Study on the interaction of food colourant quinoline yellow with bovine serum albumin by spectroscopic techniques.

The interaction of a food colourant, quinoline yellow (Qy), and bovine serum albumin (BSA) was investigated by spectrophotometry, spectrofluorometry, FT-IR and circular dichroism (CD) techniques. The experimental results indicated that the quenching mechanism of BSA by the dye was a static procedure. Various binding parameters were evaluated. The negative value of ΔH, negative value of ΔS and the negative value of ΔG indicated that van der Waals force and hydrogen bonding play major roles in the binding of Qy and BSA. Based on Forster's theory of non-radiation energy transfer, the binding distance, r, between the donor (BSA) and acceptor (Qy) was evaluated. The results of CD and UV-vis spectroscopy showed that this dye could bind to BSA and the conformation of BSA changed.