Agarose isoelectric focusing of plasma low and very low density lipoproteins using the PhastSystem

Human plasma lipoproteins, fractionated by density gradient ultracentrifugation, and very low density lipoproteins, subfractionated by cumulative rate centrifugation, were subjected to agarose isoelectric focusing in small format thin gels prepared in the laboratory for the commercially available PhastSystem (Pharmacia). From preparation of the gels to their staining, the procedure took less than 3 h. The pH gradient was found reproducible and the apparent average pI of individual low density lipoproteins could be measured with a coefficient of variation of less than 5% between and less than 2% within the same run. The method appears especially suitable for the exploration of charge properties of multiple lipoprotein samples, or other large macromolecules as low density lipoproteins and very low density lipoproteins, with considerable economy of time and reagents.