Comparison of interaction between three similar chalconoids and α-lactalbumin: Impact on structure and functionality of α-lactalbumin.

Interaction between α-lactalbumin (α-LA) and three similar chalconoids was compared using a combination of multi-spectral analysis and molecular docking, and their influence on structure and functional properties of α-LA was also investigated. Chalconoids strongly quenched α-LA fluorescence in a static mode and their binding constants to α-LA were declined in the order of hydroxy safflower yellow A (SYA), neohesperidin dihydrochalcone (NHDC) and naringin dihydrochalcone (NGDC). The main interaction forces involved in the binding of SYA, NHDC and NGDC to α-LA included hydrophobic forces and hydrogen bonds. There was non-radiative energy transfer between α-LA and three chalconoids, as indicated by the estimated by Förster's distance. The vicinity of SYA to tryptophan residues of α-LA showed the minimum value. Based on Fourier transform infrared spectroscopy (FTIR) spectra, SYA induced the conversion of more α-LA from α-helix into its β-structures than NHDC and NGDC. Also, although the addition of three chalconoids had no significant effect on the emulsifying activity of α-LA, it slightly improved the emulsion stability of α-LA. In addition, SYA showed the maximum decrease on surface hydrophobicity of α-LA. Antioxidant capacity of SYA was also decreased more than that of NHDC and NGDC after the binding to α-LA. Additionally, docking studies indicated that SYA, NHDC and NGDC bound to the cleft between α-domains and β-domains by three, two and two hydrogen bonds, respectively. Therefore, these findings suggest that there are significant differences among the effects of three similar chalconoids on structure and functionality of α-LA.