Precipitation Pattern of Serum Proteins in Phenylpyruvic Oligophrenia

Abstract

Jervis, et al., 1 have shown that the serum of phenylpyruvic oligo-phrenic individuals contains an abnormal amount of phenylalanine. In view of the recognized effects of small amounts of amino acids on the molecular dispersion of the proteins 2 it seemed possible that abnormalities in the state of the serum proteins might occur in this disease. Perlzweig, Kondritzer and Bruch 3 found that in pathological conditions fractional precipitation of the serum proteins with gradually increasing quantities of potassium phosphate at pH 6.5-6.8, according to Butler and Montgomery, 4 frequently reveals significant changes which are not brought out by the conventional methods for the determination of albumins and globulins by precipitation with an arbitrarily fixed concentration of a neutral salt.

In the present investigation the fractional precipitation procedure was applied to the serum proteins of 8 physically healthy patients in whom a diagnosis of phenylpyruvic oligophrenia had been made, and 8 healthy persons as controls. Nineteen portions of each sample of serum were precipitated with an equimolar KH₂PO₄-K₂HPO₄ buffer which ranged in molality from 1.2 to 3.0 mols in 0.1 mol increments. In 5 of the patients and 2 of the normal subjects 0.5 cc portions of freshly centrifuged serum were added to 15 cc portions of buffer (serum dilution 1:31). In the remaining experiments in which less serum was available the serum was diluted with an equal volume of physiological saline; then 0.5 cc portions were added to 10 cc portions of the buffer solutions (serum dilution 1:42). After standing overnight at room temperature the precipitate was filtered off and the total nitrogen in solution was determined (microkjeldahl) on a suitable aliquot. The value was corrected for the N.P.N., determined on a trichloracetic acid filtrate of the original serum, and the percentage of the total protein remaining in solution at each molality of phosphate was calculated.