Binding interaction of sodium benzoate food additive with bovine serum albumin: multi-spectroscopy and molecular docking studies

Sodium benzoate (SB) is widely used as a preservative in food industry, and bovine serum albumin (BSA) is a major carrier protein similar to human serum albumin (HSA), the study of the binding between the two has great significance on human health. In this paper, we systematically investigated the binding of SB and BSA under the simulated physiological conditions combining with various common analytical methods, e.g., fluorescence, UV-vis absorption, synchronous fluorescence and circular dichroism (CD) spectra, as well as molecular docking method. The fluorescence quenching measurements were respectively carried out at 298 K, 303 K and 308 K using the Stern-Volmer method. The results reveal that ground state SB-BSA complex was formed within the binding constants from 2.02 × 104 to 7.9 × 103 M-1. Meanwhile, the negative values of ΔH 0 (- 43.92 kJ mol-1) and ΔS 0 (- 111.6 J mol-1 K-1) demonstrated that both the hydrogen binding interaction and van der Waals forces contributed to stabilizing the SB-BSA complex. The site marker competitive experiments show that the SB and BSA bound at site I. Furthermore, the experimental results of UV-vis absorption, synchronous fluorescence and CD spectra indicate that the binding of SB and BSA may change the conformation of BSA. In addition, the molecular docking experiment suggests that hydrogen bond was formed in the interaction between SB and BSA.