Genetically engineered avidins and streptavidins

Chicken avidin and bacterial streptavidin, (strept)avidin, are proteins widely utilized in a number of applications in life science, ranging from purification and labeling techniques to diagnostics, and from targeted drug delivery to nanotechnology. (Strept)avidin-biotin technology relies on the extremely tight and specific affinity between (strept)avidin and biotin (dissociation constant, K_d≈10⁻¹⁴–10⁻¹⁶ M). (Strept)avidins are also exceptionally stable proteins. To study their ligand binding and stability characteristics, the two proteins have been extensively modified both chemically and genetically. There are excellent accounts of this technology and chemically modified (strept)avidins, but no comprehensive reviews exist concerning genetically engineered (strept)avidins. To fill this gap, we here go through the genetically engineered (strept)avidins, summarizing how these constructs were designed and how they have improved our understanding of the structural and functional characteristics of these proteins, and the benefits they have provided for (strept)avidin-biotin technology. Received 22 June 2006; received after revision 1 August 2006; accepted 21 September 2006     

Multilayers Assembly of DNA Probe for Biosensor

IntroductionThere are many kinds of biosensors for detectingthe interactions of protein-protein,protein-DNAand enzyme-substrates.Surface plasmon resonance(SPR) biosensor is one of the importantdetectingtechniques.The analytical system is based on asensor chip that uses SPR to monitor theinteraction of biomolecules on a sensor chip.SPRis an optical phenomenon,which is sensitive tochanges in the optical properties of the mediumclose to a metal surface[1 ] .This optical techniquemeasures the…     

高效差分表面等离激元共振传感器

为了减小现有的表面等离激元共振传感器的系统漂移和溶液体效应引起的误差,利用四元光电探测器,发展了一种差分SPR传感器,通过对信号的差分运算消除这些误差.测试结果表明, 该仪器有2个突出的优点:具有10-5(°)或10-8 RIU的高角向分辨率;能同时消除系统漂移和溶液体介电常数效应引起的误差,10min内漂移小于7×10-5(°).利用这种传感器,测量浓度为 0.55nmol/L的抗生物素, 得到很好的响应特性,证明该装置可用于生物分子的检测.     

应用纳米与分子探针技术对IgG抗原水平的检测

人们研究并逐步认识了纳米金与DNA等相互作用的特性和条件,并对以纳米金为基础发展起来的生物条码技术进行了更加深入的研究与应用。基于纳米金的生物条码及其相关技术研究与应用日益广泛,并不断有创新,本研究应用纳米技术并结合分子探针技术对低浓度的抗原水平进行检测。该生物条码技术常被用于检测某些蛋白、核酸、细胞或细胞因子的水平,并由此形成了不同于PCR、ELISA但仍具有高灵敏度特性的检测方法。通过磁性微球标记单抗以捕获、富集待测抗原,修饰多抗与亲和素的纳米金并结合分子信标探针起到信号扩增的作用。通过二硫键（-S—S-）分子信标探针茎部3’端的碱基T连接-生物素分子。待测抗原可将磁球与纳米金系统进行连接,然后应用二硫苏糖醇（DTT）将连接于纳米金上的MB切割下来,并与其环部完全互补配对的靶序列杂交后测定荧光强度。荧光强度与待测抗原水平（含量）相关。