Some properties of the interaction between 2,2′-diselenadibenzoic acid and serum albumins

The binding of 2,2′-diselenadibenzoic acid to bovine serum albumin (BSA) and human serum albumin (HSA) was studied by using fluorescence spectroscopy. The measurement was performed in Tris-HCl buffer aqueous medium at pH = 7.40. The quenching constant at 303 K was (3.277 ± 0.046) × 1013 L mol−1 s−1 for BSA, and (3.946 ± 0.002) × 1012 L mol−1 s−1 for HSA. Decreased quenching was observed in association with increased temperature. Our findings show that the observed binding constant is dependent on the ionic strength of the medium. It is said that electrostatic interactions play a role in the binding of 2,2′-diselenadibenzoic acid to serum albumin, in addition to the hydrophobic association. The decrease of the linearity of S-V plot demonstrates reduced binding of ligand to the protein in the presence of anionic surfactants such as sodium dodecyl sulfate (SDS), which indicates that 2,2′-diselenadibenzoic acid most likely binds to the hydrophobic pockets within sub-domain IIA of serum albumin, the same site as SDS.