Template-free, polymerase-free DNA polymerization

Experimental Guidelines to Image Transient Single-Molecule Events Using Graphene Liquid Cell Electron Microscopy

In quest of the holy grail to "see" how individual molecules interact in liquid environments, single-molecule imaging methods now include liquid-phase electron microscopy, whose resolution can be nanometers in space and several frames per second in time using an ordinary electron microscope that is routinely available to many researchers. However, with the current state of the art, protocols that sound similar to those described in the literature lead to outcomes that can differ. The key challenge is to achieve sample contrast under a safe electron dose within a frame rate adequate to capture the molecular process. Here, we present such examples from different systems─synthetic polymer, lipid assembly, DNA-enzyme─in which we have done this using graphene liquid cells. We describe detailed experimental procedures and share empirical experience for conducting successful experiments, starting from fabrication of a graphene liquid cell, to identification of high-quality liquid pockets from desirable shapes and sizes, to effective searching for target sample pockets under electron microscopy, and to discrimination of sample molecules and molecular processes of interest. These experimental tips can assist others who wish to make use of this method.

DNA-based self-assembly for functional nanomaterials

The unprecedented development of DNA nanotechnology has caused DNA self-assembly to attract close attention in many disciplines. In this research news article, the employment of DNA self-assembly in the fields of materials science and nanotechnology is described. DNA self-assembly can be used to prepare bulk-scale hydrogels and 3D macroscopic crystals with nanoscale internal structures, to induce the crystallization of nanoparticles, to template the fabrication of organic conductive nanomaterials, and to act as drug delivery vehicles for therapeutic agents. The properties and functions are fully tunable because of the designability and specificity of DNA assembly. Moreover, because of the intrinsic dynamics, DNA self-assembly can act as a program switch and can efficiently control stimuli responsiveness. We highlight the power of DNA self-assembly in the preparation and function regulation of materials, aiming to motivate future multidisciplinary and interdisciplinary research. Finally, we describe some of the challenges currently faced by DNA assembly that may affect the functional evolution of such materials, and we provide our insights into the future directions of several DNA self-assembly-based nanomaterials.