Upon binding of two proximity probes (usually antibodies conjugated to DNA) to the same target protein complex, the oligonucleotides on the proximity probes are brought close together. These antibody-conjugated oligonucleotides hybridize to two connector oligonucleotides that are ligated to form a circular DNA molecule. This newly formed DNA-molecule can be amplified by rolling circle amplification. The resulting single-stranded DNA-molecule collapses into a bundle, which is detectable through hybridization of fluorescently labeled complementary oligonucleotides. [ PMID:15155907 PMID::17072308 ]