Spectroscopic studies of binding interactions of 2-chloroethylphenyl sulphide with bovine serum albumin

Sulphur mustard is a lethal chemical warfare agent, known for its vesicant or blistering action on skin and mucous membrane. 2-chloroethylphenyl sulphide (CEPS) is a simulant of sulphur mustard. In the present study, the binding interaction of CEPS with bovine serum albumin (BSA) was investigated to determine its binding potential with skin proteins. The binding interactions studies were performed using UV–Vis absorbance, steady-state fluorescence, synchronous fluorescence, circular dichroism techniques. It is observed in UV–Vis absorption study, absorbance of BSA at 280 nm increases with a slight blue shift in the presence of CEPS indicated a complex formation between CEPS and BSA. Fluorescence quenching of emission intensity of BSA in the presence of CEPS indicated change in the microenvironment of fluorophores (Tryptophan residues). Stern-Volmer plot showed an inverse relationship between quenching (Ksv) and temperature. Thus, the quenching is operative via static quenching. The binding parameters suggested the role of non-covalent interactions and involvement of single set of equivalent binding sites. Change in thermodynamic parameters suggested that the binding is essentially enthalpy driven and spontaneous in nature. A synchronous fluorescence of BSA spectra in the presence of CEPS causes maximum change around the microenvironment of Tryptophan residues than Tyrosine residues. The intermolecular distance between the donor (BSA) and acceptor (CEPS) molecule was 3.5 nm as calculated from FRET analysis and indicated no significant transfer of energy between donor and acceptor. CD spectrum confirmed the changes in secondary structure of BSA upon binding with CEPS. The esterase enzyme activity of BSA in presence of CEPS showed a decrease in enzyme activity. The binding interactions were modeled in binding pockets using molecular docking calculations.