title: Effect of divalent metal ions on the binding of thyroxine to bovine serum albumin as measured by fluorescence.
abstract: The binding of thyroxine (T4) to bovine serum albumin (BSA) has been studied in the presence and absence of Ca2+, Cu2+ and Zn2+ ions at various pH's in 0.1 M Tris-acetate buffer at 25 degrees C using the fluorescence method. In the presence of 50 microM Ca2+ and Zn2+ and the absence of metal ions, the binding constant (K) increased similarly with increasing pH values from pH 5 to pH 9, and the K value near midpoint, pH 7.4, was 1.66 +/- 0.17 x 10(6) M-1. By contrast, the binding constant remained constant between pH5 and pH9 in the presence of 10 microM Cu2+, with an average value of 1.61 +/- 0.22 x 10(6) M-1, suggesting a significant influence of Cu2+ ions on T4 binding to BSA.
authors.affiliation: Faculty of Pharmaceutical Sciences, Kinki University, Osaka, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Okabe
authors.forename: M
authors.initials: M
authors.lastname: Hokaze
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002413:Cations, Divalent / Q000494:pharmacology*; D002417:Cattle; D003300:Copper / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D011485:Protein Binding; D012710:Serum Albumin, Bovine / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D013974:Thyroxine / Q000378:metabolism*; D015032:Zinc / Q000494:pharmacology
chemical_list: D002413:Cations, Divalent; D012710:Serum Albumin, Bovine; D003300:Copper; D015032:Zinc; D013974:Thyroxine; D002118:Calcium