Construction of Scanning Tunneling Microscope for the Study of Interacting Biological Molecualr Systems and their Preparation

我们已经开发了一种扫描隧道显微镜(STM)，它可以在清洁和特定的条件下对生物材料进行工作。随着扫描隧道显微镜在表面科学领域的巨大成功，人们对其在生物医学领域的应用进行了许多尝试，但收效甚微。困难在于厚的有机和生物样品的导电性很差，而且来自不同研究小组的结果往往重复性很差。第一个问题是目标材料的物理性质所固有的，但第二个问题往往是在不太明确的环境下进行的测量，例如在湿度不明确的大气条件下进行的测量。我们在这里开发的装置在一个大的腔室中有一个STM扫描单元，在那里不仅可以进行STM操作，而且可以在新制备的衬底表面上涂抹湿生物样品。这样，样品被空气中的杂质污染的可能性很小。使用这个仪器和新的软件，我们已经在干净和明确的条件下对DNA、蛋白质、噬菌体、病毒和细胞膜进行了成像。厚样品，如噬菌体和病毒，必须包覆一层薄的金属以供扫描电子显微镜观察，如果这种金属涂层的厚度足够薄，我们就可以根据表面形貌的信息来识别一些结构细节。我们现在能够将完成的仪器完全应用于生物表面的地形研究。

WE have developed a scanning tunneling microscope (STM) that works on biological materials under clean and defined conditions. Following the great success of STM is the field of surface science, many attempts have been made to test its use in bio-medical field with limited success. The difficulty lies in both the poor electrical conductivity of thick organic and biological samples and often poorly reproducible results from various research groups. The first problem is inherent to the physical nature of the target material but the second is often the measurement done under less well defined environment such as atmospheric condition with unspecified humidity. The apparatus we developed here has an STM scanning unit in a large chamber where not only the STM operation but also application of wet biological samples on a freshly prepared substrate surface can be done. In this way, there is little possibility that the sample is contaminated with impurity in air. Using this apparatus and new software, we have imaged DNA, proteins, bacteriophages, viruses and cell membranes under clean and well defined conditions. Thick samples such as phages and viruses must be coated with thin layr of metal to be observed by STM.If the thickness of such metal coating is thin enough, we could identify some structural details with the information on the surface topography. We are now in the position to fully apply the completed apparatus to the topographical studies of biological surfaces.