Summary
A bioRxiv preprint presents SGFP–G, a split-GFP graphene grid that selectively captures GFP11-tagged proteins and lets researchers check enrichment by fluorescence before vitrification. The authors demonstrated the platform with apoferritin and obtained a 2.58 Å cryo-EM reconstruction.
A bioRxiv preprint describes a graphene cryo-electron microscopy grid that uses split green fluorescent protein (split GFP) to selectively capture tagged proteins. The platform, called SGFP–G, also provides a fluorescence-based way to inspect target enrichment and particle distribution before the sample is frozen.
The authors demonstrated the approach with GFP11-tagged apoferritin and report a 2.58 Å cryo-EM reconstruction. They say the grid is designed for low-concentration samples or cell lysates and can reduce the amount of sample needed for high-resolution structural studies.
How the SGFP–G grid works
Cryo-EM samples are placed on a grid and rapidly frozen into vitrified ice before being imaged. The quality of a reconstruction depends in part on whether enough target particles are captured in suitable positions on the grid.
SGFP–G uses graphene as the grid surface and attaches the GFP1–10 fragment of split GFP to it. A target protein carrying the complementary GFP11 tag can then be selectively captured through the interaction between the two GFP fragments. The resulting fluorescent signal allows researchers to examine where the tagged protein has been enriched before vitrification.
The grid architecture places captured proteins away from both the graphene surface and the air–water interface. The authors also introduce a strategy intended to reduce nonspecific protein adsorption, which they say improves selective enrichment of the target protein.
This combines two functions in one grid: molecular recognition to concentrate a chosen protein, and fluorescence imaging to provide a check of capture and distribution before the cryo-EM sample is frozen.
Apoferritin demonstration reached 2.58 Å
For the reported demonstration, the researchers used apoferritin carrying a GFP11 tag. They used fluorescence to guide protein capture and then collected cryo-EM data from the prepared grid. The resulting reconstruction had a reported resolution of 2.58 Å.
That result shows that the affinity-capture strategy can be paired with a high-resolution cryo-EM workflow for at least this tagged protein. It is particularly relevant to structural biology experiments in which the target is available only at low concentration or is present in a more complex sample such as a cell lysate.
The approach does require the target protein to carry the GFP11 tag, so applying it to a new protein would involve a compatible tagging or labelling step. The supplied study summary describes the apoferritin experiment as the platform demonstration; broader performance across proteins and sample types will depend on further testing.
The work is presented as a bioRxiv preprint. The authors also disclose that Hanwen Feng, Zhao Wang and Mingxing Teng are contributors to Baylor College of Medicine provisional patent application BLG 26-061.