Kinetic energy decomposition scheme based on information theory

We proposed a novel kinetic energy decomposition analysis based on information theory. Since the Hirshfeld partitioning for electron densities can be formulated in terms of Kullback–Leibler information deficiency in information theory, a similar partitioning for kinetic energy densities was newly proposed. The numerical assessments confirm that the current kinetic energy decomposition scheme provides reasonable chemical pictures for ionic and covalent molecules, and can also estimate atomic energies using a correction with viral ratios.     

Purification of recombinant green fluorescent protein by three-phase partitioning

The technique of three-phase partitioning (TPP) was used to purify the green fluorescent protein (GFP) in a single step. TPP uses a combination of ammonium sulphate and tert-butanol to precipitate proteins from their crude extracts. In the first round of TPP with 20% ammonium sulphate saturation at the ratio of crude to tert-butanol 1:1 (v/v), most of the GFP remains in the lower aqueous phase. When subjected to a second round of TPP with 60% ammonium sulphate saturation at the ratio of crude to tert-butanol 1:2 (v/v) gives 78% recovery of GFP with a 20-fold purification. The sodium dodecyl sulphate-polyacrylamide gel electrophoretic (SDS-PAGE) analysis of purified preparation shows single band. The fluorescence excitation and emission spectra agreed with values reported in literature.     

Evaluation of recombinant green fluorescent protein, under various culture conditions and purification with HiTrap hydrophobic interaction chromatography resins

To determine the influence of various culture conditions, transformed cells of Escherichia coli expressing recombinant green fluorescent protein (GFPuv) were grown in nine cultures with four variable conditions (storage of inoculated broth at 4°C prior to incubation, agitation speed, isopropyl-β-d-thiogalactopyranoside [IPTG] concentration, and induction time). The pelleted cells were resuspended in extraction buffer and subjected to the three-phase partitioning (TPP) extraction method. To determine the most appropriate purification resin, protein extracts were eluted through one of four types of HiTrap hydrophobic interaction chromatography (HIC) columns prepacked with methyl, butyl, octyl, or phenyl resins and analyzed further on a 12% sodium dodecylsulfatepolyacrylamidegel. With Coomassie staining, a single band between 27 (standard GFPuv) and 29 kDa (molecular weight standard) was visualized for every HIC column sample. TPP extraction with HIC elution provided about 90% of the GFPuv recovered and eight-fold GFPuv enrichment related to the specific mass. Rotary speed and IPTG concentration showed, respectively, greater negative and positive influences on GFPuv expression at the beginning of the logarithmic phase for the set culture conditions (37°C, 24-h incubation).     

外加盐作用形成的正负离子表面活性剂双水相

癸基三乙基溴化铵-癸基磺酸钠（C10NE-C10SO3）等摩尔混合均相体系（即使在表面活性剂总浓度高达0.2 mol•L－1时仍然可形成稳定的均相溶液）在外加盐NaF、Na2SO4和Na3PO4的作用下可自发分离成两个水相（双水相）.研究了该类双水相体系的形成、相行为及其对牛血清蛋白（BSA）的分配，并与普通的正负离子表面活性剂混合双水相体系进行了比较.结果表明，该类双水相体系克服了普通的正负离子表面活性剂混合双水相体系的一些不足，具有一些独特的优点.该类双水相体系的相行为可以通过外加盐进行调控,通过外加盐的种类来调控和优化BSA的分配行为.图1表2参8     

Dispersion polymerization of styrene in ethanol–water media: Monomer partitioning behavior and locus of polymerization

A simulation model has been developed to predict the partitioning behavior of styrene in dispersion polymerization in ethanol–water mixtures. The composition of both the continuous phase and the dispersed phase are quantitatively estimated throughout the polymerization process. The presence of water in the system causes a considerable increase of the styrene partitioning in favor of the particles. Thus, at 70°C and for an initial composition of ethanol/water/styrene = 63.3/26.9/9.8, the concentration of styrene in the particles is about 4.8 times higher than that in the serum instead of about one in pure ethanol. The higher the polymerization temperature, the lower the styrene concentration in the particles; the higher the initial styrene concentration, the higher the styrene concentration in the particles, whereas the partition coefficient is not largely effected. In contrast, neither the interfacial tension nor the final particle size do significantly alter the simulation results. The predicted data from this model have been successfully applied to clarify the mechanisms involved in dispersion polymerization, in terms of stabilization and of kinetic events. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36 : 325–335, 1998     

Study of gas-liquid partitioning of alkane solutes in several organic solvents by using principal component analysis and linear solvation energy relationships

Principal component analysis (PCA) was used to extract the number of factors which can describe the 737 gas-liquid partition coefficients of five linear, four branched, and two cyclic alkanes in 67 common solvents. Based on the reconstruction of partition coefficient data matrix, we concluded that the experimental dataset could readily be reduced to two relevant factors. Using only these two factors, there were no errors larger than 3%, 7 cases had errors larger than 2%, and in 34 cases, errors were between 1 and 2%. n-Hexane and ethylcyclohexane were chosen as the test factors, and all other partition coefficients were expressed in terms of these two test factors. Prediction of the logarithmic partition coefficient of these alkanes in seven chemically different solvents, which were originally excluded from the data matrix, was excellent: the root mean square error was 0.064, only in 11 cases the errors were larger than 1%, and only 3 had errors larger than 4%.Linear solvation energy relationships (LSERs) using both theoretical and empirical solvent parameters were used to explain the molecular interactions responsible for partition. Several combinations of parameters were tried but the standard deviations were not less than 0.31. This could be attributed to the model itself, imprecisions in the data matrix or in some of the LSER parameters. Solvent cohesive parameters and surface tension in combination with polarity-polarizability or dispersion parameters perform the best.Finally, the two principal component factors were rotated onto the most relevant physicochemical parameters that control the gas-liquid partitioning phenomena.     

从头计算方法比较研究B_2Au_4,Al_2Au_4和BAlAu_4的几何和电子结构(英文)

Au/H相似性的研究是现代化学中的一个热门话题.我们从理论上报道Au/H相似的新成员:共价化合物B2Au4,离子化合物Al2Au4和BAl Au4.采用密度泛函和波函数理论方法对比研究了缺电子体系B2Au4、Al2Au4和BAl Au4的几何和电子结构.详细讨论了它们基态结构的轨道、适应性自然密度划分(Ad NDP)和电子局域函数(ELF)分析.计算结果表明稍微扭曲变形的C2B2Au4是基态结构,在这个共价化合物中含有两个B―Au―B三中心二电子(3c-2e)键.然而C3vAl+(Al Au4)-和C3vAl+(BAu4)-被研究证明是含有三个X―Au―Al三中心二电子键的类盐化合物(在Al2Au4中X=Al,BAl Au4中X=B).Al2Au4和BAl Au4是至今为止首例报道的在离子缺电子体系中含有金桥键的化合物.同时计算了B2Au4-、Al2Au4-和BAl Au4-阴离子基态结构的绝热剥离能和垂直剥离能,为实验表征提供依据.文中报道的金桥键为共价键和离子键相结合的缺电子体系提供了一个有趣的键合模式,有助于设计含有高度分散金原子的新材料和催化剂.     

2DE‐based approach for estimation of number of protein species in a cell

Insufficient sensitivity of methods for detection of proteins at a single molecule level does not yet allow obtaining the whole image of human proteome. But to go further, we need at least to know the proteome size, or how many different protein species compose this proteome. This is the task that could be at least partially realized by the method described in this article. The approach used in our study is based on detection of protein spots in 2DE after staining by protein dyes with various sensitivities. As the different protein spots contain different protein species, counting the spots opens a way for estimation of number of protein species. The function representing the dependence of the number of protein spots on sensitivity or LOD of protein dyes was generated. And extrapolation of this function curve to theoretical point of the maximum sensitivity (detection of a single smallest polypeptide) allowed to counting the number of different molecules (polypeptide species) at the concentration level of a single polypeptide per proteome. Using this approach, it was estimated that the minimal numbers of protein species for model objects, Escherichia coli and Pirococcus furiosus, are 6200 and 3400, respectively. We expect a single human cell (HepG2) to contain minimum 70 000 protein species.