Abstract:The interaction of acetycholinesterase (AChE) with 2,4,6-trichlorophenol (2,4,6-TCP) and pentachlorophenol (PCP) was studied by fluorescence and UV-Vis spectroscopy. The Stern-Volmer quenching constants, binding constants, thermodynamic parameters and binding distance were obtained. The intrinsic fluorescences of AChE were quenched regularly by 2,4,6-TCP and PCP, respectively. Static quenching mechanism played the major roles when the temperature was less than 303K. The thermodynamic parameters indicated that the binding reaction was spontaneous and being driven by entropy, and the hydrophobic force played the major roles in the binding of AChE and chlorophenols. The binding distance r between AChE and chlorophenols was 1.91 nm for 2,4,6-TCP and 2.00 nm for PCP, respectively. The binding constants of AChE with 2,4,6-TCP and PCP were in the range of 104~105L/mol. Energy transfer from AChE to 2,4,6-TCP and PCP occurred, and the AChE-chlorophenols complex was formed. The binding reaction between 2,4,6-TCP and AChE was stronger than those between PCP and AChE, which was attributed to the competition between hydrophobic effect and stereo-hindrance effect.