title: Binding studies of pyriproxyfen to DNA by multispectroscopic atomic force microscopy and molecular modeling methods.
abstract: In this work, multispectroscopic atomic force microscopy and molecular modeling [ONIOM 2(B3LYP/6-31++G(d,p): Universal Force Field (UFF)) level] techniques were used to study the interaction between Calf-Thymus-DNA (CT-DNA) and pyriproxyfen (PYR) insecticide. The binding constant of PYR with double-strand deoxyribonucleic acid (ds-DNA) was obtained by ultraviolet-visible absorbance spectroscopy as 2.8×10(4) at 20°C. Thermodynamic parameters, that is, ΔH, ΔS°, and ΔG, were -53.82 kJ mol(-1), 96.11 J mol(-1), and -82.46 KJ mol(-1), respectively. Thermal denaturation study of DNA with PYR revealed the ΔT(m) of 3.0 and 6.0°C at r(i)=0.5 and 1.0, respectively. The Fourier transform infrared study showed a major interaction of PYR with G-C and A-T base pairs and a minor perturbation of the backbone PO(2) group. Further, PYR induces detectable changes in the circular dichroism spectrum of CT-DNA. In fluorimetric studies, the dynamic enhancement constants (k(D)) and bimolecular enhancement constant (k(B)) were calculated, which showed that the fluorescence enhancement was initiated by a static process in the ground state. The hybrid of quantum mechanical/molecular mechanics theoretical calculations revealed that the interaction is base sequence dependent, and PYR interacts more with DNA via the AT base sequence. From the data we concluded that PYR may interact with ds-DNA via two modes: intercalating and outside groove binding.
authors.affiliation: Department of Medicinal Chemistry, Faculty of Pharmacy, Kermanshah University of Medical Sciences, Kermanshah, Iran.
authors.forename: Farhad
authors.initials: F
authors.lastname: Ahmadi
authors.forename: Nasibeh
authors.initials: N
authors.lastname: Jamali
authors.forename: Rostam
authors.initials: R
authors.lastname: Moradian
authors.forename: Bandar
authors.initials: B
authors.lastname: Astinchap
mesh_terms: D000818:Animals; D001665:Binding Sites; D002417:Cattle; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D007364:Intercalating Agents / Q000737:chemistry / Q000378:metabolism; D018625:Microscopy, Atomic Force; D008954:Models, Biological; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D011725:Pyridines / Q000737:chemistry* / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet
chemical_list: D007364:Intercalating Agents; D011725:Pyridines; C055613:pyriproxyfen; D004247:DNA; C427203:calf thymus DNA