The effect of dimerization on the interaction of ibuprofen drug with calf thymus DNA: Molecularmodeling and spectroscopic investigation

The interaction between the dimer structure of ibuprofen drug (D-IB) and calf thymus DNA under simulative physiological conditions was investigated with the use of Hoechst 33258 and methylene blue dye as spectral probes by the methods of UV-visible absorption, fluorescence spectroscopy, circular dichroism spectroscopy and molecular modeling study.Using the Job's plot, a single class of binding sites for theD-IB on DNA was put in evidence. The Stern–Volmer analysis of fluorescence quenching data shows the presence of both the static and dynamic quenching mechanisms. The binding constants, K_b were calculated at different temperatures, and the thermodynamic parameters ?G^°, ?H^° and ?S^° were given. The experimental results showed that D-IB molecules could bind with DNA via groove binding mode as evidenced by: I. DNA binding constant from spectrophotometric studies of the interaction of D-IB with DNA is comparable to groove binding drugs. II. Competitive fluorimetric studies with Hoechst 33258 have shown that D-IB exhibits the ability of this complex to displace with DNA-bounded Hoechst, indicating that it binds to DNA in strong competition with Hoechst for the groove binding. III. There is no significantly change in the absorption of the MB-DNA system upon adding the D-IB, indicates that MB molecules are not released from the DNA helix after addition of the D-IB and are indicative of a non-intercalative mode of binding. IV. Small changes in DNA viscosity in the presence of D-IB, indicating weak link to DNA, which is consistent with DNA groove binding. As well as, induced CD spectral changes, and the docking results revealed that groove mechanism is followed by D-IB to bind with DNA.