Study on the interaction between sulfamerazine and human serum albumin on molecular level using spectral analysis

As an important class of veterinary drugs, the extensive usage and massively release into the environment of sulfonamides have led to the resistance of microorganisms to these chemicals and eco-environmental risks. The interaction between sulfamerazine (SM1) and human serum albumin (HSA) under the condition of human blood acidity (pH 7.4) has been studied by fluorescence, synchronous fluorescence, three-dimensional (3D) fluorescence spectroscopy as well as circular dichroism (CD) spectroscopy analysis, and molecular docking analysis. The static quenching and the binding results verify the formation of the SM1-HSA complex with only one binding site. Spectral analysis indicates that the binding site is located in the hydrophobic cavities of IIA subdomains of HSA (site I). The conformation change on its secondary structures alters the microenvironment around Trp and Tyr residues. Hydrogen bonds formed between SM1 and Lys199 can be mainly attributed to the binding of SM1 into subdomain IIA (Sudlow's site I). This study would provide a window to better understand the potential human health risks of sulfonamides. [Display omitted] •Sulfamethazine can combine with human serum albumin to form complex at pH 7.•The formed SM1-HSA complex has only one binding site located in Sudlow's site I.•Hydrogen bond force is the main interaction force.•Sulfamethazine can change the microenvironment tryptophan and tyrosine residues.