Institute of NanoEngineering and Microsystems, National Tsing Hua University, Hsinchu 30034, Taiwan.
IEEE Trans Nanobioscience. 2010 Dec;9(4):289-96. doi: 10.1109/TNB.2010.2070516. Epub 2010 Sep 13.
Fast and efficient detection of Cobra cardiotoxin (CTX) protein molecules on biochip surfaces is an example of application in biotechnology. One potential application of mixed self assembled monolayers (SAMs) as chip surfaces yield different binding affinities of the CTX proteins, a series of studies on the interaction force between CTX proteins and the mixed SAMs surfaces formed from mixtures of two thiols with the same/different chain lengths and/or with the same/different terminal groups will be investigated. In these dual papers, the mixed SAMs of n-alkinethiol SAMs of different chain lengths are chosen as the first examples of this series due to the simple functions of the mixed SAMs surface structure. Thus, the adhesion force measurements of CTX protein molecules on mixed SAMs of n-alkinethiol SAMs of different chain lengths: 1-decanethiol (C9) and 1-hexanethiol (C5) with different mixing ratios are developed and conducted using atomic force microscope (AFM). There are two major tasks in Part I of the dual papers: the development of the AFM measurements providing reliable information, and selection of the surface with highest binding affinity among this mixed SAMs group. Results indicate that the adhesion forces for CTX protein molecules on mixed SAMs with mixing ratio (χ(C9)) of 0.25, 0.5, 0.75 and 1, are 1.26, 1.8, 1.38, and 1.25 folds respectively, compared with the adhesion force of CTX protein molecules on the C5 surface only. Therefore, the SAM surfaces of χ(C9) = 0.5 is the best choice as a biomaterial sensor of this group of mixed SAMs because the strongest binding force and highest efficiency. Effects of the loading force of the AFM operation, the radius of curvature of the AFM tip, and the AFM tip endurance as well as control experiments were examined to ensure the quantitative determination of adhesion force for AFM measurement. The physical mechanism of protein adsorption on SAM surfaces will be studied and analyzed by molecular dynamics (MD) simulations and will be reported in Part II of the dual papers to compensate the limited information on the interaction taking place at atomic level that experiments cannot provide.
在生物芯片表面上快速有效地检测眼镜蛇心脏毒素（CTX）蛋白分子是生物技术应用的一个例子。混合自组装单层（SAM）作为芯片表面的一种潜在应用，会产生 CTX 蛋白不同的结合亲和力，一系列关于 CTX 蛋白与由两种硫醇组成的混合物形成的混合 SAM 表面之间相互作用力的研究将被展开。在这两篇论文中，由于混合 SAM 表面结构的简单功能，选择不同链长的 n-烷硫醇 SAM 的混合 SAM 作为该系列的第一个例子。因此，使用原子力显微镜（AFM）对不同链长的 n-烷硫醇 SAM 的混合 SAM 上 CTX 蛋白分子的粘附力进行了测量：1-癸硫醇（C9）和 1-己硫醇（C5）以不同的混合比例进行测量和实验。在这两篇论文的第一部分有两个主要任务：开发提供可靠信息的 AFM 测量技术，并在这个混合 SAM 组中选择具有最高结合亲和力的表面。结果表明，与仅在 C5 表面上的 CTX 蛋白分子的粘附力相比，在混合 SAM 中具有混合比（χ（C9））为 0.25、0.5、0.75 和 1 的 CTX 蛋白分子的粘附力分别为 1.26、1.8、1.38 和 1.25 倍。因此，作为这个混合 SAM 组的生物材料传感器，χ（C9）= 0.5 的 SAM 表面是最佳选择，因为它具有最强的结合力和最高的效率。研究了 AFM 操作的加载力、AFM 探针的曲率半径以及 AFM 探针的耐久性和对照实验的影响，以确保 AFM 测量中粘附力的定量测定。蛋白质在 SAM 表面上的吸附的物理机制将通过分子动力学（MD）模拟进行研究和分析，并将在这两篇论文的第二部分中进行报告，以弥补实验无法提供的原子水平相互作用的有限信息。
