Fig. 1
Taq DNA polymerase stop assay showing the stabilization of the RET G-quadruplex with berberine and its structural analogues. a Structures of berberine and its analogues. b Sequence of the single-stranded template DNA annealed with the 5′-[32P] labelled primer used in DNA polymerase stop assay. c DNA polymerase stop assay at increasing concentrations of berberine (0, 0.75, 1.5, 15 μg/ml) and its analogues (0, 0.75, 1.5,3, 15 μg/ml). Lanes A, G, T & C represent the di-deoxy sequencing reactions with the same template, which serve as the marker to identify the exact stop site. Lane P represents the position of the free primer on the gel