Modulation of accessibility of subdomain IB in the pH-dependent interaction of bovine serum albumin with cochineal red A: A combined view from spectroscopy and docking simulations

Our recent report on the binding of Cochineal Red A, a food dye, with HSA and BSA at pH 7.4 has revealed that electrostatic forces is the principal cause of interaction. In that study issues relating to complications arising out of modulation of dye binding affinity of BSA with pH had not been explored. Here we have further explored the interaction of Cochineal Red A with BSA in pH range 4.8-7.8. Surprisingly, this system behaves differently in the texture of interaction pattern at two extremes of studied pH range, unlike HSA. Importantly, the charge on the amino acid side chains in the binding pocket is likely to play a significant role.