Experimental Validation of the Predicted Properties of a Multiphasic Buffer System Applied to Polyacrylamide Gel Electrophoresis

Abstract

The properties of a buffer system predicted by T. M. Jovin's theory of multiphasic (discontinuous) buffer systems have been tested experimentally both in free solution and in polyacrylamide gels. The most widely applied multiphasic buffer system, viz., the Tris-glycine system of Ornstein and Davis was used for this purpose. The properties of this system were computed on the basis of the Jovin theory. The pH, specific conductance, and boundary displacement were measured in the buffers corresponding to the original and the operative buffers of both the stacking (upper) gel and the separation (lower) gel in polyacrylamide gel electrophoresis. Values of pH and specific conductance in the absence of gels were found to be in reasonable agreement with theory. In polyacrylamide gels, after removal of residual reactants of the polymerization reaction by equilibration with the appropriate buffer, there was good agreement between observed and predicted values of pH and boundary displacement. However, the observed values for specific conductance were lower than predicted. The effects of pre-electrophoresis and of gel concentration on pH, conductance, and boundary displacement were also studied.

A new method has been developed for formation of stable pH gradients in polyacrylamide gel electrophoresis using multiphasic buffer systems. A concentration and pH gradient in the upper (stacking) gel as formed results in a pH gradient in the operative stacking gel (after passage of the stack). This pH gradient is stable for at least 8 h in the system investigated, and may be applicable to protein fractionation.     

鼠肝高尔基体双向凝胶电泳的建立

目的分离纯化鼠肝高尔基体,初步建立一套相对完善、分辨率和重复性均较高的高尔基体双向凝胶电泳技术。方法应用蔗糖密度梯度超离心法分离纯化高尔基体,通过电镜观察和标志酶分析鉴定其形态及纯度,双向凝胶电泳分离高尔基体蛋白质,用PDQuest8.0软件分析电泳图谱。结果电镜观察显示大部分为高尔基体,纯化高尔基体标志酶TPP酶比活力提高了120倍,得到了分辨率和重复性均较好的双向凝胶电泳图谱。结论已成功建立了鼠肝高尔基体双向凝胶电泳技术。     

在高浓度尿素的存在下采用制备型电泳体系进行聚丙烯酰胺凝胶电泳分离腐植酸成分

采用制备型电泳体系在高浓度的尿素存在下进行聚丙烯酰胺凝胶电泳分离水溶性腐植酸中的不同成分。在聚丙烯酰胺凝胶电泳中,根据水溶性腐植酸中深色成分分子大小的不同能够将它们彼此分离开来,同时还可以通过酸沉淀的方法将这些深色物质重新回收。水溶性腐植酸中大部分的荧光物质分子尺寸都很小,这使得它们可以溶于酸,并且被酸溶解的荧光物质可以通过吸附在DAX-8树脂上而重新获得。但是,水溶性腐植酸中的非荧光物质则会在电泳过程中丢失。而那些被认为是小分子的荧光物质则会通过氢键的断裂和7 M尿素的疏水作用得到分离。漫反射傅里叶变换红外光谱的测量结果表明腐植酸中不同成分的化学性质是不同的。而实验结果表明在高浓度尿素存在下聚丙烯酰胺凝胶电泳是分离和收集水溶性腐植酸中各组分的一种很有用的方法。     

钴钼系CO宽温耐硫变换催化剂硫化条件的研究

考察了硫化剂种类、硫化温度以及硫化原料气中水含量等不同硫化条件对两类典型的钴钼系CO宽温耐硫变换催化剂（Co-Mo—K／MgAl2O4＋Al2O3型和Co—Mo／MgAl2O4型）性能的影响。结果表明：采用H2S作硫化剂能提高催化剂低温和中温活性;尽可能在高温下进行硫化;硫化介质中水蒸气含量对沉积一沉淀型催化剂活性的影响相对小于对浸渍型催化剂的影响。     

宽温域高阻尼橡胶材料研究进展

文中介绍了宽温域高阻尼橡胶材料的作用机理、性能指标及其发展概况。阻尼橡胶的主要性能指标为损耗因子tanδ、玻璃化转变温度Tg、阻尼峰半高宽温度△0．7；影响阻尼橡胶性能的最主要因素是橡胶的分子结构，其次为填充体系、硫化体系。该文最后介绍了阻尼橡胶的改性方法：共混法、互穿网络法、填充法等。     

Design of PG-Surfactants Bearing Polyacrylamide Polymer Chain to Solubilize Membrane Proteins in a Surfactant-Free Buffer

The development of techniques capable of using membrane proteins in a surfactant-free aqueous buffer is an attractive research area, and it should be elucidated for various membrane protein studies. To this end, we examined a method using new solubilization surfactants that do not detach from membrane protein surfaces once bound. The designed solubilization surfactants, DKDKC₁₂K-PA_n (n = 5, 7, and 18), consist of two parts: one is the lipopeptide-based solubilization surfactant part, DKDKC₁₂K, fand the other is the covalently connected linear polyacrylamide (PA) chain with different M_w values of 5, 7, or 18 kDa. Intermolecular interactions between the PA chains in DKDKC₁₂K-PA_n concentrated on the surfaces of membrane proteins via amphiphilic binding of the DKDKC₁₂K part to the integral membrane domain was observed. Therefore, DKDKC₁₂K-PA_n (n = 5, 7, and 18) could maintain a bound state even after removal of the unbound by ultrafiltration or gel-filtration chromatography. We used photosystem I (PSI) from Thermosynecoccus vulcanus as a representative to assess the impacts of new surfactants on the solubilized membrane protein structure and functions. Based on the maintenance of unique photophysical properties of PSI, we evaluated the ability of DKDKC₁₂K-PA_n (n = 5, 7, and 18) as a new solubilization surfactant.     

宽温域耐R134a氢化丁腈橡胶胶料的性能研究

采用机械共混法制备氢化丁腈橡胶(HNBR)胶料,研究助交联剂TAIC、陶土及马来酸酐接枝液体聚丁二烯(MA-LB)对HNBR胶料物理性能和耐R134a性能的影响。结果表明:随着助交联剂TAIC用量的增大,胶料的交联密度增大,物理性能、耐热性能和耐R134a性能提高;陶土N85能够降低R134a的穿透性,使得HNBR胶料具有更好的耐R134a性能;当MA-LB用量为6份时,胶料具有良好的综合物理性能和耐R134a性能。O形圈在宽温域环境(-55℃×72 h和150℃×72 h下循环两次)的密封试验结果表明,压缩率大于25%能够保证O形圈在R134a中密封性能的可靠性。     

The RhoGEF Trio: A Protein with a Wide Range of Functions in the Vascular Endothelium

Many cellular processes are controlled by small GTPases, which can be activated by guanine nucleotide exchange factors (GEFs). The RhoGEF Trio contains two GEF domains that differentially activate the small GTPases such as Rac1/RhoG and RhoA. These small RhoGTPases are mainly involved in the remodeling of the actin cytoskeleton. In the endothelium, they regulate junctional stabilization and play a crucial role in angiogenesis and endothelial barrier integrity. Multiple extracellular signals originating from different vascular processes can influence the activity of Trio and thereby the regulation of the forementioned small GTPases and actin cytoskeleton. This review elucidates how various signals regulate Trio in a distinct manner, resulting in different functional outcomes that are crucial for endothelial cell function in response to inflammation.     

大温度区间氢的高压吸附等温线模型

氢在活性炭上的吸附等温线模型是储氢和分离氢气等工程项目的热力学和工程计算基础。Ｌａｇｍｕｉｒ１Ｆｒｅｕｎｄｌｉｃｈ,Ｖｉｒｉａｌ和Ｄｕｂｉｎｉｎ－Ａｓｔａｋｈｏｖ方程是用来描述气／固体系吸附等温线最常见的模型。但昆它们在大温度范围的适用性从来没有检验过。本文采用７７－２９８Ｋ,０－７ＭＰａ范围内氢在活性炭上的吸／脱附数据,分别检验了上述四方程式对于实验数据的拟合程度,并以各实验温度一的标准偏差和整     

A Nitrogen-Laser Photolysis Apparatus in the Nanosecond Range: The Excited Singlet-Singlet Absorption Spectrum of Coronene

The application of a low energy pulsed nitrogen laser as a fast excitation source in photochemistry is described. The experimental problems concerning detection of transients by absorption spectroscopy are discussed. The instrument is applied to the measurement of the absorption spectrum curve of coronene in its lowest excited singlet state.     

Test Rig for Hybrid System Emulation: New Real‐Time Transient Model Validated in a Wide Operative Range

This paper reports an entirely new simulation tool for a hybrid system emulator facility built by the Thermochemical Power Group (TPG) at the University of Genoa, Italy. This new software was developed with the following targets: real‐time performance, good stability level and high calculation reliability. In details, to obtain real‐time performance a new approach based on 0‐D technique was chosen also for components usually analysed with 1‐D or 2‐D tools (e.g. the recuperator). These are essential key aspects to operate it in hardware‐in‐the‐loop mode or to evaluate predictive results for long transient operations. This work was based on collaboration between the University of Manchester, UK and the University of Genoa, Italy. The activity was carried out with a test rig composed of the following technology: a microturbine package able to produce up to 100 kWe and modified for external connections, external pipes designed for several purposes (by‐pass, measurement or bleed), and a high temperature modular vessel necessary to emulate the dimension of an SOFC stack. The real‐time transient model of this facility was developed inside the Matlab‐Simulink environment with the following modelling approach: a library of components allows to reach a high level of flexibility and an user‐friendly approach. This model includes the machine control system as an essential device to analyse further layouts (new components in the rig) and hardware‐in‐the‐loop operations. The experimental data collected in the laboratory by TPG were used to validate the simulation tool. The results calculated with the model were satisfactory compared with experimental data considering both steady‐state and transient operations. The most important innovative aspects of this work are related to this wide validation range (not only small power steps, but the whole operative range was considered) obtaining real‐time performance and considering microturbine conditions different from standard operations (additional pressure and temperature losses and unusual thermal capacitance). The modelling simplified approach used for such a complex system is an important innovative aspect, because usually the model reliability performance is obtained with more complex (and not real‐time) tools. This work is based on an innovative modelling approach based on 0‐D tools able to operate in real‐time mode (as necessary for hardware‐in‐the‐loop tests) with an accuracy level comparable with more complex and more time consuming software. This validated tool is an important base for future calculations to study innovative hybrid system layouts. For instance, TPG is planning to analyse the option of increasing fuel cell pressure and performance with a booster system (e.g. a turbocharger).     

Comparison of Three Particle Number Concentration Calibration Standards Through Calibration of a Single CPC in a Wide Particle Size Range

We carried out a set of experiments to compare three particle number concentration standards (NCSs) by calibrating the same condensation particle counter (CPC) unit (Model 3772, TSI Inc., Shoreview, MN, USA). The standards were, in the order of operation size range, the primary NCS of the National Institute of Advanced Industrial Science and Technology (AIST, Japan), the Single Charged Aerosol Reference (SCAR) (Finland), and the Inkjet Aerosol Generator (IAG) of AIST. The results obtained with the 3 standards were found to agree at all overlapping particle sizes within the uncertainty limits. The relative expanded uncertainties varied between 0.6% and 2.6%, depending on the size and standard, while the overall agreement between the standards was within 0.5%. The observed consistency of the results is an important step toward establishing internationally coherent particle NCSs. As a result, the CPC 3772 was successfully calibrated in a particularly wide size range, approximately from 10 nm to 10 μm. The results indicate that the CPC can be considered as a practical tool for calibrating particle number concentration up to 1 μm. In general, the particle number concentration can be measured up to 2.5 μm without a significant decrease of the detection efficiency. By attaching an appropriate size-classifying inlet, the CPC could be used even for measuring the total number concentration for particles smaller than 2.5 μm, in parallel with the PM_2.5 mass measurement. Above this particle diameter, the detection efficiency gradually decreased and reached 50% at about 10 μm.

Copyright 2012 American Association for Aerosol Research     

常温高压下气体在液体中溶解度测定装置的研制

建立了一套常温高压下气体在液体中溶解度的测定装置,压力可达10 MPa。装置具有以下特点:采用逆流双循环流程;气、液二相都由电磁泵循环;平衡釜上装有两组圆形视镜便于控制液面;在流动的管路中取样;死体积小;采用液体为恒温介质,恒温槽温度控制良好;耐腐蚀等。从二个方面对装置的可靠性进行了检验。对产生误差的因素进行了全面的分析,表明实验结果的精度在1％以内。当文献上查不到所测体系的常压溶解度x_o时,可根据本文提出的方法从高压实验数据回归出     

Simultaneous Records of Methane and Nitrous Oxide Emissions in Rice-Based Cropping Systems under Rainfed Conditions

Rainfed rice (Oryza sativa L.)-based cropping systems are characterized by alternate wetting and drying cycles as monsoonal rains come and go. The potential for accumulation and denitrification of NO₃ ^– is high in these systems as is the production and emission of CH₄ during the monsoon rice season. Simultaneous measurements of CH₄ and N₂O emissions using automated closed chamber methods have been reported in irrigated rice fields but not in rainfed rice systems. In this field study at the International Rice Research Institute, Philippines, simultaneous and continuous measurements of CH₄ and N₂O were made from the 1994 wet season to the 1996 dry season. During the rice-growing seasons, CH₄ fluxes were observed, with the highest emissions being in organic residue-amended plots. Nitrous oxide fluxes, on the other hand, were generally nonexistent, except after fertilization events where low N₂O fluxes were observed. Slow-release N fertilizer further reduced the already low N₂O emissions compared with prilled urea in the first rice season. During the dry seasons, when the field was planted to the upland crops cowpea [Vigna unguiculata (L.) Walp] and wheat (Triticum aestivum L.), positive CH₄ fluxes were low and insignificant except after the imposition of a permanent flood where high CH₄ fluxes appeared. Evidences of CH₄ uptake were apparent in the first dry season, especially in cowpea plots, indicating that rainfed lowland rice soils can act as sink for CH₄ during the upland crop cycle. Large N₂O fluxes were observed shortly after rainfall events due to denitrification of accumulated NO₃ ^–. Cumulative CH₄ and N₂O fluxes observed during this study in rainfed conditions were lower compared with previous studies on irrigated rice fields.     

3D Modeling of the Elastic-Plastic Behavior of Thin Aeronautical Adhesive Films Suited for a Wide Range of Tensile/Compression-Shear Loads

Adhesive bonding is an interesting structural assembling technique for weight saving in modern commercial aircraft, in which the use of composites materials is increasing. In order to meet both optimization and respect of safety conception constraints, the development of accurate numerical strategies is required. Thus, improvement in the experimental characterization and in the design of reliable numerical tools for bonded assemblies is necessary. This paper presents the characterization of the elastic-plastic behaviour of four aeronautical adhesive films, consisting of two epoxy-based resins supported by two types of carrier. The characterization over a wide range of monotonic proportional tensile-shear loads is performed using a modified Arcan test device designed to strongly limit the influence of edge effects. Moreover, to obtain an accurate definition of the initial elastic limit of the adhesives, further experimental tests have been performed using a pressure vessel especially designed to study the influence of the hydrostatic stress. Inverse identification techniques using finite element analysis have been used to identify the material parameters of an elastic-plastic model based on the experimental results (the load-displacement curves). Results underline the potential of such a model to represent the non-linear behaviour of ductile adhesives under tensile/compression-shear proportional monotonic loads.     

Detailed Consideration of Electrical and Dielectric Properties of Au/Ni/n-Si MS Structure in a Wide Frequency Range

Silicon - In the presented study, the electrical and dielectric properties of Au/Ni/n–Si MS structure are examined in detail by performing frequency–dependent admittance spectroscopy...