Probing the interaction mechanism between Direct Red 80 and Human serum albumin: studies at the molecular level

In recent years, azo dyes have received increasing attention due to their adverse effects on the environment and consumer health. However, the interaction mechanism between human serum albumin (HSA) and Direct Red 80 (DR80) is still unknown. The results showed that DR80 changed the secondary structure of HSA and made HSA skeleton loose and stretch. In addition, DR80 quenched the endogenous fluorescence of HSA by static quenching and changed the microenvironment of Trp in form of the hydrophobicity increased and the polarity decreased. Molecular docking results indicated that DR80 bound to the interface of three alpha-helical domains of HSA, hence, the changes in HSA structure and conformation was the main reason for the decline of its esterase activity. This work was done to illuminate the binding mechanism of DR80 and HSA, and to provide a different way for screening the low toxic dye at the molecular level.