椭圆偏振术在生物医学研究中的应用

椭圆偏振术是一种新兴的用于研究生物分子固相表面吸附以及吸附分子间相互作用的表面分析技术。其最大优点在于测量过程不破坏被测体系;而且灵敏度高,可反映接近原子尺寸的变化;又能原位、实时跟踪检测表面膜的变化情况。就椭偏术在生物医学研究的若干重要应用进行综述。     

A蛋白定向固定抗体用于椭偏光学生物传感器免疫检测

椭偏光学生物传感器是在椭偏光学显微成像技术的基础上发展的一项生物传感技术。它能够直接观测固体表面上的生物分子面密度,毋需任何标记辅助,适合发展成为一种无标记免疫检测技术。研究了在硅片表面上通过A蛋白定向固定抗体分子用于椭偏光学生物传感器免疫检测的可能性。实验结果表明,通过A蛋白固定抗体得到的抗体膜层的均一性和固定量的重复性能够保证椭偏光学生物传感器免疫检测结果的质量。通过A蛋白定向固定的抗体的抗原结合位点趋向一致,显著提高了抗体与抗原结合的能力。此外,通过蛋白A固定的免疫球蛋白G分子能够结合更多的多克隆抗体分子说明通过A蛋白固定的蛋白质分子能够较好地保持其空间构象。     

生物被膜在病原细菌与植物识别中的作用

生物被膜是微生物附着在生物或非生物表面所形成的一种三维结构,细胞被其自身所产生的胞外聚合物所包围,生物被膜的形成被认为是微生物应对生物和非生物胁迫时所产生的一种自我防御机制。众多微生物能够在植物叶、维管束和根等组织中生长,并在植物不同组织表面附着形成生物被膜,病原细菌的生物被膜随植物内部环境动态变化是其有效发挥致病作用的关键,研究植物病原细菌生物被膜调控机制是认识植物-病原菌互作的重要方面。文中将系统地介绍植物病原细菌生物被膜特征、组成成分、分子调控机制及最新研究进展。     

亲和素蛋白与含有生物素的支撑平面膜之间相互作用的研究

生物功能分子的二维有序化组装是分子工程学的重要内容,本文通过构建有生物素受体的人工模型膜,对亲和素与生物这一具有极强亲和力的系统之间的特异性相互作用的某些制约因素进行了探讨,应用ＬＢ膜技术结合激光椭圆偏振术和表面等离激元谱技术,较深入地研究了蛋白质与脂单层膜发发的非特异性吸附,特异性结合以及结合的侧向空间位阻效应,实验结果表明,膜表面电荷对非特异性吸附的速率有很大的影响,而对最终的蛋白质附量影响不     

肌动蛋白的原子力显微镜研究

原子力显微镜 (AFM )是一种能够在生理条件下对生物大分子、活细胞表面以及细胞膜下结构进行在体或离体研究的强有力的新型工具 ,具有原子级的成像分辨率和纳牛顿级的力测定功能。目前原子力显微镜已被广泛地应用于生物大分子、超分子体系的结构解析、动力学过程观察 ,分子力学研究及细胞功能鉴定。原子力显微镜能够通过尖锐探针扫描待测样品表面 ,收集被测样品表面地貌坐标数据从而对单分子或细胞进行成像或操作 ,并能通过移动探针、记录探针与样品之间的作用力 ,对生物大分子 (蛋白质、核酸和多糖等 )的结构力学特性进行分析以获取分子构象、功能及其相互关系的有用信息。肌动蛋白是一种细胞内普遍存在 ,具有广泛、复杂生理功能的重要蛋白质 ,原子力显微镜的各项功能已广泛地用于肌动蛋白结构、功能及动力学研究。通过综述原子力显微镜在肌动蛋白研究中的应用 ,阐明了原子力显微镜在现代生命科学研究中的重要意义及巨大应用前景。     

研发动态

中国科学院生物芯片研制最新进展两则中国科学院力学研究所国家微重力实验室靳刚课题组成功研制出“蛋白质芯片生物传感器系统”及其实用化样机。该研究将多种蛋白质活性微列阵、生物分子特异结合性,与高分辨率椭偏光学成像技术相结合,提供了     

保持培养细胞原位、原形的超薄切片制备法

本文介绍先用环氧树脂Epon812包埋剂制成丘状膜,再在膜上培养细胞,直接将膜与细胞一起包埋,制备超薄切片。此种方法不仅能克服以往培养细胞需要离心成团,容易造成细胞破碎、变形的缺点;还能避免琼脂预包埋法悬浮细胞造成的抗原封闭;并能得到为数较多的连续超薄切片。它操作简便,较好地保持了培养细胞生长的原来位置及原有形状,为培养细胞进行免疫电镜的操作和提高制备培养细胞超薄切片的数量和质量提供了一种有效的途径。     

亲和素蛋白与含有生物素的支撑平面膜之间相互作用的研究

生物功能分子的二维有序化组装是分子工程学的重要内容。本文通过构建有生物素受体的人工模型膜,对亲和素与生物素这一具有极强亲和力的系统之间的特异性相互作用的某些制约因素进行了探讨．应用ＬＢ膜技术结合激先椭圆偏振术和表面等离激元谱技术,较深入地研究了蛋白质与脂单层膜发生的非特异性吸附,特异性结合以及结合的侧向空间位阻效应．实验结果表明,膜表面电荷对非特异性吸附的速率有很大的影响,而对最终的蛋白吸附量影响不大;非特异性的吸附可以通过二阶阳离子的脱附而去除;受体蛋白质与配体间的特异性结合受到侧向空间位阻效应的制约．     

偏肺病毒G蛋白:一个多变蛋白的多重角色

偏肺病毒包括人偏肺病毒和禽偏肺病毒,是感染人和禽的一种重要病原。G蛋白是偏肺病毒粒子表面的一种糖蛋白,属II型跨膜蛋白。不同种偏肺病毒G蛋白的大小和同源性差异巨大,发挥的生物学功能也显著不同,如在病毒的吸附过程、病毒介导的细胞融合、对病毒在体内外的复制能力影响以及免疫保护作用都有很大不同。同时,偏肺病毒G蛋白在免疫抑制和免疫逃避中也起着重要作用。目前国内开展的相关研究较少,本文对偏肺病毒G蛋白的最新研究成果和进展进行了综述和讨论,并对未来的相关研究进行了展望。     

SPR生物传感器及其应用进展

基于表面等离子体共振 (SPR)技术的光学生物传感器是进行生物分子相互作用分析的一种先进手段。与传统的超速离心、荧光法等相比 ,它具有实时检测、无需标记、耗样最少等特点 ,在药物筛选、临床诊断、食物及环境监控和膜生物学等领域中的新兴应用日益扩大 ,并且已成为生命科学和制药研究的一种标准的生物物理学工具。综述了近几年国际上生物传感器的应用进展情况 ,并简要展望了该技术的发展和应用前景     

应用椭偏光学显微成像对IL-6与其受体的相互应用的初步观察

白细胞介素 6 (ＩＬ 6 )是一种具有复杂生物功能的细胞因子 ,可由多种淋巴类和非淋巴类细胞产生。它对机体多种组织及细胞均有不同程度的作用[1～ 3 ] 。近年来发现 ,临床上免疫异常性疾病 ,如发热、淋巴结肿大、血沉增快、急性期蛋白增高、高γ球蛋白血症、自身抗体阳性等症状都与ＩＬ 6的异常表达密切相关。ＩＬ 6的生物活性是通过细胞膜表面特异性受体介导的[4] 。研究ＩＬ 6与其受体的相互作用对于揭示某些疾病的发病机制 ,监测疾病进程以及指导临床治疗等均具有重要意义。用于研究ＩＬ 6与其受体相互作用的方法主要有ＩＬ 6依赖株细胞…     

Functionalized fluorescent core-shell nanoparticles used as a fluorescent labels in fluoroimmunoassay for IL-6

Nanoparticle labels conjugated with biomolecules are used in a variety of different assay applications. In this paper, a sensitive fluoroimmunoassay for recombinant human interleukin-6 (IL-6) with the functionalized Rubpy-encapsulated fluorescent core-shell silica nanoparticles labeling technique has been proposed. IL-6 was measured based on the specific interaction between captured IL-6 antigen and functionalized fluorescent core-shell nanoparticles-labeled anti-IL-6 monoclonal antibody. The calibration graph for IL-6 was linear over the range 20-1250 pg ml(-1) with a detection limit of 7 pg ml(-1) (3 sigma). The regression equation of the working curve is I(F)=7.665+32.499[IL-6] (ng ml(-1)) (r=0.9980). The relative standard deviation (R.S.D.) for 11 parallel measurements of 78 pg ml(-1) IL-6 was 3.2%. Furthermore, the application of fluorescence microscopy imaging in the study of the antibody labeling and sandwich fluoroimmunoassay with the functionalized fluorescent core-shell silica nanoparticles was also explored. This proposed method has the advantage of showing the specificity of immunoassay and sensitivity of fluorescent nanoparticle labels technology. The results demonstrate that the method offers potential advantages of sensitivity, simplicity and reproducibility for the determination of IL-6, and is applicable to the determination of IL-6 in serum samples and enabling fluorescence microscopy imaging for the determination of IL-6.     

重组人骨形态发生蛋白-2抗体的制备及纯化

骨形态发生蛋白-2是骨科研究领域的重要生物蛋白。用重组人骨形态发生蛋白-2(rhBMP₂)与BSA连接成复合物作为免疫原,免疫家兔制备出多克隆抗血清。分别用免疫沉淀法和Sepharose4B-BSA反向免疫亲和吸附法去除抗血清中载体BSA抗体。用盐析法和蛋白层析法纯化出抗rhBMP₂抗体。研究发现,家兔产生高效价抗体的最佳时间为14-16周,从rhBMP₂抗体的特异性、相对纯度及回收率综合分析,免疫沉淀法去除BSA抗体优于反相亲和吸附法。     

Polyhydroxyalkanoate chip for the specific immobilization of recombinant proteins and its applications in immunodiagnostics

In this study, a novel strategy was developed for the highly selective immobilization of proteins, using the polyhydroxyalkanoate (PHA) depolymerase substrate binding domain (SBD) as an active binding domain. In order to determine the appropriacy of this method for immunodiagnostic assays, the single-chain antibody (ScFv) against the hepatitis B virus (HBV) preS2 surface protein and the severe acute respiratory syndrome coronavirus (SARS-CoV) envelope protein (SCVe) were fused to the SBD, then directly immobilized on PHA-coated slides via microspotting. The fluorescence-labeled HBV antigen and the antibody against SCVe were then utilized to examine specific interactions on the PHA-coated surfaces. Fluorescence signals were detected only at the spotted positions, thereby indicating a high degree of affinity and selectivity for their corresponding antigens/antibodies. Furthermore, we detected small amounts of ScFv-SBD (2.7 ng/mL) and SCVe-SBD fusion proteins (0.6 ng/mL). Therefore, this microarray platform technology, using PHA and SBD, appears generally appropriate for immunodiagnosis, with no special requirements with regard to synthetic or chemical modification of the biomolecules or the solid surface.     

Side-by-Side Comparison of Commonly Used Biomolecules That Differ in Size and Affinity on Tumor Uptake and Internalization

The ability to use a systemically injected agent to image tumor is influenced by tumor characteristics such as permeability and vascularity, and the size, shape, and affinity of the imaging agent. In this study, six different imaging biomolecules, with or without specificity to tumor, were examined for tumor uptake and internalization at the whole body, ex-vivo tissue, and cellular levels: antibodies, antibody fragments (Fab), serum albumin, and streptavidin. The time of peak tumor uptake was dependent solely on the size of molecules, suggesting that molecular size is the major factor that influences tumor uptake by its effect on systemic clearance and diffusion into tumor. Affinity to tumor antigen failed to augment tumor uptake of Fab above non-specific accumulation, which suggests that Fab fragments of typical monoclonal antibodies may fall below an affinity threshold for use as molecular imaging agents. Despite abundant localization into the tumor, albumin and streptavidin were not found on cell surface or inside cells. By comparing biomolecules differing in size and affinity, our study highlights that while pharmacokinetics are a dominant factor in tumor uptake for biomolecules, affinity to tumor antigen is required for tumor binding and internalization.     

Photopatterning of antibodies on biosensors

The immobilization of biomolecules on surfaces in defined micropatterns has become increasingly important for the development of new diagnostic devices and high-throughput genetic and drug screening protocols. We describe the synthesis and testing of thiol-reactive, photoactivatable linkers that will permit laser micropatterning or photolithographic patterning of surfaces. In these linkers, a benzophenone photophore is tethered through a variable-length poly(ethylene glycol) hydrophilic spacer to a maleimide group. Spacers containing one to five ethylene glycol units were examined. Antibodies were photoimmobilized on polystyrene waveguides and the resulting biosensors were used for fluorescence immunoassays. The spacer with five ethylene glycol units optimally decreased the steric interactions among large molecules (antibodies and antigens) and increased binding capacity and response rate of the biosensor. Two different sandwich assay protocols were examined. In the first, the antigen and fluorescently labeled second antibody were added sequentially to the biosensor ("stepwise"). In the second, the antigen and antibody were premixed before injection into the biosensor ("premixed"). The stepwise protocol gave a significantly higher response than that of the premixed protocol. Although the premixed protocol is more convenient, the stepwise protocol provides enhanced sensitivity.     

Antibody recognition imaging by force microscopy.

We have developed a method that combines dynamic force microscopy with the simultaneous molecular recognition of an antigen by an antibody, during imaging. A magnetically oscillated atomic force microscopy tip carrying a tethered antibody was scanned over a surface to which lysozyme was bound. By oscillating the probe at an amplitude of only a few nanometers, the antibody was kept in close proximity to the surface, allowing fast and efficient antigen recognition and gentle interaction between tip and sample. Antigenic sites were evident from reduction of the oscillation amplitude, as a result of antibody-antigen recognition during the lateral scan. Lysozyme molecules bound to the surface were recognized by the antibody on the scanning tip with a few nanometers lateral resolution. In principle, any ligand can be tethered to the tip; thus, this technique could potentially be used for nanometer-scale epitope mapping of biomolecules and localizing receptor sites during biological processes.     

Light-induced immobilisation of biomolecules as an attractive alternative to microdroplet dispensing-based arraying technologies

The present work shows how UV 'light-induced molecular immobilisation' (LIMI) of biomolecules onto thiol reactive surfaces can be used to make biosensors, without the need for traditional microdispensing technologies. Using 'LIMI,' arrays of biomolecules can be created with a high degree of reproducibility. This technology can be used to circumvent the need for often expensive nano/microdispensing technologies. The ultimate size of the immobilised spots is defined by the focal area of the UV beam, which for a diffraction-limited beam can be less than 1 microm in diameter. LIMI has the added benefit that the immobilised molecules will be spatially oriented and covalently bound to the surface. The activity of the sensor molecules is retained. Antibody sensor arrays made using LIMI demonstrated successful antigen binding. In addition, the pattern of immobilised molecules on the surface is not restricted to conventional array formats. The ultimate consequence of the LIMI is that it is possible to write complex protein patterns using bitmaps at high resolution onto substrates. Thus, LIMI of biomolecules provides a new technological platform for biomolecular immobilisation and the potential for replacing present microdispensing arraying technologies.     

The labeled antigen method of immunoenzymatic staining.

A two stage immunohistological technique (the "labeled antigen" procedure) has been assessed for the detection of a variety of human and animal cytoplasmic constituents in tissue sections. In this method specific antiserum is followed by antigen complexed to horseradish peroxidase or to alkaline phosphatase. The primary antibody acts bivalently, linking the labeled antigen to antigen in the tissue section. The major advantage of this technique is that nonantigen specific antibody in the primary antiserum cannot cause nonspecific staining since it has no affinity for the antigen:enzyme complex. Consequently the specificity of the reaction is assured, background staining is minimized and the total staining time (from wax section to mounted slide) can be reduced to as little as 30 min. Further advantages include the possibility of labeling Ig allotypes and the high efficiency of enzyme utilization. Covalent human IgG:horseradish peroxidase complexes can also be used in a triple sandwich in conjunction with human anti-viral or autoimmune antibodies.     

Red blood cells imaging and antigen-antibody interaction measurement

In the present study the atomic force microscope (AFM) was used to image the surface morphology of red blood cells (RBC) for the first time. The AFM yielded very reproducible images without appreciable modifications of the sample surfaces. In addition to this topographical imaging, we have developed an experimental approach to measure the binding strength between antibody (anti-A), and the RBC antigen A, when reversible bonds between specific molecules such as antigen and antibody mediate the adhesion. The experimental results suggest that the procedure established here may be used for specific antibody detection. This study has also enhanced our understanding under physiological conditions of molecular interaction in particular antigen-antibody.