FRACTIONATION OF SERUM INTO ALBUMIN AND a-, /3-, AND r-GLOBULIN BY SODIUM SULFATE

The values of the albumin and total globulin of serum determined with 22.4 per cent sodium sulfate by the method of Howe (1) are better correlated with the values of one fraction containing the albumin and QIglobulin and of another containing the pand r-globulins (2). However, 19 per cent sodium sulfate seems to separate these fractions more efficiently, since it yields results which agree very well with the corresponding fractions determined by electrophoresis (3). Apparently the precipitation of all of the globulin fractions of human serum requires 26 to 27 per cent sodium sulfate (3,4). The data of Majoor (4) indicate that most of the r-globulin is precipitated by 15 per cent of the salt. This is consistent with the findings of Gutman et al. (5) that the r-globulin fraction is only partially precipitat,ed at a concentration of 13.5 per cent of the salt, while 17.4 per cent removes a significant amount of p-globulin in addition to the y fraction. Moreover, 15 per cent sodium sulfate is approximately equivalent to 0.33 saturated ammonium sulfate in respect to salting out. Jager and Nickerson found a good correlation between the amounts of protein precipitated by the latter and the values of r-globulin estimated by electrophoresis (6). Hence, it occurred to us that human serum can be analyzed for albumin and for all of the globulin fractions by determining the protein precipitated with 15, 19, and 26 per cent sodium sulfate. The present study was undertaken to determine whether the values estimated by this simple method are consistent with the results of other methods.