Cryo-electron microscopy (cryo-EM) is a powerful technique for structural biology, but obtaining optimal grids for data collection is challenging. Cryo-EM samples are vitrified in their native solution on grids with a holey carbon support film. Protein molecules in vitreous ice suspended in the holes of the support film are then imaged. The ice layer must be thick enough to preserve the protein structure and thin enough to obtain the best signal-to-noise ratio. Controlling ice thickness is one of the main challenges for cryo-EM.
Researchers at IBS and CEA have proposed the use of a graphene membrane as a solution to this problem. Graphene membranes can be as thin as an atomic layer, and are virtually transparent to electrons. Their excellent mechanical properties make them robust support films, and their high thermal and electrical conductivity protects sensitive protein samples from irradiation damage. Nevertheless, the intrinsic hydrophobicity of graphene hinders its use with biological samples.
This work shows that the wetting properties of graphene can be controlled by plasma treatment. High-resolution imaging and Raman spectroscopy correlate structural and chemical changes at the atomic level with the hydrophilicity of graphene induced by the plasma treatment. A uniform layer of ice with thickness better controlled than that of suspended ice can thus be obtained upon vitrification of protein samples, facilitating the use of graphene as a support film for high-resolution cryo-EM studies.
Precision defect integrated graphene as reliable support membrane for high-resolution cryo-transmission electron microscopy. Sharma K, López-Sánchez U, Nury H, Schoehn G, Darnault C, Breyton C, Petit-Etienne C, Vergnaud C, Ling WL, Cunge G, Okuno H. Carbon 230 (2024) ; 119625.
Contact : Wai Li Ling (IBS/Methods and Electron Microscopy Group)