Fig. 4.

To enable cryo-EM SPA of small target proteins of interest (center vignette), the characteristics of the protein can guide choice of strategy for protein size-augmentation. A target binding (left) or a target fusion (right) strategy can be employed, each having multiple variants that together cover a wide range of small protein targets. Boxes in dashed blue lines are additional suggestions. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)