Fluorescence spectroscopy and molecular modeling studies on the interaction of aflatoxin B۱ and G۱ with bovine α-lactalbumin

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 B۱ (AFB۱) and Aflatoxin G۱ (AFG۱) 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 AFB۱ and AFG۱ with the ALA protein was studied using fluorescence spectroscopy, molecular docking and molecular dynamic (MD) simulation. The spectroscopy experiments showed that the interaction with AFB۱ and AFG۱significantly 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 –۵.۳۲ kcal per mol and ۰.۸۰ × ۱۰۴ L mol-۱ for AFB۱ and -۵.۶۴ kcal per mol and ۱.۳۵ × ۱۰۴ l mol-۱ for AFG۱, 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 AFB۱ and AFG۱ 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, AFB۱and AFG۱ could form complex with ALA, however, AFG۱ showed higher affinity for binding to ALA and more compact complex structure.

کلیدواژه ها:

α-Lactalbumin ، Aflatoxins ، Fluorescence spectroscopy ، Molecular Docking ، Molecular dynamic simulation