以及待测曲面的拓扑结构等均会对结构光解码产生影响,从而导致调制条纹漏检和颜色码误识别.为解决这一问题,提出一种基于彩色编码结构光的三维重建方法.利用YUV颜色通道对调制条纹进行滤波差分投影处理,通过调制条纹的波形分布提取中心特征线;利用颜色聚类方法精确获取调制条纹的颜色码信息值...     

L2×L2中的一类无穷维Hamilton算子的剩余谱

该文得到了一类无穷维Hamilton算子的剩余谱和点谱存在的几个判别准则,从而给出 了求其剩余谱和点谱的方法．在此基础上构造了L2×L2中无穷维Hamilton算子的剩余谱 非空的具体例子,从而进一步验证了判别准则的有效性．