Application of zone centrifugation to the study of normal and pathological human sera

Abstract The development of a zone-centrifugation technique suitable for the fractionation of soluble protein mixtures such as human sera is described. This involves gradient differential sedimentation in buffered sucrose at 39,000 rpm in a swing-out rotor. Selection of optimum positions of slicing of the tubes (Lusteroid) after centrifugation is indicated by the use of reference proteins of various molecular sizes (4.5, 7, and 19 S ) labeled with different colored dyes. Pelleting of the high molecular weight (19 S ) components of serum is avoided by placing a layer of carbon tetrachloride on the bottom of the tube. Characteristic histograms, representative of serum ultracentrifugal composition, are obtained by plotting the optical densities (at 280 mμ) of fractions (zones) against their distance from the meniscus. It is, for example, possible to distinguish between myeloma and macroglobulinemic sera.