Figure 6.

PLA system: procedure. (A) When the distance between two targets is more than 40 nm, PLUS oligo and MINUS oligo, which is linked to primary or secondary antibodies, cannot hybridize with each other; (B) When these probes are present at less than 40 nm, they hybridize and then ligate to form a circle; (C) The DNA circle undergoes several hundredfold replication by the rolling-circle amplification (RCA) reaction; (D) The fluorescently labeled oligonucleotides will hybridize to the RCA product. In this Scheme, as an example, heterodimer of ERα and ERβ induced by estrogen-binding (pink) are depicted.