Proposed model for in vitro interaction between fenitrothion and DNA, by using competitive fluorescence, 31P NMR, 1H NMR, FT-IR, CD and molecular modeling

In this work we proposed a model for in vitro interaction of fenitrothion (FEN) with calf thymus-DNA by combination of multispectroscopic and two dimensional molecular modeling (ONIOM) methods. The circular dichroism results showed that FEN changes the conformation of B-DNA and caused some changes to C-DNA form. The FT-IR results confirmed a partial intercalation between FEN and edges of all base pairs. The competitive fluorescence, using methylene blue as fluorescence probe, in the presence of increasing amounts of FEN, revealed that FEN is able to release the non-intercalated methylene blue from the DNA. The weak chemical shift and peak broadening of 1H NMR spectrum of FEN in the presence of DNA confirmed a non-intercalation mode. The 31P NMR showed that FEN interacts more with DNA via its -NO2 moiety. The ONIOM, based on the hybridization of QM/MM (DFT, 6.31++G (d,p)/UFF) methodology, was also performed by Gaussian 2003 package. The results revealed that the interaction is base sequence dependent, and FEN interacts more with AT base sequences.

► A model for in vitro interaction of fenitrothion (FEN) with is proposed. ► The CD results shows a remarkable change in DNA conformasion. ► The 31P NMR signals shows FEN may have more interactions via the phenyl ring. ► The FT-IR spectra shows the FEN partial intercalated via hydrogen binding. ► The ONIOM data represented the interactions is base sequence dependence.