title: Biophysical influence of isocarbophos on bovine serum albumin: spectroscopic probing.
abstract: Isocarbophos (ICP) is a phosphorous pesticide with high toxicity. It has been detected in several kinds of food and therefore can enter human body. In this paper, spectroscopic approaches including three-dimensional fluorescence (3D-FL) spectroscopy, UV-visible absorption spectroscopy and circular dichroism (CD) spectroscopy were employed to explore the binding of ICP to bovine serum albumin (BSA) at simulated physiological conditions. It was found that the fluorescence quenching of BSA was caused by the formation of ICP-BSA complex at ground state and belonged to static quenching mechanism. The binding constants, the number of binding sites, enthalpy change (ΔH(θ)), Gibbs free energy change (ΔG(θ)) and entropy change (ΔS(θ)) were calculated at four different temperatures according to Scatchard model and thermodynamic equations. To identify the binding location, fluorescence probe techniques were used. The results showed that warfarin, an acknowledged site marker for BSA, could be partially replaced by ICP when ICP was added to warfarin-BSA systems, which demonstrated that ICP primarily bound on Sudlow's site I in domain IIA of BSA molecule. The distance r (3.06 nm) between donor (Trp-212) and acceptor (ICP) was obtained based on Förster's non-radiation fluorescence resonance energy transfer (FRET) theory. Furthermore, the CD spectral results indicated that the secondary structure of BSA was changed in presence of ICP. The study is helpful to evaluating the toxicology of ICP and understanding its effects on the function of protein during the blood transportation process.
authors.affiliation: College of Chemical and Pharmaceutical Engineering, Jingchu University of Technology, Jingmen, Hubei 448000, People's Republic of China. h.x.zhang@yeah.net
authors.forename: Hua-xin
authors.initials: HX
authors.lastname: Zhang
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhou
authors.forename: E
authors.initials: E
authors.lastname: Liu
mesh_terms: D000818:Animals; D001665:Binding Sites; D002417:Cattle; D002942:Circular Dichroism; D008294:Malathion / Q000031:analogs & derivatives* / Q000378:metabolism; D010575:Pesticides / Q000378:metabolism*; D011485:Protein Binding; D012710:Serum Albumin, Bovine / Q000737:chemistry / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet
chemical_list: D010575:Pesticides; D012710:Serum Albumin, Bovine; C549713:isocarbophos; D008294:Malathion