Multi-spectroscopies and molecular simulation insights into the binding of bovine serum albumin and sodium tripolyphosphate

Sodium tripolyphosphate (STPP) is an odorless and water-soluble anionic mineral compound. STPP is used as a separator, texturizer, emulsifier and buffer in the food and detergent industries. Considering the importance of the topic and the interaction of food additives with biological molecules including blood serum albumin, we investigated the binding properties of STPP food additive to blood serum albumin through UV-Vis spectroscopy, fluorescence spectroscopy, Fourier transform infrared spectroscopy (FT-IR), and molecular docking analysis. According to the results, after forming a complex with BSA, STPP reduced the fluorescence intensity of BSA through static quenching mechanisms, and the UV-Vis absorption results were also confirmatory. Synchronous fluorescence and FT-IR results showed that the microenvironment and secondary structure of BSA changed in the presence of STPP. The synchronous fluorescence study has shown that the quenching toward Trp residue is higher than Tyr residue. The thermodynamic results showed that van der Waals force and hydrogen bonding play the main roles in the formation of the STPP-BSA complex. The binding constant decreases from 2.23 x 106 to 4.25 x 101 (M-1) with increasing temperature, indicating a decrease in complex formation due to the interaction of STPP with BSA. Furthermore, molecular docking studies showed that STPP binds to the cavity between domains IIIA and IIIB by van der Waals forces and hydrogen bonds through residues Ser 418, Thr 419, Tyr 496, Lys 499, and Lys 533.