Spectroscopic studies and molecular modelling of the aflatoxin M1-bovine ?-lactalbumin complex formation.

Since the high incidence of aflatoxin M1 (AFM1) in milk and dairy products poses a serious risk to human health, this work aimed to investigate the complex formation between bovine ?-lactalbumin (?-La) and AFM1 using different spectroscopic methods coupled with molecular docking studies. Fluorescence spectroscopy measurements demonstrated the AFM1 addition considerably reduced the ?-La fluorescence intensity through a static quenching mechanism. The results indicated on the endothermic character of the reaction, and the hydrophobic interaction played a major role in the binding between AFM1 and ?-La. The binding site stoichiometric value (n = 1.32) and a binding constant of 2.12 × 103 M?1 were calculated according to the Stern-Volmer equation. The thermodynamic parameters ?H, ?S and ?Gb were determined at 93.58 kJ mol?1, 0.378 kJ mol?1 K?1 and -19.17 0.96 kJ mol?1, respectively. In addition, far-UV circular dichroism studies revealed alterations in the ?-La secondary structures when the ?-La-AFM1 complex was formed. An increased content of the ?-helix structures (from 35 to 40%) and the ?-sheets (from 16 to 19%) were observed. Furthermore, protein-ligand docking modelling demonstrated AFM1 could bind to the hydrophobic regions of ?-La protein. Overall, the gathered results confirmed the ?-La-AFM1 complex formation