FIGURE 3.

Proximity-driven fluorescent signal generation approaches. (A) Proximity ligation assay (PLA). Single-stranded oligonucleotides are conjugated to antibody of proteins. Membrane proximity serves to template the hybridization of circularization oligonucleotides, which is then joined by ligation into a circular DNA molecule and followed by amplification of the signal by rolling-circle amplification (RCA). (B) Fluorescence resonance energy transfer (FRET). The photon energy transfers from excited donor to acceptor since the accessible proximity. (C) Bimolecular fluorescence complementation (BiFC). Accessible proximity made GFP1-10 and GFP11 remodel into a mature fluorescent protein. (D) Dimerization-dependent fluorescent proteins (ddFP). Two GFP monomer (ddGFP-A and ddGFP-B) with weak signal form a dimer with fluorescent strong signal since the accessible proximity.