Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, 2629HZ, The Netherlands.
Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.
Small. 2017 Aug;13(31). doi: 10.1002/smll.201700876. Epub 2017 Jun 16.
While graphene may appear to be the ultimate support membrane for transmission electron microscopy (TEM) imaging of DNA nanostructures, very little is known if it poses an advantage over conventional carbon supports in terms of resolution and contrast. Microscopic investigations are carried out on DNA origami nanoplates that are supported onto freestanding graphene, using advanced TEM techniques, including a new dark-field technique that is recently developed in our lab. TEM images of stained and unstained DNA origami are presented with high contrast on both graphene and amorphous carbon membranes. On graphene, the images of the origami plates show severe unwanted distortions, where the rectangular shape of the nanoplates is significantly distorted. From a number of comparative control experiments, it is demonstrated that neither staining agents, nor screening ions, nor the level of electron-beam irradiation cause this distortion. Instead, it is suggested that origami nanoplates are distorted due to hydrophobic interaction of the DNA bases with graphene upon adsorption of the DNA origami nanoplates.
虽然石墨烯似乎是用于 DNA 纳米结构透射电子显微镜 (TEM) 成像的最佳支撑膜，但关于它在分辨率和对比度方面是否优于传统碳衬底，人们知之甚少。我们使用先进的 TEM 技术（包括我们实验室最近开发的一种新的暗场技术）对自由支撑在石墨烯上的 DNA 折纸纳米板进行了微观研究。对染色和未染色的 DNA 折纸进行 TEM 成像，在石墨烯和非晶态碳膜上均呈现出高对比度的图像。在石墨烯上，折纸板的图像显示出严重的不需要的失真，其中纳米板的矩形形状明显失真。通过一系列比较对照实验，证明既不是染色剂，也不是屏蔽离子，也不是电子束照射的程度导致这种失真。相反，有人认为，由于 DNA 折纸纳米板在吸附 DNA 折纸纳米板时与石墨烯之间存在疏水性相互作用，导致 origami 纳米板发生变形。
