Spectroscopic studies and molecular modelling of the aflatoxin M1-bovine α-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 α-lactalbumin (α-La) and AFM1 using different spectroscopic methods coupled with molecular docking studies. Fluorescence spectroscopy measurements demonstrated the AFM1 addition considerably reduced the α-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 α-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 ΔH, ΔS and ΔGb 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 α-La secondary structures when the α-La-AFM1 complex was formed. An increased content of the α-helix structures (from 35 to 40%) and the β-sheets (from 16 to 19%) were observed. Furthermore, protein-ligand docking modelling demonstrated AFM1 could bind to the hydrophobic regions of α-La protein. Overall, the gathered results confirmed the α-La-AFM1 complex formation. [Display omitted] •Interaction of AFM1 and α-La was studied by in vitro and in silico methods.•The formation of a complex between AFM1 and α-La by spectroscopy methods was demonstrated.•Thermodynamics parameters demonstrated that the interaction is hydrophobic.•The interaction of AFM1 with α-La causes ordering of its secondary structures.•Two possible binding sites for AFM1 on α-La was founded by molecular docking.