Fluorescent Proteins: In Vivo Imaging

In vivo imaging is a powerful tool used to study individual plasmids or protein-protein interactions in deep-tissue organs and whole mammals. Genetically encoded fluorescent proteins most suitable for stable imaging of protein interactions in living cells and live mice are those with emission near or above 650 nm, as signals below 650 nm are highly absorbed by hemoglobin and cause undesirable background signals.

Many near-infrared fluorescent proteins for in vivo imaging are derived from bacterial phytochrome photoreceptors (BphPs). Spectrally distinct fluorescent iRFP variants have been shown to have high brightness and allow for single or multicolor imaging. Photo-activatable iRFPs can be turned on by non-phototoxic far-red light and can be used for spatially selective imaging of tissues in living animals. Further development of the original iRFP has resulted in a split fluorescence complementation probe used for detecting protein-protein interactions in vitro and in vivo. Learn more about in vivo imaging tools in this blog post.

Far Red

Protein	Excitation/Emission	Brightness	Plasmids
mCardinal	604/659	18	mCardinal plasmids from Chu et al. (2014)
mNeptune	600/650	13.4	pcDNA3-mNeptune-N
E2-Crimson	611/646	28.98	pEF.myc.ER-E2-Crimson

Near-Infrared

Protein	Excitation/Emission	Brightness	Plasmids
iRFP670	643/670	12.7	piRFP670-N1
miRFP670	642/670	12	pmiRFP670-N1
iRFP682	663/682	10.2	piRFP682-N1
iRFP702	673/702	7.6	piRFP702-N1
miRFP703	673/703	8	pmiRFP703-N1
miRFP709	683/709	4	pmiRFP709-N1
iRFP (aka iRFP713)	690/713	6.2	piRFP
iRFP720	702/720	5.8	piRFP720-N1
iSplit	690/713	5.3	pPAS-E and pK-GAFm

Photoactivatable

Protein	Excitation/Emission	Brightness	Plasmids
PAiRFP1	690/717 (after photoactivation)	3.2	pPAiRFP1-N1
PAiRFP2	692/719 (after photoactivation)	3.0	pPAiRFP2-N1