Preparation of Cæruloplasmin from the G2 Fraction of Human Plasma

Abstract

THE recent publication of a communication on the preparation of cæruloplasmin¹, the main cuproprotein of plasma, prompts this brief account of a method of its preparation from the precipitate G2, the mixture of α- and β-globulins obtained in the plasma fractionation scheme of Kekwick and Mackay². With G2 from batches of plasma of 40–150 l., the following stages were used: (1) Extraction of G2 by 0.07 M sodium chloride at pH7 and denaturation of extracted lipoprotein with ether below − 25° C. by the McFarlane technique³; (2) precipitation of cæruloplasmin from the ether-saturated extract at pH 4.8; (3) solution of the precipitate in ether-saturated 0.1 M sodium chloride, removal of impurities by precipitation at pH 5.35 and a second McFarlane treatment; (4) reprecipitation of cæruloplasmin at pH 4.8 as in (2) and solution in 0.1 M sodium chloride; (5) precipitation of impurities at pH 4.8 by diluting to 0.02 M sodium chloride and precipitation of cæruloplasmin by further dilution to 0.0045 M sodium chloride. The product was dissolved in 0.l M sodium chloride. E _{1 cm.} (605 mµ)/E _{1 cm.} (280 mµ), which gives a measure of degree of purification, was 0.019.