A team lead by Prof. Arnaud Gautier discloses frFAST for far-red labeling in Angew. Chem. Int. Ed. 2020. The team gathers researchers from Sorbonne University, and Collège de France and ENS of PSL Research University.
The high demand for RFP, and furthermore far-red fluorescent proteins, has emerged from the need for new colors. Indeed the growing use of optical biosensors and optogenetic tools obstruct the spectral window available for biological imaging. Moreover, far-red fluorescent proteins allow imaging deeper in tissues. Indeed, autofluorescence, light scattering and absorbance by endogenous molecules is reduced in the far-red region.
This paper discloses a far-red system, frFAST and HPAR-3OM, engineered from the original FAST tag and HBR-based fluorogens. HPAR-3OM is a membrane-permeant fluorogenic ligand which selectively binds frFAST-tagged proteins. It works in solution, in living cells or in fixed cells. HPAR-3OM is almost non-fluorescent when free in solution. But it strongly fluoresces when bound to frFAST. Gautier designed HPAR-3OM together with a variant of FAST, frFAST, specifically for far-red labeling. frFAST and HPAR-3OM allow for imaging proteins in mammalian cells, but also in zebrafish embryo/larvae and chicken embryo. Gautier eventually developed a rapid and reversible split-frFAST to image protein-protein interactions in live cells.