Preparation of scFv-immobilized quartz crystal microbalance sensor by PS-tag-mediated solid-phase refolding

The activation of a single-chain Fv antibody on the surface of a quartz crystal microbalance (QCM) sensor chip was investigated in order to develop an economical and sensitive immuno-QCM sensor system for use in clinical diagnosis. On the bare gold surface of a QCM sensor chip, approximately 60nm of hydrophilic polystyrene (phi-PS) thin film that specifically binds the polystyrene-binding peptide (PS-tag) was prepared by spin-coating and O(2)-plasma irradiation. When the adsorption of PS-tag-fused anti-ED-B scFv (scFv-PS) onto the phi-PS surface was directly monitored, the maximum density of scFv-PS attained was 1.56μg/cm(2), 1.6-times higher than that of scFv. The specific antigen-binding activity of scFv-PS after solid-phase refolding increased with the density of immobilized scFv-PS, and, consequently, activity 1.7 times higher than that of scFv was retained. The scFv-PS-immobilized QCM sensor chip rapidly allowed the detection of clear signals for antigen at the range of 0.1-10μg/ml, while no signal was detectable for 10μg/ml BSA as a negative control. The scFv-PS-immobilized QCM sensor developed in the present study will therefore be very useful for the rapid and highly sensitive detection of biomarkers, and should be applicable to clinical diagnosis.     

纤维电荷对阳离子聚电解质吸附性能的影响

以DQP漂白竹浆和麦草浆为原料,以CPAM作为阳离子聚电解质的模型物,以聚电解质滴定技术为研究方法,在测量纤维表面电荷和聚合物电荷密度的基础上,研究CPAM在纤维表面上的吸附量与纤维表面电荷特性的关系.结果发现,在纤维表面电荷一定的情况下聚电解质达到饱和吸附时的吸附量与纤维的表面电荷有很好的对应关系.     

QCM immunosensor with nanoparticle amplification for detection of Escherichia coli O157:H7

A quartz crystal microbalance (QCM) immunosensor was developed and evaluated for detection of Escherichia coli O157:H7. The immunosensor was fabricated by self-assembling of protein A and affinity-purified anti-E. coli O157:H7 antibodies on the gold electrode of an AT-cut piezoelectric quartz crystal. To enhance the sensitivity of the QCM immunosensor, nanoparticle-antibody conjugates, which were prepared using streptavidin-conjugated nanoparticles (145 nm diameter) and biotinylated anti-E. coli antibodies, were used for signal amplification. After the binding of E. coli O157:H7 cells with the antibodies immobilized on the electrode, nanoparticle-antibody conjugates were introduced as mass amplifiers. Compared to the direct detection of E. coli O157:H7, the binding of the nanoparticle conjugates further resulted in a decrease in resonant frequency and an increase in resonant resistance, and the detection sensitivity was improved by five orders of magnitude by lowering the detection limit from 10⁷ to 10² CFU/mL. The sensor specificity and nonspecific adsorption of nanoparticle-antibody conjugates were also investigated.     

The applicability of the GAB model to food water sorption isotherms

Summary  The fitting ability of the GAB equation has been analysed. It has been shown that the GAB model describes well sigmoidal type isotherms when parameters are kept in the following regions: 0.24 7lt; k ≤ 1 and 5.67 ≤ c ≤∞. Outside these regions the isotherm is either no longer sigmoidal or the monolayer capacity is estimated with the error larger than ± 15.5%. Moreover, keeping constants in the above regions fulfils the requirements of the BET model.     

Interaction of cationic starch derivatives and cellulose fibres in the wet end and its correlation to paper strength with a statistical evaluation

The adsorption onto a softwood pulp of cationic modified starches with a degree of substitution (DS) ranging from 0.015 to 0.130 and native potato starch was investigated using a method based on size exclusion chromatography‐multi angle laser light scattering (SEC‐MALLS). This technique provides information about the amount and molecular composition of the adsorbed starch product such as the AP–AM‐ratio, the average MW and molar mass distribution. Factors influencing adsorption, like the electrolyte content in the suspension and the initial starch polysaccharide concentration, were investigated. Furthermore, hand sheets were made and the resulting mechanical paper strength was tested. Results were analysed statistically using analysis of variance. Representative results were discussed in detail. In general, low‐substituted cationic starch (DS 0.030) exhibited a higher degree of adsorption and resulted in high paper strength when there was a low electrolyte content in the starch–pulp‐suspension. However, high amounts of electrolytes impeded electrostatic interaction of the charged groups of the starch polysaccharides and cellulose fibre due to partial screening and therefore strongly limited adsorption. This resulted in lowered mechanical paper strength. The water quality of the suspensions had little impact on the polyelectrolyte adsorption of the highly substituted cationic starch (DS 0.100). However, paper strength was markedly higher in the case of starch adsorption where there was a high ionic content and when both starch polysaccharides–AP and AM– were adsorbed. The initial starch concentration determined starch adsorption both quantitatively and qualitatively and subsequently paper strength as well. The relation between adsorption behaviour and paper strength was discussed, particularly in the case of 6% initial starch concentration. In deionised water (DW), the low‐substituted starch (DS 0.03) adsorbed onto the pulp to a greater extent with an AP–AM‐ratio similar to that of the initial starch. Moreover, this achieved the best strength properties in contrast to 36 dGH, where less starch adsorbed and that being almost exclusively AP. In water with 36 dGH, the highly substituted starch (DS 0.100) with both the AP and AM was absorbed and this resulted in higher paper strength. In contrast, AM was almost exclusively adsorbed in DW. Increasing the initial starch concentration increased the amount adsorbed while subsequently changing the AP–AM‐ratio towards increased AM adsorption and decreased AP adsorption in the case of DS 0.100 in DW. Exclusive adsorption of AM markedly lowered the development of the paper strength.     

Analysis of water binding in starch plasticized films

The water-binding properties of wheat starch films were studied through the determination of water vapour adsorption isotherms at 20 °C. Starch films were obtained by casting after mixing native starch at 95 °C for 15 min with different ratios of plasticizer (glycerol).     

复合凝胶球对水中结晶紫的吸附特性

以海藻酸钠(SA)、玉米秸秆生物炭(BC)、壳聚糖(CTS)为原料制得复合凝胶球(SA/BC/CTS),利用扫描电镜(SEM)和红外光谱(FTIR)初步表征其结构.以结晶紫为吸附对象,考察染料溶液pH、吸附剂质量浓度、吸附时间和染料初始质量浓度对吸附过程的影响.结果 表明:SA/BC/CTS的孔隙率高,官能团丰富;在吸...     

Cry2A蛋白的石英晶体微天平检测

目的：建立检测苏云金芽孢杆菌Cry2A蛋白的石英晶体微天平（quartz crystal microbalance,QCM）传感方法。方法：根据抗原抗体相互作用原理,利用QCM技术,在金片表面修饰抗原所对应的单克隆抗体,对苏云金芽孢杆菌Cry2A蛋白进行检测研究。结果：该方法灵敏度达到1 μg/mL,特异性好、重复性高。结论：该方法有利于为苏云金芽孢杆菌蛋白检测提供新思路,可以应用到实际样品的检测,在农产品转基因检测和进出口检验检疫中具有很好的应用前景。     

The derivation of the GAB adsorption equation from the BDDT adsorption theory

The BET‐like adsorption equation, popularly known as the GAB equation, was derived from the BDDT adsorption equation without changes to the bulk liquid properties of multilayer molecules. Without these changes the third parameter K in the GAB equation cannot be said to measure changes in the bulk liquid properties of the multilayer molecules. Instead K measures the range of application of the GAB equation and differentiates multilayer adsorption, when K > 0.5, from singular layer adsorption, when K ≤ 0.5. The GAB equation, derived from and based on the BDDT theory is argued, in this paper, to provide a greater insight into the mechanism of water adsorption than the same equation derived from and based on the BET theory.     

纳米硅铝酸盐沸石晶体的合成及其对重金属的吸附机制

在Linde F(K)沸石制备过程中引入双特征官能团长链有机物对沸石微观结构进行重构,限制其生长尺寸,合成纳米硅铝酸盐沸石晶体,旨在提高其对重金属的吸附能力.利用XRD、SEM、TEM、XPS等现代分析手段对对合成材料进行表征,研究其对水中重金属的吸附机制.结果表明,合成材料尺寸为200～500 nm,液相比表面积为2...     

电聚合制备三聚氰胺分子印迹QCM传感器薄膜及其表征研究

通过研究得出,在聚合电压U为0~1.6V、聚合段数为22、模板三聚氰胺(MEL)浓度为4mmol/L、单体甲基丙烯酸(MAA)浓度为10mmol/L、成膜剂邻苯二胺(o-PD)浓度为18mmol/L条件下,以pH 8.0的BR缓冲液作为溶剂和电解液,用电聚合方法,直接在石英晶体微天平(QCM)传感器电极上修饰的分子印迹薄膜,其对目标分子MEL具有良好的频率表征效果,频移值为59Hz.通过相同3个修饰电极的频率表征变化来看,电极对目标分子的识别表征极不稳定.这与手动进样方式、环境较大噪声和电极本身差异密切相关,难以建立对目标分子的标准曲线(r=0.966)实现准确定量分析.     

碱性吸附剂稳定性及其在油脂脱酸中吸附平衡作用

分别探讨自制碱性吸附剂酸稳定性和热稳定性,并将其应用到油脂脱酸工艺中。试验结果表明,碱性吸附剂在pH<2时不稳定,150℃处理对其脱酸效果有较大影响;其直线型吸附等温线方程为:Xe/q=0.0046Xe+0.0177,饱和吸附容量达217.39 mg/g。     

Detection of a complementary couple of single-stranded DNAs by use of a quartz crystal device for determination of bacteria

Preliminary experiments were carried out for the DNA detection targeting a complementary couple of single-stranded DNAs originating from Nitrobacter winogradskyi. The target DNAs were detected successfully with a quartz crystal unit bearing probe DNAs, based on the oscillation frequency decrease due to hybridization of the probe and target DNAs.     

植物抗冻蛋白分离纯化方法的研究进展

为植物抗冻蛋白是一类具有热滞活性的蛋白质,它能抑制冰晶的生长和重结晶。因其特殊的结构和功能,植物抗冻蛋白对延长冷冻食品的贮藏期和提高产品质量具有积极意义。从复杂提取液中高效分离纯化出抗冻蛋白已成为当前热点和难点问题,作者介绍了近年来植物抗冻蛋白分离纯化方法的基本原理和研究进展,主要有传统层析分离方法、SDS-PAGE电泳、冰特异吸附分离法和浊点萃取法,展望了抗冻蛋白分离纯化方法的未来发展方向。