The electronic-embedding model of the two layered ONIOM (ONIOM-EE) method was used for single point energy calculation using the B3LYP hybrid DFT functional along with 6-31++G basis set for the QM region and AMBER force field for the MM region. The single point energy of QM region in the gas phase using the same method was also calculated. The interaction energy between the DNA and drug was calculated using above mentioned formula.