title: A model for ultracentrifugal quantification of (35-S) bromosulphthalein-binding to plasma proteins in the presence of radioimpurities.
abstract: Sloutions of (35S)bromosulphthalein ((35S)BSP) in heparinized canine plasma, in the proportions established in vivo after injecting BSP intravenously to test liver function, were ultracentrifugated at 226,000 g for 24 hr at 5 degrees.  Protein-free supernatant was replaced by Krebs-Ringer buffer (pH 7.40), the protein sediment resuspended, and the mixture recentrifugated.  That process was repeated several times, and the radio-activity of each resulting supernatant was measured. Since (35-S)BSP could not be adequately purified, supernatant radioactivities reflected both (35-S)BSP and radioimpurity.  Therfore, a model was derived that (i) interpreted the rapid decrease in supernatant radioactivities of initial centrifugations and the gradual fall therafter; and (ii) allowed us to determine picomoles of non-protein-bound (35-S)BSP. Results indicated that only 0.053% (SD .0013%) of BSP in our system was not protein-bound.
mesh_terms: D000818:Animals; D001798:Blood Proteins / Q000378:metabolism*; D002417:Cattle; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D002855:Chromatography, Thin Layer; D004285:Dogs; D006493:Heparin; D008433:Mathematics; D008962:Models, Theoretical; D011485:Protein Binding; D013448:Sulfobromophthalein / Q000302:isolation & purification / Q000378:metabolism*; D013462:Sulfur Radioisotopes; D014461:Ultracentrifugation
chemical_list: D001798:Blood Proteins; D013462:Sulfur Radioisotopes; D013448:Sulfobromophthalein; D006493:Heparin