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Red fluorescent protein JRed

- True-red fluorescence
- Proven suitability to create stably transfected cell lines

JRed is a red fluorescent protein obtained by mutagenesis of Anthomedusae jellyfish chromoprotein [Shagin et al., 2004]. JRed fluorescence (excitation/emission maxima are 584 and 610 nm, respectively) can be detected using most popular filter sets.

Main properties

JRed spectra

JRed normalized excitation (thin line) and emission (thick line) spectra.

Download JRed spectra (xls)

* Brightness is a product of extinction coefficient and quantum yield, divided by 1000.
Molecular weight, kDa27
Polypeptide length, aa242
Fluorescence colortrue-red
Excitation maximum, nm584
Emission maximum, nm610
Quantum yield0.20
Extinction coefficient, M-1cm-144 000
Brightness, % of EGFP26
Structureweak dimer
Maturation rate at 37°Cslow
Cell toxicityat certain excitation wavelengths
Main advantagestrue-red fluorescent protein with good compatibility with popular filter sets
Possible limitationsdimer, limited applicability for fusions generation; unsuitable for expression in procaryotes

Recommended filter sets and antibodies

JRed can be recognized using Anti-KillerRed antibody (Cat.# AB961) available from Evrogen.

JRed can be detected using TRITC filter set or similar. Recommended Omega Optical filter sets are QMAX-Red and XF174.

Performance and use

JRed can be expressed in eukaryotic cells; however, it is not appropriate for expression in prokaryotic.

JRed possesses relatively fast photobleaching rate upon arc lamp irradiation. At the same time, it exhibits high photostability when excited by 543 nm laser line in a confocal microscope, with the photobleaching time several times longer compared with DsRed2. JRed could show phototoxicity when bleached.

Mammalian cells transiently transfected with JRed vector give red fluorescence without visible aggregation. Mammalian cells transiently transfected with JRed expression vectors produce bright fluorescence in 24 hours after transfection.

JRed suitability to generate stably transfected cells has been proven by Marinpharm company. Cell lines expressing JRed are commercially available.

Fluorescent microscopy of stably transfected mammalian cells expressing JRed in cytosol.

Images were kindly provided by Dr. Christian Petzelt (Marinpharm).

Despite dimerization capacity, JRed demonstrates successful performance in fusions with subcellular localization signals and many cellular proteins including BH3 interacting domain death agonist (BID), nucleolar protein fibrillarin, dopamin transporter (hDAT). However, we recommend that you use monomeric TagFPs for protein labeling applications.

Fluorescent microscopy of mammalian cells expressing JRed fusions.

Image of stably transfected PtK rat kangaroo cells expressing mitochondria-targeted JRed was kindly provided by Dr. Christian Petzelt (Marinpharm).


  • Shagin DA, Barsova EV, Yanushevich YG, Fradkov AF, Lukyanov KA, Labas YA, Semenova TN, Ugalde JA, Meyers A, Nunez JM, Widder EA, Lukyanov SA, Matz MV. GFP-like proteins as ubiquitous metazoan superfamily: evolution of functional features and structural complexity. Mol Biol Evol. 2004; 21 (5):841-50. / pmid: 14963095
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