Mechanistic investigation of bead-based padlock rolling circle amplification under molecular crowding conditions.

We present a mechanistic investigation of bead-based padlock rolling circle amplification (RCA) under molecular crowding conditions, a sensitive and selective DNA detection method we have developed. Several important points to optimize the method were clarified: (i) the increase in the number of RCA products is proportional to the excluded volume of poly(ethylene glycol) (PEG), (ii) PEG facilitates ligation of padlock probe to form circular concatemers and monomers, both of which may act as a template for RCA, and (iii) hybridization of detection probe to the products may be facilitated at higher PEG concentrations.