Figure 1: The fl uorescence intensity of plasmid DNA under berberine derivatives with different concentration. 0– 0 mol/L; 1– 3.9 × 10−6 mol/L; 2– 1.56 × 10−5 mol/L; 3– 6.25 × 10−5 mol/L; 4– 2.5 × 10−4 mol/L.