Deciphering the interactions between chlorambucil and calf thymus DNA: A multi-spectroscopic and molecular docking study

• The binding mode between chlorambucil and calf thymus DNA is groove binding.
• The quenching process was found to be static.
• Hydrophobic interaction and hydrogen bonding played major role in the binding.
• There was no significant change in the Tm and secondary structure of DNA.
• Molecular docking study revealed binding energy of −4.869 kcal/mol.

Non-covalent interactions of chlorambucil with calf thymus DNA was investigated using multi-spectroscopic techniques and molecular docking study. Binding constant calculated was found to be 1.54 × 104 M−1 at 290 K, significantly lower than various known intercalators. Quenching process was found to be static as evident by biomolecular quenching constant. Thermodynamic parameters revealed the involvement of hydrophobic interactions and hydrogen bonds in the binding. Chlorambucil was found to interact via external binding mode and follow groove binding as it replaces Hoechst (a typical groove binder) from the groove of DNA but does not replace intercalating dyes including ethidium bromide and acridine orange from the DNA helix. These results were further supported by KI quenching experiments, DNA melting studies, CD spectroscopy and molecular docking.