Microsecond melting and revitrification of cryo samples: protein structure and beam‐induced motion

• Published in: Acta crystallographica. Section D, Biological crystallography. Vol. 78; no. 7; pp. 883 - 889
• Main Authors: Harder, Oliver F., Voss, Jonathan M., Olshin, Pavel K., Drabbels, Marcel, Lorenz, Ulrich J.
• Format: Journal Article
• Language: English
• Published: 5 Abbey Square, Chester, Cheshire CH1 2HU, England International Union of Crystallography 01-07-2022; Wiley Subscription Services, Inc
• Subjects: Apoferritin; beam‐induced motion; Cowpeas; Cryoelectron Microscopy - methods; Electron microscopy; Freezing; Laser beams; laser melting; Melting; microsecond time‐resolved cryo‐EM; Motion; Protein structure; Proteins; Research Papers; revitrification; single‐particle reconstructions; Spatial discrimination; Spatial resolution; Vitrification; laser melting; revitrification; microsecond time-resolved cryo-EM; single-particle reconstructions; beam-induced motion
• ISSN: 2059-7983; 0907-4449; 2059-7983; 1399-0047
• DOI: 10.1107/S205979832200554X

A novel approach to time‐resolved cryo‐electron microscopy (cryo‐EM) has recently been introduced that involves melting a cryo sample with a laser beam to allow protein dynamics to briefly occur in the liquid, before trapping the particles in their transient configurations by rapidly revitrifying the sample. With a time resolution of just a few microseconds, this approach is notably fast enough to study the domain motions that are typically associated with the activity of proteins but which have previously remained inaccessible. Here, crucial details are added to the characterization of the method. It is shown that single‐particle reconstructions of apoferritin and Cowpea chlorotic mottle virus from revitrified samples are indistinguishable from those from conventional samples, demonstrating that melting and revitrification leaves the particles intact and that they do not undergo structural changes within the spatial resolution afforded by the instrument. How rapid revitrification affects the properties of the ice is also characterized, showing that revitrified samples exhibit comparable amounts of beam‐induced motion. The results pave the way for microsecond time‐resolved studies of the conformational dynamics of proteins and open up new avenues to study the vitrification process and to address beam‐induced specimen movement.
Microsecond melting and revitrification of cryo samples preserves the structure of embedded particles. The beam‐induced motion of revitrified samples is comparable to that of conventional cryo samples.