Rapid Micro Method for the Turbidimetric Determination of Serum Protein *

The significance of altered serum proteins in disease has long been recognized, but most of the current modes of analysis are either too complicated for routine use or yield unreliable data which are difficult to interpret. In a study of serum proteins for diagnostic purposes, it is essential to have a simple, inexpensive, but accurate procedure for complete protein analysis that will require only a small amount of serum and little time. Since no available technique fulfilled these criteria, we devised a rapid micro method for the turbidimetric analysis of serum which is convenient for clinical application. The method is based on a photoelectric measurement of the dispersed precipitate produced by (NH4)2S04 in highly dilute solutions of serum. Not only albumin and globulin, but the sub-fractions of globulin are precipitable with varying concentrations of the salt; hence, globulin may be fractionated into gamma, pseudo, and euglobulin with equal facility. When certain additional studies were made concerning the separation of acid insoluble proteins derived mainly from the globulin fractions, it was found that these were precipitable in acetate buffer at pH 5.1 and 6.0. In every instance, despite the method of precipitation, the protein concentration was estimated from the observed turbidity.