Determination of apolipoprotein variants by isoelectric focusing in agarose.

Isoelectric focusing (IEF) of apolipoproteins is an important procedure for the isolation of apolipoprotein isoforms. In this paper we describe the use of agarose/urea as a focusing medium for IEF of apolipoproteins. This technique, which offers several advantages over the traditional polyacrylamide gel focusing, yields a further microheterogeneity of the known isoforms of apolipoproteins A-I and E. In addition, by subsequent immunoprecipitation, both specificity and sensitivity are enhanced. Using a monospecific antiserum against Apo A-I, a new minor isoform was detected at the basic end of the Apo A-I spectrum (pI 6.02) which has not yet been observed in normal plasma samples. Another advantage of this technique in combination with immunoprecipitation is the specific detection of Apo E phenotypes which is essential for the diagnosis of hyperlipoproteinemia type III.