Extended Data Fig. 4: Single-molecule counting level imaging of AuNPs direct-synthesized on individual tag fusion proteins.
From: Genetically encoded tags for direct synthesis of EM-visible gold nanoparticles in cells
a, c, e, g, EM images of negative stained MBP-2MT, MBP-MTn, MBP-MTa and MBP-2AFP, showing single molecules (~7 nm in sizes) marked with 8 nm x 8 nm red boxes. b, d, f, h, EM images of MBP-2MT, MBP-MTn, MBP-MTa, and MBP-2AFP molecules underwent ANSM-based AuNP synthesis, followed by 2 % UA negative staining; the 8 nm x 8 nm red boxes marked out these proteins forming AuNPs on the tags in 1:1 ratio. The 8 nm x 8 nm white boxes marked out those proteins without visible AuNPs, which might be caused by insufficient exposure to gold thiolate sources due to protein aggregations (for example, the purified MBP-MTa seems unstable and tends to form aggregates). To avoid multiple AuNPs aggregations with the standard 2-ME/D-P AuNP synthesis protocol (Fig. 2), here we a TCEP/D-P AuNP synthesis protocol used for (b, d, f, h) (Methods). Representative images for (a-h) were selected from n = 4 independent experiments with similar results.
