Luminescence Spectroscopy of Conjugation Reaction between Bovine Serum Albumin and Spectroscopic Probe Ponceau S

Ponceau S(PS) can quench the fluorescence of bovine serum albumin (BSA) in the aqueous solution of pH=7.40. The static fluorescence quenching process between BSA and PS was confirmed and the binding constant, the number of binding sites and thermodynamic parameters between BSA and PS were obtained. It showed that the number of binding sites was 1 and the electrostatic attraction played an important role in the binding of BSA to PS. Based on the theory of Forester energy transfer, the binding distance (r＜7.0 nm) between PS and BSA was obtained. Studies utilizing synchronous spectra showed that the conjugation reaction between PS and BSA would affect the conformation of BSA, leading to the weak polarity around tyrosine residues and the strong hydrophobicity. The site markers competitive experiments indicated that the binding of PS to BSA primarily took place in sub-domain ⅡA (site Ⅰ).