EVALUATION OF COMMON ELECTROPHORETIC METHODS IN DETERMINING THE MOLECULAR-WEIGHT OF APOLIPOPROTEIN(A) POLYMORPHS

Five different gel systems were evaluated for their utility in determi ning the molecular weights of apolipoprotein(a) (apo(a)) polymorphs by SDS polyacrylamide or agarose gel electrophoresis. Three linear polya crylamide gradient gels (2-16% from Isolab (Akron, OH), 4-15% from Pha rmacia (Piscataway, NJ), and 2.5-6% homemade), a 4% polyacrylamide, an d a 1.5% agarose gel were examined. Crosslinked phosphorylase B oligom ers served as molecular weight standards. Molecular weights of four di fferent apo(a) polymorphs were determined in each gel system and compa red to values measured previously by sedimentation equilibrium. The re sults indicate that molecular weights obtained by gradient polyacrylam ide gel electrophoresis were within 10% and often not statistically di fferent from values acquired by sedimentation equilibrium. The use of homogenous 4% polyacrylamide and 1.5% agarose gels led to molecular we ights that were overestimated by 20 and 60-70%, respectively. ApoB(100 ), which is a commonly used molecular weight marker, was found to have anomalously fast mobility in each of the four polyacrylamide gel syst ems. Because its use would lead to overestimated apo(a) molecular weig hts, it was not useful as a molecular weight standard. Our results ind icate that SDS-gradient polyacrylamide gel electrophoresis with crossl inked phosphorylase B as standard is a suitable gel system for evaluat ing apo(a) molecular weights. (C) 1996 Academic Press, Inc.