Scheme 2.

Molecular design of adapters for target cyclization. (A) The structure of long double-stranded adapters. (B) Target cyclization by adapters with the long duplex part. The adapters ligate on both sides of the target so that the cyclization cannot proceed. (C) The structure of short dynamic adapters. (D) Target cyclization by dynamic adapters. The short dynamic adapters ligate at the P* side first, followed by the ligation of another end (cyclization) to the N* side. No ligation between the adapter and the N* side can be carried out directly before the adapter ligated to the P* side. In this way, the cyclization becomes efficient, and the target can be amplified by RCA in the next step.