Exploring chemical properties through 3D ED and cryo-EM

Using the diffraction mode of transmission electron microscopy (TEM), diffraction patterns can be obtained from small three-dimensional (3D) crystals of sample molecules due to the significant atomic cross-sections for electrons. By rotating the sample stage in a TEM, discrete diffraction spots within the 3D reciprocal space are swept, enabling structural determination. This method, known as 3D electron diffraction (3D ED) or Microcrystal electron diffraction (MicroED), has become a useful TEM technique for studying 3D structures, alongside single-particle cryogenic electron microscopy (cryo-EM) and tomography.

With 3D ED, various samples, including proteins, polypeptides, and organic compounds – whether present as crystals in aqueous solutions, organic solvents, or as dried powders – can be studied. We have contributed to the development of this technique, which now allows rapid processing of large datasets collected via AI control, making structural determination more efficient. My group is particularly interested in the possibility of Coulomb potential information explored by using this technique. We will present our approach and recent findings, covering both the limitations and potential of 3D ED in comparison to serial crystallography with X-ray free-electron lasers (XFELs) and single-particle cryo-EM. A recent example demonstrates that 3D electron diffraction (ED) elucidates complex multiple conformations of a novel organic compound, which other techniques, including XFEL, have not resolved.