Structure determination of macromolecular complexes by cryo-electron microscopy in vitro and in situ

Three-dimensional (3-D) cryo-electron microscopy (EM) comprises three different branches: single particle analysis (SPA), cryo-electron tomography (CET), and electron crystallography. In this introduction into 3-D cryo-EM we first summarize the principle of imaging frozen-hydrated specimens by a transmission electron microscope (TEM) three-dimensionally before giving an insight into state-of-the-art strategies for automated data acquisition. For SPA and CET, we then review the respective methodologies and some selected applications highlighting the potential of both techniques, and in less detail we summarize electron crystallography. Finally, we give an account of the rapidly developing methods for model building using cryo-EM maps.