A model for ultracentrifugal quantification of (35-S) bromosulphthalein-binding to plasma proteins in the presence of radioimpurities.
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.
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
D001798:Blood Proteins; D013462:Sulfur Radioisotopes; D013448:Sulfobromophthalein; D006493:Heparin