FIGURE 3.

Electron beam–induced structural damages and radical reaction. (A) Broken disulfide bond in PsbO of PII at high-dose (left) and the disulfide bond recovered in PsbO of PII at the low-dose from single-particle averaging cryo-EM 3D reconstruction. Reproduced with permission (Kato et al., 2021). (B) Hypothetical scheme for radical reaction in the radiolysis damage. A radical reaction is initiated when an active site of disulfide bond is converted into radicals under the electron beam. The formation of radicals is a reversible reaction, in which the radicals can react with each other to recover the original biomolecule with a reaction rate constant of k _-1. Increasing k _-1 can inhibit the radiation damage effectively. However, if the radical in region A reacts with different radicals in other regions, the formation of a new reaction product is generally irreversible. The permanent damage in the biomolecule usually misleads the subsequent 3D reconstruction and reduces the structural resolution. Reproduced with permission (Kato et al., 2021).