Spectroscopic Studies on the Interaction of 2,4-Dichlorophenol with Bovine Serum Albumin

Abstract

The interaction between 2,4-dichlorophenol (DCP) and bovine serum albumin (BSA) was investigated by fluorescence spectroscopy combined with UV-vis absorption and circular dichroism (CD) spectroscopy under simulative physiological conditions. The experiment results show that the fluorescence intensity of BSA is dramatically decreased owing to the formation of a DCP–BSA complex. The corresponding effective quenching constants (K a) between DCP and BSA at four different temperatures (292, 298, 304 and 310 K) were determined to be 10.08×104, 9.082×104, 8.177×104, and 7.260×104 L⋅mol−1, respectively. The thermodynamics parameters enthalpy change (ΔH) and entropy change (ΔS) were calculated to be −13.64 kJ⋅mol−1 and 49.08 J⋅mol−1⋅K−1, which suggested that hydrophobic interaction was the predominant intermolecular force. Site marker competitive experiments indicated that the binding of DCP to BSA primarily takes place in subdomain IIA. The binding distance (r) between DCP and the tryptophan residue of BSA ias 4.09 nm according to Forster’s theory of non-radioactive energy transfer. The conformational investigation demonstrated that the presence of DCP decreased the α-helical content of BSA and induced a slight unfolding of the polypeptides of protein, which confirmed the occurrence some micro environmental and conformational changes of BSA molecules.