Ultracentrifugal studies of major non-lipide electrophoretic components of normal human serum.

In the ultracentrifuge, normal human serum shows, in addition to the lipoproteins, three distinct components with sedimentation rates of approximately 4, 7, and 19 Svedberg units (1, 2). Other materials known to be present are obscured by the high concentrations of these major substances and the high diffusion spreading of the boundaries. For example, Edsall (3) has reported a number of additional components in fractions separated by alcohol and salt precipitation. Likewise, several crystalline proteins have been isolated which show sedimentation rates different from the three mentioned above (4, 5). Electrophoresis reveals at least five major fractions, with probably a continuum of mobilities from the slowest y-globulin through the albumin. Since the transport behavior of a protein in an electric field is in general independent of its properties in an ultracentrifugal field, it becomes necessary to determine the distribution of the various sedimentation groups within each mobility fraction. The technique of moving boundary electrophoresis has not permitted the isolation of amounts of intermediate components sufficient to answer this question conveniently. However, with the introduction of various techniques of preparative zone electrophoresis, this type of approach has become feasible. Such studies on a number of fractions isolated from normal and pathological sera have been previously reported (6, 7). Recently, Brattsten has presented data on the sedimentation rates of some representative fract.ions of normal serum obtained by continuous zone electrophoresis (8). The present report attempts to ascertain the mobility distribution of all the major non-lipide proteins identified by their sedimentation rates. Because of the small number of sera studied, it has not been possible to specify exact “normal” levels of each of the serum component,s. However, the results may be useful, at least as a starting point, for more precise measurements of each mobility or sedimentation coefficient distribution, for