title: Simultaneous determination of the individual concentration gradients of two solute species in a centrifuged mixture: application to analytical ultracentrifugation.
abstract: A procedure for determining the absolute activity of 14C-labeled and 3H-labeled solutes in a mixture from the measured counts per minute in two scintillation energy windows is described. It is shown that the method described here provides a substantially more accurate determination of 3H activity in the presence of a larger 14C activity, and a more accurate determination of 14C activity in the presence of a larger 3H activity, than does the standard dual label analysis implemented in a Beckman LS 3801 scintillation counter. The new dual label procedure is combined with the automated fractionation procedure of Attri and Minton [(1986) Anal. Biochem. 152, 319-328] to permit the gradients of each of two differently radiolabeled solute species in a mixture to be individually determined following centrifugation. It is shown that the sedimentation coefficients of each of two differently labeled noninteracting proteins in a mixture may be readily determined in a sedimentation velocity experiment, and that the molecular weights of each of two such proteins in a mixture may be readily determined in a sedimentation equilibrium experiment.
mesh_terms: D002250:Carbon Radioisotopes; D002499:Centrifugation, Density Gradient; D008956:Models, Chemical; D008970:Molecular Weight; D011506:Proteins / Q000032:analysis*; D012996:Solutions / Q000032:analysis; D014316:Tritium; D014461:Ultracentrifugation
chemical_list: D002250:Carbon Radioisotopes; D011506:Proteins; D012996:Solutions; D014316:Tritium