Enhancing the Electron Radiation Resistance of Macromolecules in Cryo-TEM Imaging Using Sodium Ascorbate

Electron radiation damage hinders the high-resolution cryogenic transmission electron microscopy (cryo-TEM) imaging of macromolecules. In this work, sodium ascorbate (SA) was used to eliminate reactive oxygen species generated during electron radiation, thereby enhancing the electron radiation resistance of macromolecular samples in cryo-TEM experiments. The effectiveness of SA on protecting sample morphology and structure was investigated for representative types of macromolecular samples, including collagen, cellulose, liposome, and apoferritin, and compared with other radical scavengers. Our findings revealed that SA provided the most effective protection for collagen, increasing its dose limit by more than 40%. Similar effects were observed for cellulose and apoferritin. Importantly, the addition of SA does not change the three-dimensional structure of apoferritin, as confirmed by a 2.2 Å resolution single particle analysis, further indicating the practicality of the method.