SmURFP

[1][2][3] Native α-allophycocyanin requires an exogenous protein, known as a lyase, to attach the chromophore, phycocyanobilin.

[6] The extinction coefficient (180,000 M−1 cm−1) of smURFP is extremely large and has a modest quantum yield (0.18), which makes it comparable biophysical brightness to eGFP and ~2-fold brighter than most red or far-red fluorescent proteins derived from coral.

smURFP nanoparticles of ~10-14 nm diameter can be synthesized in an oil and water emulsion and remain fluorescent.

[13] Free smURFP, purified protein and not genetically encoded, can be encapsulated into viruses and used for non-invasive, fluorescence imaging of biodistribution in living mice.

Researchers showed purified smURFP has a limit of detection of 0.4 nM for biliverdin in human serum.

[18] Tandem dimer smURFP (TDsmURFP) was used as an exogenous fluorescent marker to label the seven-transmembrane receptor Smoothened (SMO).

TDsmURFP was purified from E. coli and attached to SMO by sortase-mediated conjugation for fluorescence-activated cell sorting (FACS).

The smURFP-tag accepts a biliverdin substrate modified on a carboxylate with a polyethylene glycol (PEG) linker to the cargo molecule.

Unlike the Halo-, SNAP-, and CLIP-tags that use the substrate to only covalently attach the cargo molecule, biliverdin is fluorogenic, and fluorescence is turned "on" with covalent attachment to the smURFP-tag to allow far-red fluorescence tracking of cargo molecule in living cells.

Biliverdin modification on a single carboxylate creates a neutral molecule that passes the outer and nuclear membrane of mammalian cells.

[21] Despite showing comparable biophysical brightness to eGFP when purified protein was normalized, this was not seen in living cells.

Add 1-5 μM biliverdin dimethyl ester in media or buffer containing 10% fetal bovine serum (FBS).

A rationally designed red fluorescent protein, stagRFP, allows for easier creation of FRET sensors.

The new sensor allowed for simultaneous visualization of three kinases, Src, Akt, ERK, in a single cell.

Note, these fusions are fragments that contain a nuclear localization signal and ubiquitination sites for degradation, but are not functional proteins.

Fluorescent proteins visualize the cell cycle progression. IFP2.0-hGem(1/110) fluorescence is shown in green and highlights the S/G 2 /M phases. smURFP-hCdtI(30/120) fluorescence is shown in red and highlights the G 0 /G 1 phases.
Image shows E. coli expressing smURFP, pelleting of E. coli , removal of media, E. coli lysis, smURFP binding to NiNTA, smURFP elution, and buffer exchange.
The small Ultra-Red Fluorescent Protein (smURFP) is a self-labeling protein. The substrate is fluorogenic, fluoresces when attached, and quenches fluorescent cargo. The smURFP-tag [ 20 ] has novel properties for tool development.
smURFP was genetically fused to human, lamin B1 to show the nuclear envelope with fluorescence. Localization of the Lamin B1 protein changes during different phases of the cell cycle.
smURFP expressed in neuronal culture does not show aggregation in lysosomes, which was seen with the fluorescent protein, mCherry .
Far Red & Near Infrared FUCCI visualizes the birth of a multinucleated cell, which is common in many cancer cells.
smURFP (light-blue) expressed in E. coli .