Agarose gel electrophoresis of serum lipoproteins: determination of true mobility, isoelectric point, and molecular size

Abstract

The electrophoretic behavior of several proteins in agarose gel has been studied at different values of gel concentration, pH, and ionic strength. The proteins studied included serum low-density and very low-density lipoproteins (LDL and VLDL) obtained from a normal and a hyperlipemic person. Bovine serum albumin was also studied for comparison. Electrophoretic mobility M of all the proteins varied with gel concentration T, according to the relation log M/M₀=K_RT, where KR is a constant related to the size of the proteins. For bovine serum albumin (BSA) at different pH, the values of mobility obtained by extrapolation to zero gel concentration (M0) were found to be similar to those obtained by Schlessinger (12) by free boundary electrophoresis. A linear relationship was obtained between √K_R and the radius for the different proteins. From the M₀ values at different pH, the isoelectric points of LDL and VLDL isolated from the serum of a normolipemic person were found to be 5.20 and 4.30, respectively, at 0.05 ionic strength. The LDL and VLDL from the hyperlipemic person were shown to have the same size but different net charge in comparison to those of the normolipemic person.