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[Display omitted] • Binding interaction of CEPS with BSA was investigated using various spectroscopic techniques. • The fluorescence quenching of BSA induced by CEPS was static quenching. • Disruption in the secondary structure conformation of BSA in presence of CEPS. • The esterase activity of BSA was inhibited by CEPS. • Docking study reveals the Preferential binding of CEPS with Sudlow site I. 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 (K sv) 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. [ABSTRACT FROM AUTHOR]

Phosmet exerts its neurotoxicity by inhibiting acetylcholinesterase that catalyzes the degradation of acetylcholine (a neurotransmitter). Serum proteins are known to influence the biodistribution of various endogenous and exogenous compounds. In the present study, the binding interactions of phosmet with bovine serum albumin (BSA) was investigated to determine the free concentration of phosmet for its neurotoxicity. The binding mechanism was studied using fluorescence, UV–Vis absorption spectroscopy, circular dichroism (CD), and molecular docking techniques. UV–Vis absorption data showed an increase in absorbance of BSA upon binding with phosmet with a slight red-shift in the peak around 280 nm. Intrinsic fluorescence of BSA was quenched in the presence of phosmet. The quenching was observed to be inversely correlated to the temperature that indicated the formation of ground state non-fluorescent complex (static quenching). Binding constant values and n values for the binding of phosmet with BSA at three different temperatures confirmed non-covalent binding interactions with a single set of equivalent binding sites. Thermodynamic parameters ∆G (−137.40 ± 3.58 kJ mol−1); ΔH (−16.33 ± 5.28 kJ mol−1) and ΔS(−469 ± 12.45 kJ mol−1) confirmed that the binding was spontaneous and non-covalent interactions like electrostatic, hydrogen bonding and van der Waals forces played an important role in the binding. The CD data indicated the conformational change in BSA upon binding with phosmet which resulted in a change in the melting temperature. Molecular docking presented the binding model for BSA-phosmet complex and displayed that non-covalent interactions played a significant role in the binding mechanism. Unlabelled Image • Spectroscopic and molecular docking techniques were adopted for study. • Fluorescence quenching of BSA upon binding with phosmet • Non-covalent forces and single equivalent binding sites for BSA-phosmet complex • Conformation and melting temperature of BSA changed upon binding with phosmet • Docking presented 3D models for binding of BSA-phosmet complex. [ABSTRACT FROM AUTHOR]