title: Thyroxine-binding globulin: characterization of the binding site with a fluorescent dye as a probe.
abstract: The fluorescent dye 1,8-anilinonaphthalenesulfonate competed with thyroxine for binding to thyroxine-binding globulin. Fluorescence analysis indicated that the dye bound to the globulin in a molar ratio of 1:1 and with an association constant (at 23 degrees C) of 4.19 x10(6)M(-1), and that thyroxine bound to the globulin in a molar ratio of 1:1 and with an association constant (at 23 degrees C) of 2.35x10(10)M(-1). Displacement of globulin-bound dye by thyroxine was shown by fluorescence quenching, and displacement of globulin-bound thyroxine by dye was demonstrated by ultrafiltration.
mesh_terms: D001665:Binding Sites; D004735:Energy Transfer; D005374:Filtration; D005456:Fluorescent Dyes / Q000378:metabolism*; D008970:Molecular Weight; D009905:Optical Rotatory Dispersion; D011485:Protein Binding; D013057:Spectrum Analysis; D013696:Temperature; D013974:Thyroxine / Q000378:metabolism; D013975:Thyroxine-Binding Proteins / Q000378:metabolism*
chemical_list: D005456:Fluorescent Dyes; D013975:Thyroxine-Binding Proteins; D013974:Thyroxine