title: Multi-spectroscopic methods combined with molecular modeling dissect the interaction mechanisms of ractopamine and calf thymus DNA.
abstract: The toxic interaction of ractopamine (RAC) with calf thymus DNA (ct DNA) was studied in vitro using multi-spectroscopic methods and molecular modeling methods. The hypochromic effect without a noticeable shift in UV-vis absorption indicated that the minor groove binding mode existed in the interaction between RAC and DNA. The fluorescence quenching of RAC was observed with the increasing addition of DNA and was proved to be the static quenching. The binding constant and the binding site sizes were 4.13 × 10(3) and 0.97, respectively. The thermodynamic calculation demonstrated that the hydrogen bond and van der Waals were main acting forces. This result further confirmed the existence of groove binding mode. Afterwards, we found another interaction mode, electrostatic binding mode through the fluorescence polarization, ionic effects and denatured DNA experiments. Circular dichroism spectroscopy (CD) was then employed to monitor the conformation changes of DNA. Molecular modeling studies illustrated the visual display of the binding mode and the detailed information of the H-bond.
authors.affiliation: Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, China-America CRC for Environment & Health, Shandong Province, Shandong University, 27# Shanda South Road, Jinan 250100, P.R.China.
authors.forename: Jun
authors.initials: J
authors.lastname: Chai
authors.forename: Juyuan
authors.initials: J
authors.lastname: Wang
authors.forename: Qifei
authors.initials: Q
authors.lastname: Xu
authors.forename: Fang
authors.initials: F
authors.lastname: Hao
authors.forename: Rutao
authors.initials: R
authors.lastname: Liu
mesh_terms: D000818:Animals; D001665:Binding Sites; D002417:Cattle; D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry* / Q000378:metabolism*; D006860:Hydrogen Bonding; D008956:Models, Chemical; D008958:Models, Molecular; D009690:Nucleic Acid Conformation / Q000187:drug effects*; D009691:Nucleic Acid Denaturation; D010627:Phenethylamines / Q000378:metabolism* / Q000494:pharmacology*; D013057:Spectrum Analysis / Q000379:methods; D013816:Thermodynamics
chemical_list: D010627:Phenethylamines; C060897:ractopamine; D004247:DNA; C427203:calf thymus DNA