Preparation of Control Sera for Fractionation of Lipoproteins in Human Serum

Compamtive Study of Liquid Nitrogen Frozen and Wieland's Methods

Abstract

We prepared two control sera for lipoprotein fractionation testing. The first was frozen in liquid nitrogen and the other was lyophilized with high concentrations of sucrose (wieland's method). This paper presents the electrophoretic and ultracentrifugal characteristics of these two sera.
1) The freezing temperature was critical in the liquid nitrogen method. In ser sera frozen at temperatures above-80°C, partial degradation of the lipoproteins was observed accompanied by a decrease in the pre-beta lipoprotein fraction and an increase in the beta lipoprotein fraction. Furthermore, parts of both fractions remained at the electrophoretic origin as an extra band.
No changes in electrophoretic patterns were observed, even in sera with abnormal lipoproteins, except for lipoprotein X. Liquid nitrogen freezing kept serum lipoproteins stable for 12 months.
2) Wieland's method required over 400mmol/l of sucrose to preserve the electrophoretic patterns of serum lipoproteins. Large quantities of lipoprotein X degraded and moved to the beta-lipoprotein fraction. Anyone who uses this must correct the concentrations of determinants by flame photometry.
Moreover, sera prepared by this method were unsuitable for HDL-cholesterol measurement by the heparin-manganese method. Lypohilized sera were stable for 10 months at -4°C.