Electrophoretic behaviour of pathological human serum albumins near pH 4

Abstract

Electrophoretic studies have been made of normal and pathological human serum albumins over the pH range 3.6–6.8 at 25°. The ionic strength of acetate or phosphate buffer used was 0.1 and the concentration of protein was 0.5% (g/100 ml). A single electrophoretic boundary occurred above pH 5.2, and two or three boundaries in the pH range 3.6–4.7. The area of each boundary changed continuously with pH; with increase in pH the area of the fast-moving boundary ( F form) decreased, while that of the slow-moving boundary ( N form) increased. (The F boundary was usually resolved into two boundaries under the conditions used). The change in area is interpreted by the isomerization equilibrium: N + nH + ah F, as in the case of bovine serum albumin. When albumins from normal subjects or from patients with mild diseases were used, n was 2 and the N and F forms existed in equal amounts at pH 4.10. When albumins from seriously ill patients were used, n was 3 and the N and F forms existed in equal amounts in the pH range 3.75–4.05; when these pathological albumins were used, the position of the isomerization curve was different in different diseases. Thus the percentage of N form at pH 4.10 was 50% for normal albumin but greater than 50% for abnormal albumins.