Functionalized graphene grids with various charges for single-particle cryo-EM

A major hurdle for single particle cryo-EM in structural determination lies in the specimen preparation impaired by the air-water interface (AWI) and preferential particle-orientation problems. In this work, we develop functionalized graphene grids with various charges via a dediazoniation reaction for cryo-EM specimen preparation. The graphene grids are paraffin-assistant fabricated, which appear with less contaminations compared with those produced by polymer transfer method. By applying onto three different types of macromolecules, we demonstrate that the high-yield charged graphene grids bring macromolecules away from the AWI and enable adjustable particle-orientation distribution for more robust single particle cryo-EM structural determination. Air-water interface and preferential orientation problems are crucial challenges in cryo-EM specimen preparation. Here, the authors utilize graphene-coated EM grids functionalized by salts with various electrostatic properties, successfully overcoming preferred orientation.