Programming conventional electron microscopes for solving ultrahigh-resolution structures of small and macro-molecules.

Microcrystal electron diffraction (MicroED) is becoming a powerful tool in determining the crystal structures of biological macromolecules and small organic compounds. However, wide applications of this technique are still limited by the special requirement for radiation-tolerated movie-mode camera and the lacking of automated data collection methods. Herein, we develop a stage-camera synchronization scheme to minimize the hardware requirements and enable the use of the conventional electron cryo-microscope with single-frame CCD camera, which ensures not only the acquisition of ultrahigh-resolution diffraction data but also low cost in practice. This method renders the structure determination of both peptide and small organic compounds at ultrahigh resolution up to ~0.60 Å with unambiguous assignment of nearly all hydrogen atoms. The present work provides a widely applicable solution for routine structure determination of MicroED, and demonstrates the capability of the low-end 120kV microscope with a CCD camera in solving ultra-high resolution structures of both organic compound and biological macromolecules.