Binding Characteristics of a Thyroid Hormone Metabolite, 3, 3'-Diiodo-L-thyronine, to Bovine Serum Albumin as Measured by Fluorescence

Abstract

The interaction between a thyroid hormone metabolite, 3, 3'-diiodo-L-thyronine(3, 3'-T₂) and bovine serum albumin (BSA) was investigated by the fluorescence method. The apparent binding constants and thermodynamic parameters were obtained assuming the equivalence and independence of the binding sites on the BSA molecule. The maximum binding was attained at near pH 8.5 and the apparent binding constant at pH 8.5 was 2.7 (0.2)×10⁵M<-1>. The standard free energy change, enthalpy change and entropy change were -7.36 (0.02) kcal mol^-1, -7.75 kcal mol^-1 and -1.51 e, u., respectively.