title: [Thyroid hormone conjugates with rhodamine B as fluorescent ligands of human plasma transport proteins].
abstract: Conjugates of thyroxine (T4) and triiodothyronine (T3) with rhodamine B in which the hormone and the fluorescent dye are linked via a thiourea bond have been synthesized. These conjugates possess an ability to inhibit in a competitive manner the binding of [125I]T4 to three protein preparations: T4-binding globulin (TBG), apolipoprotein A-I (ApoA-I), and high density lipoprotein particles (ApoA-I-HDL) isolated from human serum by T4-Sepharose 4B chromatography and further purified. The following values of association constants have been estimated: for the T4 derivative-3 x 10(7) M-1 (TBG), 4.1 x 10(5) M-1 (ApoA-I), and 4.2 x 10(5) M-1 (ApoA-I-HDL); for the T3 derivative-1.6 x 10(7) M-1 (TBG), 5.3 x 10(5) M-1 (ApoA-I), and 5.4 x 10(5) M-1 (ApoA-I-HDL). The binding of rhodamine B-labeled thyroid hormones to TBG or ApoA-I do not alter significantly the parameters of rhodamine B chromophore absorption and fluorescence. The interaction of the conjugates with ApoI-HDL leads to a significant enhancement of the absorption intensity and a 3 nm blue shift in the absorption maximum as well as to a 1.5-fold increase in the fluorescence band amplitude at 586 nm. Biological and fluorescent properties of T4 and T3 derivatives suggest that these compounds may be a useful tool in fluorescence studies of plasma binding protein-driven transport of thyroid hormones in model biological systems.
authors.forename: M N
authors.initials: MN
authors.lastname: Ermolenko
authors.forename: N A
authors.initials: NA
authors.lastname: Fil'chenkov
authors.forename: O V
authors.initials: OV
authors.lastname: Sviridov
mesh_terms: D001667:Binding, Competitive; D001692:Biological Transport; D001798:Blood Proteins / Q000378:metabolism*; D002846:Chromatography, Affinity; D005456:Fluorescent Dyes / Q000737:chemistry*; D006801:Humans; D008024:Ligands; D012235:Rhodamines / Q000737:chemistry*; D013963:Thyroid Hormones / Q000737:chemistry* / Q000378:metabolism
chemical_list: D001798:Blood Proteins; D005456:Fluorescent Dyes; D008024:Ligands; D012235:Rhodamines; D013963:Thyroid Hormones; C029773:rhodamine B