In our postgenomic era, understanding of protein‐protein interactions by characterizing the structure of the corresponding protein complex is becoming increasingly important. An important problem is that many protein complexes are only stable for a few minutes. Dissociation will occur when using the typical, time‐consuming purification methods such as tandem affinity purification and multiple chromatographic separations. Therefore, there is an urgent need for a quick and efficient protein‐complex purification method for 3D structure characterization. The graphene oxide (GO)·streptavidin complex is prepared via a GO·biotin·streptavidin strategy and used for affinity purification. The complex shows a strong biotin recognition capability and an excellent loading capacity. Capturing biotinylated DNA, fluorophores and Au nanoparticles on the GO·streptavidin complexes demonstrates the usefulness of the GO·streptavidin complex as a docking matrix for affinity purification. GO shows a high transparency towards electron beams, making it specifically well suited for direct imaging by electron microscopy. The captured protein complex can be separated via a filtration process or even via on‐grid purification and used directly for single‐particle analysis via cryo‐electron microscopy. Therefore, the purification, sample preparation, and characterization are rolled into one single step.

A novel method is described for preparing single walled carbon nanotube (SWNT)−streptavidin complexes via the biotin−streptavidin recognition. The complex shows stability in 18 days, strong biotin recognition capability, and excellent loading capacity (about 1 streptavidin tetramer per 20 nm of SWNT). Capturing biotinylated DNA, fluorophores, and Au nanoparticles (NPs) on the SWNT−streptavidin complexes demonstrates their usefulness as a docking matrix, for instance for electron microscopy studies, a technique requiring a virtually electron transparent support.