Investigation on the interactions of contaminant triclosan with human serum albumin: Spectroscopic and molecular docking studies

Abstract

Triclosan (TCS) is an extensively distributed environmental contaminant that can have impacts on ecosystems and human health. This study employed both in vitro experiments and computer simulations to assess the interaction between TCS and human serum albumin (HSA) at the molecular level. The formation of the HSA-TCS complex was a spontaneous process, maintained by strong affinity (Ka > 105) due to hydrogen bonds and van der Waals forces. TCS binding to the I site of HSA led to an increase in hydrophobicity around the Trp-residue and altered the structure of the peptide chain backbone. CD spectroscopy revealed alterations in the secondary structure of HSA, including decreased α-helical content and increased disorder, in the presence of TCS. Moreover, the esterase activity in HSA was inhibited by TCS as an anticompetitive inhibitor. Molecular docking studies identified TCS tightly embedded at site I of HSA, with binding facilitated through hydrogen bonds and hydrophobic interactions. Molecular dynamics simulations highlighted the significant energy contributions of Trp214 and Lys199 residues, directly involved in the formation of the HSA-TCS complex. Additionally, the presence of TCS enhanced the compactness of the HSA structure. Therefore, new insights into toxicological studies of other contaminants can be proposed based on these results of TCS.