Fluorescence spectroscopy and molecular modeling studies on the interaction of aflatoxin B1 and G1 with bovine α-lactalbumin.

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Aflatoxins are toxic chemicals produced by Aspergillus fungi. Reports exist on the relationship of aflatoxin exposure via contaminated food and feed to hepatotoxicity and liver cancer. Aflatoxin B1 (AFB1) and Aflatoxin G1 (AFG1) are two dangerous types of aflatoxins for human health. Bovine α-lactalbumin (ALA) is the second major whey protein in milk which bear diverse biological functions. In this study, the interaction of AFB1 and AFG1 with the ALA protein was studied using fluorescence spectroscopy, molecular docking and molecular dynamic (MD) simulation. The spectroscopy experiments showed that the interaction with AFB1 and AFG1significantly quenched the intrinsic fluorescence emission of ALA via a static quenching mechanism. The free energy of binding and binding constant (Ka) obtained from the intrinsic fluorescence results were -5.32 kcal per mol and 0.80 × 104 L mol-1 for AFB1 and -5.64 kcal per mol and 1.35 × 104 l mol-1 for AFG1, respectively. Molecular docking studies were conducted before and after the MD simulation to estimate the binding sites, Ka s and binding mode. Results from the molecular docking showed that AFB1 and AFG1 bound to ALA via hydrophobic interaction and hydrogen bond. After MD simulation, the precision of the Ka obtained from the docking results was improved and it was more similar to the experimental results of fluorescence spectroscopy. Other simulation results were aligned well with the molecular docking and fluorescence spectroscopy results. Accordingly, AFB1and AFG1 could form complex with ALA, however, AFG1 showed higher affinity for binding to ALA and more compact complex structure.