3.7.3 RESI
RESI is the first SRN technique to boast a subnanometer resolution (Reinhardt et al., 2023). The principle of RESI is based on sequential DNA-PAINT imaging with fluorophores of different colours and re-application of the concept of localization to super-resolution data. RESI gets close to the resolution of cryo-electron microscopy, but the true capabilities of this technique have yet to be thoroughly tested.
An important aspect of recent developments in SRN is that the size of the fluorescent marker and its localisation have become highly critical to obtaining accurate results. FPs and self-labelling systems, such as SNAP-tag or HaloTag, have become unsatisfactorily large for the desired spatial resolution. Distantly located fluorescent labels do not accurately report the localisation of the protein of interest. Therefore, genetic code expansion with unnatural amino acids, ligand-directed labelling, and the utilisation of subnanometer tags (Arsic et al., 2022; Mihaila et al., 2022) will likely become the mainstream for the future development and application of SRN techniques.