Comparison of near-infrared iRFPs engineered from bacterial phytochromes with several far-red FPs of the GFP-like family as probes for deep-tissue imaging.

aDefined as a product of extinction coefficient and quantum yield. The molecular brightness values are from [19] for five iRFPs, [10] for mNeptune, [11] for E2-Crimson and [13] for eqFP650 and eqFP670.bData are from [19]. The signal-to-background ratios were measured for equal amounts of purified FPs imaged in a planar epifluorescence mode on an IVIS Spectrum instrument (PerkinElmer, Waltham, MA) inside a XFM-2 fluorescent phantom mouse (PerkinElmer) at the indicated depths from the mouse surface using the optimal filter channels for each FP.Comparison of near-infrared iRFPs engineered from bacterial phytochromes with several far-red FPs of the GFP-like family as probes for deep-tissue imaging.