JEOL CRYO ARM™ achieves top resolution
The field of single particle structure analysis (SPA) by cryo-electron microscopy reached new highs with the publication of a 1.19Å structure of apo-ferritin by Maki-Yonekura et al. obtained using a JEOL CRYO ARM™ 300 model 33001. This electron cryo-microscope was specifically designed for highly automated workflows capable of the unattended acquisition thousands of images of vitrified specimens. Workflow support of the JEOL CRYO ARM™ is available for SPA, batch tomography and microED. The specimen used in the study, apo-ferritin, is a conveniently available benchmark protein used for determining the performance of these highly automated cryo microscopes. In instances where a single chain version is used, 24-fold non-crystallographic averaging can be applied, which vastly improves the signal-to-noise in cryo-EM images.
Fig. 1: Atlas composed of 5x5 pieces of a frozen-hydrated sample imaged at 80x (A). Same grid, but now imaged at 300x showing 4 grid squares that reveal the subtle variation in ice thickness across grid squares (B). Single grid square of the same grid imaged at 800x. All the holes of this sample are filled with thin ice (C).
SPA workflows rely on atlases or maps of the specimen, which allow stage navigation to be used in targeting regions/holes of interest (Fig. 1). Maps taken at successive higher mags allow for precise targeting of holes in the support film using a combination of stage shift and deflector-based shift.
A total of 7900 movies were acquired on a K3 camera at 0.5Å/pixel yielding a total of 2,000,000 particles that were subjected to processing in Relion-3.1. The final map was computed at 1.19Å resolution (Fig. 2). The data was deposited in the EMDB under accession number EMD-35984.
Fig. 2: Apo-ferritin at 1.19Å resolution.
References
- S. Maki-Yonekura, K. Kawakami, K. Takaba, T. Hamaguchi and K. Yonekura (2023), Comm. Chemistry 6, 98