Enhancing the\nElectron Radiation Resistance of Macromolecules\nin Cryo-TEM Imaging Using Sodium Ascorbate

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