Fig. 6. 2D NMR spectra of KRAS–G4 in complex with berberine and coptisine.

Select regions of the 2D-NOESY spectra of 3:1 berberine-KRAS-G4 (a) and 2.5 :1 coptisine-KRAS-G4 (b) complexes in H₂O showing intermolecular cross-peaks between compound and DNA imino protons. Conditions: 1.5 mM Pu24m1 DNA, pH 7, 50 mM K⁺ solution, 35 °C, DMSO-d₆ < 3.5%.