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 probes are suitable for stable imaging of protein interactions in living cells and live mice. Proteins for in vivo imaging have emission near or above 650 nm as signals below 650 nm are highly absorbed by hemoglobin and cause undesirable background signals.
Near-infrared fluorescent proteins for in vivo imaging are derived from bacterial phytochrome photoreceptors (BphPs). Spectrally distinct permanently fluorescent iRFP variants have been shown to have high effective brightness and allow for single or multicolor imaging. Photo-activatable iRFPs can be ‘turned on’ by non-phototoxic far-red light and are 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.