RNA Nanostructure Molecular Imaging.

Atomic force and transmission electron microscopies (AFM/TEM) are powerful tools to analyze RNA-based nanostructures. While cryo-TEM analysis allows the determination of near-atomic resolution structures of large RNA complexes, this chapter intends to present how RNA nanostructures can be analyzed at room temperature on surfaces. Indeed, TEM and AFM analyses permit the conformation of a large population of individual molecular structures to be observed, providing a statistical basis for the variability of these nanostructures within the population. Nevertheless, if double-stranded DNA molecular imaging has been described extensively, only a few investigations of single-stranded DNA and RNA filaments have been conducted so far. Indeed, technique for spreading and adsorption of ss-molecules on AFM surfaces or TEM grids is a crucial step to avoid disturbing RNA conformation on the surface. In this chapter, we present a specific method to analyze RNA assemblies and RNA-protein complexes for molecular microscopies.