Refolding of a Staphylokinase Variant Y1-Sak by Reverse Dilution

To develop more potent thrombolytic agents with fibrinolytic and antiplatelet aggregation activity, staphylokinase (Sak) variant Y1-Sak, a recombinant mutant of the Staphylococcus aureus protein Sak, was constructed. Y1-Sak formed an insoluble inclusion body when overexpressed in Escherichia coli strain JF1125. To obtain an optimized refolding process, dilution refolding was used to optimize refolding conditions. The results revealed that additive l-arginine and refolding temperature played critical roles in the refolding of Y1-Sak. Subsequently, two refolding methods, gel filtration and reverse dilution, were investigated to refold Y1-Sak. The results indicated that the fibrinolytic activity and recovery of Y1-Sak from gel filtration were lower than those from reverse dilution. Reverse dilution refolding successfully reduced the side reaction of refolding with the help of l-arginine, and the fibrinolytic activity and recovery of Y1-Sak were significantly improved. Functional analysis revealed that refolded Y1-Sak by reverse dilution possessed fibrinolytic and antiplatelet aggregation activities. Moreover, the immunogenicity of Y1-Sak was significantly reduced.     

边界耦合的牛顿渗流方程组解的整体存在与爆破

本文研究了由边界条件耦合的多维牛顿渗流方程组解的长时间行为.利用构造的多种上下解,得到了整体存在临界曲线与Fujita临界曲线.     

Dynamic interactive membranes with pressure-driven tunable porosity and self-healing ability

When pressure is applied to dynamic interactive membranes consisting of micelles composed of a triblock copolymer, their morphologies can be fine-tuned. Membranes with a range of porosities are accessible which can regulate and thereby control filtration performance and also display effective autonomous healing.     

Determination of the Molecular Weight of Extracellular Ribonuclease Isoenzymes from Aspergillus Niger in Crude Extracts by Thin Layer Gel Filtration and Polyacrylamide Gel Electrophoresis

Abstract

The extracellular ribonucleases from Asperqillus niger culture medium were fractionated according to their molecular weight by thin layer gel filtration through Sephadex G100 superfine and the enzyme activity was detected by a standard staining technique on a replica print paper. Another replica paper was laid onto the top of a polyacrylamide gel and the absorbed proteins were separated by electrophoresis. By comparing the electrophoretic pattern with that of a control not subjected to gel filtration, the molecular weight of each isoenzyme in the crude extract could be determined. Gel electrophoresis however, is only used to establish the correspondence between the original electrophoretic pattern of the isoenzymes in the crude preparation and that detected on the replica print paper taken after the thin layer gel filtration run. There was good agreement between the values obtained for the crude and purified enzymes.     

Hierarchical Nitrogen‐Doped Flowerlike ZnO Nanostructure and Its Multifunctional Environmental Applications

Hierarchical nitrogen‐doped ZnO flowerlike nanostructures were synthesized on a large scale. These nanostructures were characterized by FESEM, HRTEM, XRD, FTIR, XPS, and TGA, and their suitability for multifunctional environmental applications was investigated. The experimental results demonstrated that the hierarchical N‐doped ZnO flowerlike nanostructure enhances the photodegradation of methyl blue (MB) and acid orange 7 (AO7) by presenting a large specific surface area and high light utilization rate, inhibits the growth of bacteria without light irradiation, and increases the permeate flux when used in a membrane filtration system. These advantages of the hierarchical N‐doped ZnO flowerlike nanostructure brings benefits to the environmental application fields.     

Discrete-time local risk minimization of payment processes and applications to equity-linked life-insurance contracts

We develop a theory of local risk minimization for payment processes in discrete time, and apply this theory to the pricing and hedging of equity-linked life-insurance contracts. Thus, we extend the work of Møller (2001a) in several directions: from risk minimization (which is done under a martingale measure) to local risk minimization (which is done under an arbitrary measure), from single claims to payment processes, from complete financial markets to possibly incomplete financial markets, from a single risky asset to several risky assets, and from finite state spaces to general state spaces.Moreover, we show that, when tradable financial assets are independent of mortality, a locally risk-minimizing hedging strategy for most claims in the combined financial and mortality market (such as those arising from equity-indexed annuities) may be expressed as the product of two simpler locally risk-minimizing hedging strategies: one for a purely financial claim, the other for a traditional (i.e. non-equity-linked) life-insurance claim.Finally, we also show, under general assumptions, that the minimal measure for the combined market is the product of the minimal measure for the financial market and the physical measure for the mortality.     

2D transient filtration model for aluminum

A two-dimensional, transient mathematical model representing the behavior of a deep-bed filter was developed. The flow and mass fraction equations are solved using CFX™ commercial code. The rate equation representing the inclusion deposition and re-entrainment is incorporated into a model as a source term of the mass fraction equation. The resistance of the bed is calculated using the pressure drop calculated by the Ergun equation. The model takes into account all the major physical processes occurring during filtration. For each time step, the model calculates the inclusion concentrations remaining in the liquid and deposited on the filter media. It updates the bed porosity and bed particle size as the inclusions deposit. The model can use either an average inclusion size or a discrete inclusion size distribution. It is also possible to assign different densities to different inclusion sizes if an inclusion distribution is used.     

小波域中的维纳滤波在综合脉冲星时算法中的应用

脉冲星自转非常稳定，可用作时间标准. 然而由单脉冲星定义的脉冲星时受多种噪声源的影响，其频率稳定度还不够好，因此可采取对多颗脉冲星定义的脉冲星时进行综合的方法来削弱各噪声源的影响，以提高脉冲星时的稳定度. 不同的脉冲星有着各自不同的自转频率，在不同频率段所受噪声的影响也不同，应用小波分析的方法对脉冲星时做综合，可以兼顾脉冲星时的长期与短期稳定度，在不同的频率范围取不同的权值以达到更好的结果；脉冲星的计时残差是由计时参考的原子时的误差和脉冲星计时误差两部分引起的，用维纳滤波的方法可以将两者分开，并主要以消除掉参考钟误差后的残差为计时残差实现对脉冲星计时的综合. 在这两种方法的基础上，提出一种基于小波域中的维纳滤波方法，利用小波独有的特性和维纳滤波最小误差估计的优点，更有效地消除噪声对脉冲星时的影响. 实验结果表明，该方法可以有效降低脉冲星计时残差中的噪声影响.     

Efficient protocol for isolation and purification of different soyasaponins from soy hypocotyls

Soyasaponins are naturally occurring triterpenoid glycosides associated with many biological activities. The aim of the present study was to develop an effective method for isolation and purification of differently glycosylated, acetylated, and 2,3‐dihydro‐2,5‐dihydroxy‐6‐methyl‐4H‐pyran‐4‐one (DDMP)‐conjugated soyasaponins from soy hypocotyls. Both gel filtration using Sephadex LH‐20 chromatography (Amersham Pharmacia Biotech AB; elution phase: methanol, flow rate: 3.0 mL/min, sample loading: 60 mg) and high‐speed countercurrent chromatography (stationary phase: n‐butanol–acetic acid (5.0%, v/v), mobile phase: water flow rate: 3.0 mL/min, sample loading: 100 mg) could effectively fractionate isoflavones and soyasaponins from the crude extract with yield of soyasaponin complexes 20.5 mg and 22.3 mg, respectively. After fractionation, the soyasaponin complexes could be purified further using preparative HPLC to separate individuals. A total of nine soyasaponins, triacetyl soyasaponin Ab (yield 1.55%, HPLC purity >98%), Aa (2.68%, >99%), Ab (18.53%, >98%), Ae (0.85%, >98%), Ba (0.63%, >91%), Af (1.12%, >85%), Bb (3.45%, >98%) and Be (0.59%, >76.8%) were obtained. DDMP‐conjugated groups, αg (2.06%, >85%), βg (7.59%, >85%), and γg (0.29%, >85%) that were very labile even in mild conditions, were also collected. The method described here can be used as an effective protocol to separate different soyasaponins occurring in the original sample.