Features & Solutions



Protein & Cell labeling


FAST is a versatile, user-friendly, real-time fluorescent reporting system for various protein and cell labeling applications.

You are interested in

Labeling a protein of interest without perturbing its function?

Monitoring protein expression in real-time?

Adjusting the level of labeling on demand?

Labeling proteins at the cell-surface?

Compatible techniques




How can fast help you?

  • FAST is a small purely monomeric protein, of only 14 kDa. Its small size and minimal genetic footprint (375 bp) minimize the risk of perturbation linked to the use of genetic tags.
  • FAST can be genetically fused at the N- or C-termini of any protein of interest, or inserted within a protein of interest using a circularly permuted variant.
  • FAST binds non-covalently TFFluorogens, fluorogenic synthetic dyes that are dark in water and fluoresce only when bound to FAST, allowing specific detection of FAST.
  • FAST provide strong fluorescence immediately upon addition of TFFluorogens even in fully anaerobic conditions
  • As TFFluorogen binds FAST non-covalently, labeling is non-permanent and can be easily reversed by washing TFFluorogen away.
  • The level of labeling can be controlled by adjusting the concentrations of TFFluorogens.

Other key features:

  • TFFluorogens come in a variety of colors and in permeant and non-permeant versions for intracellular and cell-surface labeling. For intracellular labeling: TFCoral (λem 600 nm), TFCitrus (λem 560 nm), TFAmber (λem 558 nm), TFLime (λem 540 nm); for cell-surface labeling: TFAmber NP (λem 559 nm).

recent papers about this application

A small fluorescence-activating and absorption-shifting tag for tunable protein imaging in vivo

Published in Proc. Natl. Acad. Sci. (USA) 113 (3), 497-502 (2016)

In this seminal paper, Pr. A. Gautier and L. Jullien introduce FAST (Fluorescence-Activating and absorption-Shifting Tag)...

…as a small monomeric protein tag enabling to fluorescently label proteins in a reversible and specific manner through the reversible binding and activation of a cell-permeant and non-toxic fluorogenic ligand. FAST is as bright as common fluorescent proteins, exhibits good photostability and allows the efficient labeling of proteins in various organelles and hosts.

Dynamic multi-color labeling in living cells

Published in Chem. Sci. 8, 5598-5605 (2017)

In this paper, Pr. A. Gautier and L. Jullien report a collection of fluorogens enabling tuning of the fluorescence color of FAST ...

…from green-yellow to orange and red. Beyond allowing the multicolor imaging of FAST-tagged proteins in live cells, these fluorogens enable dynamic color switching because of FAST’s reversible labeling. This unprecedented behavior allows for selective detection of FAST-tagged proteins in cells expressing both green and red fluorescent species through two-color cross-correlation, opening up exciting prospects to overcome spectral crowding and push the frontiers of multiplexed imaging.

Improved chemical-genetic fluorescent markers for protein imaging in living cells

Published in Biochemistry 57, 5648-5653 (2018)

In this paper, Pr. A. Gautier uses rational design to modify the FAST binding pocket for improved fluorescence performances with four different fluorogens...

The introduction of a single mutation results in improvements in both quantum yield and dissociation constant with nearly all fluorogens tested. Our improved FAST (iFAST) allowed the generation of a tandem iFAST (td-iFAST) that forms green and red fluorescent reporters 1.6-fold and 2-fold brighter than EGFP and mCherry, respectively, while having a comparable size.

Fluorogenic probing of membrane protein trafficking

Published in Bioconj. Chem. 29, 1823-1828 (2018)

In this paper, Pr. A. Gautier presents an efficient strategy for the rapid and selective fluorescent labeling of membrane proteins based on FAST...

This approach allows the study of protein trafficking at the plasma membrane with various fluorometric techniques, and opens exciting prospects for the high-throughput screening of small molecules able to restore disease-related trafficking defects.

Other Applications

Labeling in anaeroby

Detecting protein-protein interactions

Protein & cell labeling

One tag, many colors

Reversible labeling, Silent Tag

A toolkit for sensing

The Twinkle Factory

We are a French biotech company that provides ground breaking fluorescent chemical-genetic tools for labelling and imaging



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