Photoactivatable fluorescent proteins

- Light-induced high-contrast photoconversion
- Easy detection by flow cytometry or fluorescence microscopy
- No cofactors, substrates, or chemical staining required
- Suitability for long-term tracking of cellular events

Photoactivatable fluorescent proteins (PAFPs) represent a unique tool for monitoring cellular events. PAFPs change spectral properties in response to irradiation with specific light. In recent years PAFPs have been utilized for the development of novel methods for the optical labeling and tracking living cells, organelles, and intracellular molecules in a spatio-temporal manner. PAFPs became indispensible tools for super-resolution imaging techniques. Moreover, PAFPs opened new possibilities to study cell physiology, in particular, they allow careful determination of protein half-life.

Available proteins

CHARACTERISTIC	PS-CFP2	KFP-Red	PA-TagRFP
* Brightness is a product of extinction coefficient and quantum yield, divided by 1000. Ext.coeff. – extinction coefficient.
Fluorescence color	cyan   /   green	NO   /   red	NO   /   red
Excitation max (nm)	400   /   490	580   /   580	-   /   562
Emission max (nm)	468   /   511	600   /   600	-   /   595
Quantum yield	0.20   /   0.23	<0.001   /   0.07	nd   /   0.38
Ext. coeff. (M-1cm-1)	43 000   /   47 000	123 000   /   59 000	nd   /   66 000
Brightness*	8.6   /   10.8	0   /   4.1	0   /   25.1
Activating light	UV-violet (e.g. 405 nm)	green (530-560 nm)	UV-violet (e.g. 390-420 nm)
Calculated contrast, fold	up to 2000	35-70	~540
Structure	monomer	tetramer	monomer
Cell toxicity	not observed	not observed	not observed
Aggregation	no	no	no
Maturation rate at 37°C	fast	medium	fast
Molecular weight (kDa)	27	26	27

Discontinued proteins:

Dendra2