Fig. 1. KRAS-G4 and its interaction with berberine and coptisine.

a Schematic of the human KRAS gene promoter and the formation of a KRAS-G4 as well as its complex with small molecules (ligands). The G4-forming region of the NHE sequence is shown. The G-tracts implicated in KRAS-G4 formation are marked in red and mutations in cyan, respectively. b Chemical structures of berberine and coptisine with numbering. c 1D ¹H NMR titration of Pu24m1 DNA with berberine and coptisine, respectively, with complete imino proton assignment. Conditions: 150 μM DNA, pH 7, 50 mM K⁺ solution, 25 °C, DMSO-d₆ < 1.5%.