Investigation The Interaction Of Food Additives With BSA By Spectral Method And Debye-h(?)ckel Limiting Law

Natamycin, nisin, fast green FCF(FCF), patent blue V(PBV), acid blue 1(AB1), acid red 1(AR1) and acid green 50(AG50) are common food additivies, where natamycin and nisin are used as food preservative, while The other five are used as food colourants. In this study, the interaction of the seven food additives with bovine serum albumin(BSA) were investigated by the multiple spectroscopic techniques(including fluorescence, UV-vis absorption and FTIR spectra) for understanding the the chemical absorption, distribution and transportation of the seven food additives in plasma protein. The research indicated that the quenching mechanism between BSA and natamycin or nisin was a static quenching or combined quenching(static and dynamic) process, and the BSA-natamycin/nisin complex was formed in this process. The binding constants, the number of binding sites and the binding distance of the two systems were calculated. Meanwhile, the displacement experiments indicated that natamycin/nisin primarily bound to Trp-212 residue of BSA. The thermodynamic parameters showed that the two binding process were spontaneous, and the binding of natamycin to BSA mainly depended on hydrophobic interaction, yet the binding of nisin to BSA strongly relied on Van der Waals forces and hydrogen bond. In addition, the effects of some common ions on the quenching constants of BSA-natamycin/nisin system were also investigated.The five food colourants(FCF, PBV, AB1, AR1 and AG50) quenched the intrinsic fluorescence of BSA by a static process in different pH and/or salt concentrations. The electrostatic force dominated the formation of BSA-FCF/PBV/AB1/AR1/AG50 complex and the interactions process of BSA with the five food colourants were spontaneous, which were confirmed by the thermodynamic parameters and the effects of salt on their interactions. In different studied conditions, AR1/AG50 bound to the Trp-212 residue of BSA. However, Trp-212 residue was the primary binding site for FCF/PBV/AB1 on BSA in the pH range of 5.5-7.4, both Trp-212 and Trp-134 residues of BSA might be bound by FCF/PBV/AB1 at pH 4.8. The K values at the same condition suggested that the binding ability of the five food colourants with BSA was FCF > PBV > AB1 and AR1 > AG50. Simultaneously, the results of UV-vis absorption, synchronous fluorescence, 3D fluorescence and FT-IR spectra proved that the structure of BSA altered by the seven food additives.Additionly, the interaction of AR1/AG50 with BSA was investigated through Debye-Hu?ckel limiting law. The true thermodynamic binding constant(Keq), true free energy change(ΔG0Iâ†'0), and effective charge(ZP) in the anion receptor pocket of BSA were calculated. We found that the local charge bound by the two food colourants rather than the overall or surface charge of BSA played a key role in determining the interaction strength of BSA with AR1/AG50. Moreover, the thermal and structural stabilization of BSA was also discussed by analyzing the values of Tm and Hurea without/with the addition of AR1/AG50, respectively.