Danev Radostin, Iijima Hirofumi, Matsuzaki Mizuki, Motoki Sohei
Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, Tokyo 113-0033, Japan.
JEOL Ltd, 1-2 Musashino 3-Chome, Akishima, Tokyo 196-8558, Japan.
IUCrJ. 2020 Apr 25;7(Pt 3):566-574. doi: 10.1107/S205225252000408X. eCollection 2020 May 1.
Current data collection strategies in electron cryo-microscopy (cryo-EM) record multiframe movies with static optical settings. This limits the number of adjustable parameters that can be used to optimize the experiment. Here, a method for fast and accurate defocus (FADE) modulation during movie acquisition is proposed. It uses the objective lens aperture as an electrostatic pole that locally modifies the electron beam potential. The beam potential variation is converted to defocus change by the typically undesired chromatic aberration of the objective lens. The simplicity, electrostatic principle and low electrical impedance of the device allow fast switching speeds that will enable per-frame defocus modulation of cryo-EM movies. Researchers will be able to define custom defocus 'recipes' and tailor the experiment for optimal information extraction from the sample. The FADE method could help to convert the microscope into a more dynamic and flexible optical platform that delivers better performance in cryo-EM single-particle analysis and electron cryo-tomography.
目前电子冷冻显微镜（cryo-EM）中的数据采集策略是在静态光学设置下记录多帧电影。这限制了可用于优化实验的可调参数数量。在此，提出了一种在电影采集期间进行快速准确散焦（FADE）调制的方法。它使用物镜光阑作为静电极，局部改变电子束电位。通过物镜通常不需要的色差，束电位变化被转换为散焦变化。该装置的简单性、静电原理和低电阻抗允许快速切换速度，这将实现冷冻电镜电影的逐帧散焦调制。研究人员将能够定义自定义散焦“配方”，并为从样品中提取最佳信息量身定制实验。FADE方法有助于将显微镜转变为一个更具动态性和灵活性的光学平台，在冷冻电镜单颗粒分析和电子冷冻断层扫描中提供更好的性能。
