Deciphering the interaction of flavones with calf thymus DNA and octamer DNA sequence (CCAATTGG)2

Abstract

We investigated the interaction of three flavone compounds, baicalein, chrysin and flavone with calf thymus DNA and octamer DNA sequence (CCAATTGG)₂. The binding mechanisms of the flavone compounds with both DNA were unveiled using biophysical, thermodynamic and molecular modelling techniques. Absorption and fluorescence titrations confirm the formation of the DNA complexes along with the extent of interaction. Absorption data proposed an intercalation mode of binding. Fluorescence displacement assays using ethidium bromide and Hoechst 33258 data supports a partial intercalation. Potassium iodide quenching substantiated this finding. Circular dichroism data revealed major structural changes on binding with flavones which can arise from intercalation partially or in a tilted arrangement. Analysis of the effect of ionic strength on complex formation eliminated the role of electrostatic interaction in the binding. Differential scanning calorimetric data showed substantial changes in the melting temperatures of complexes and predicted the DNA–baicalein complex as the most stable one. Molecular modelling showcased that the complexes are located near the AT rich region. Docking analysis with different sequences showed that the flavone compounds intercalated with base pairs only with d(CGATCG)₂.