Protein-Nanoparticle Complex Structure Determination by Cryo-Electron Microscopy.

Methods that allow the study of the structure of proteins in complex with nanomaterials promise to enhance our understanding of how biological molecules interface with inorganic materials. We used single-particle cryo-electron microscopy (cryo-EM) to demonstrate the potential for cryo-EM analysis to reveal structural details of protein-nanoparticle complexes. Two protein-nanomaterial complexes, namely, GroEL bound to platinum nanoparticles (GroEL-PtNP) and ferritin bound to an iron oxide nanoparticle, were used as model samples. For the GroEL-PtNP complex, a final reconstruction was obtained to 3.93 Å, which allowed us to fit the atomic model of GroEL into the resulting map. This sets the stage for future work and improvements on the use of cryo-EM for the study of protein-nanomaterial complexes.